Dissertations / Theses: 'Kelvin force probe microscopy'

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Ye, Sheng. "Kelvin Probe Force Microscopy (KPFM) for nanoelectronic device characterisation." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/419059/.

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This project is to develope a new method of characterization for Silicon-nano-wire (SiNW) FET and SET devices by using KPFM technology to derive the information of local surface potential change on the channel of SiNW devices. The surface potential is related to many important parameters on material's surface, e.g. fixed surface charge, doping profile variation, distribution of charge carriers under applied bias, and individual dopant atoms near the surface. Those parameters are strongly related to the characteristics of SiNW devices. The KPFM equipment is designed to extract the contact potential difference (CPD) between tip and sample. The change of CPD is related to the Fermi energy level in materials. Therefore any factors which induce Fermi energy level change inside material are detectable. The significantly improved lateral resolution (sub-nanometer) gives us confidence for the measurement of local surface potential variation. Much of the time has been dedicated for the KPFM equipment calibration and optimization. By the end of PhD project the surface potential characterisation of three different types of the silicon-nano-wire (SiNW) devices (uniformly doped SiNW, n-pn SiNW Field-Effect-Transistor (FET), and n-p-n-p-n SiNW Single-Electron-Transistor (SET)) has been achieved. By using surface potential information the surface traped charge and change in local resistivity in SiNW is successfully estimated and the result is confirmed well agreed with the characterisation of other conventional method. This characterisation result also suggest the accuracy of local surface potential measurement. In-situ potential mapping and proling of n-p-n FET channel under device operation has been successfully performed. By comparing the data with simulation and electrical characterisation of the same device, correspondence between the line-shape of the surface potential and electrical field profiles and device parameters has been clarified for the first time. An attempt has been made to observe the surface potential of the channel of SET devices which have shown clear Coulomb oscillation at low temperature (5K). The formation of a conductive channel in 330-nm-wide SiNW channel by the side gate modulation is successfully observed. Four main achievements can be claimed at the end of this project. First, the metallurgic p-n junction in thin (50nm) SOI has been first time ever detected by Ex curve extraction from measured potential profile and the Ex curve was used to study the charge transport in the n-p-n structure under different biasing condition. Secondary, the novel single side gate doping modulated single electron transistors was fabricated and shown Coulomb oscillations which was consistent with theoretical predictions. Furthermore, the operation of FET/SET was investigated by scanned high resolution surface potential profile which revealed the status of p-n junction under biasing. In the end, this study discovered a new method to investigate nano-electronic devices by KPFM scan and more information such as change in build-in voltage at low temperature, and charge in charge state of island can be extracted if the high vacuum and low temperature is applied.

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Murawski, Jan. "Time-Resolved Kelvin Probe Force Microscopy of Nanostructured Devices." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-224810.

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Since its inception a quarter of a century ago, Kelvin probe force microscopy (KPFM) has enabled studying contact potential differences (CPDs) on the nanometre scale. However, current KPFM investigations are limited by the bandwidth of its constituent electronic loops to the millisecond regime. To overcome this limitation, pump-probe-driven Kelvin probe force microscopy (pp-KPFM) is introduced that exploits the non-linear electric interaction between tip and sample. The time resolution surpasses the electronic bandwidth and is limited by the length of the probe pulse. In this work, probe pulse lengths as small as 4.5 ns have been realized. These probe pulses can be synchronized to any kind of pump pulses. The first system investigated with pp-KPFM is an electrically-driven organic field-effect transistor (OFET). Here, charge carrier propagation in the OFET channel upon switching the drain-source voltage is directly observed and compared to simulations based on a transmission line model. Varying the charge carrier density reveals the impeding influence of Schottky barriers on the maximum switching frequency. The second system is an optically-modulated silicon homojunction. Here, the speed of surface photovoltage (SPV) build-up is accessed and compared to timeaveraged results. Due to slow trap states, the time-averaged method is found to lack comprehensiveness. In contrast, pp-KPFM exposes two intensity-dependent recombination times on the same timescale — high-level Shockley-Read-Hall recombination in the bulk and heat-dominated recombination in the surface layer — and a delay of the SPV decay with rising frequency, which is attributed to charge carrier retention at nanocrystals. The third system is a DCV5T-Me:C60 bulk heterojunction. The SPV dynamics is probed and compared to measurements via open-circuit corrected transient charge carrier extraction by linearly increasing voltage. Both methods reveal an exponential onset of the band bending reduction that is attributed to the charge carrier diffusion time in DCV5T-Me, and a double exponential decay, hinting at different recombination paths in the studied organic solar cell. The above-mentioned experiments demonstrate that pp-KPFM surpasses conventional KPFM when it comes to extracting dynamic device parameters such as charge carrier retention and recombination times, and prove that pp-KPFM is a versatile and reliable tool for studying electrodynamics on nanosurfaces.

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Milde, Peter. "Visualisation of Local Charge Densities with Kelvin Probe Force Microscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-70867.

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For the past decades, Kelvin probe force microscopy (KPFM) developed from a sidebranch of atomic force microscopy to a widely used standard technique. It allows to measure electrostatic potentials on any type of sample material with an unprecedented spatial resolution. While the technical aspects of the method are well understood, the interpretation of measured data remains object of intense research. This thesis intends to prove an advanced view on how sample systems which are typical for ultrahigh resolution imaging, such as organic molecular submonolayers on metals, can be quantitavily analysed with the differential charge density model. In the first part a brief introduction into the Kelvin probe experiment and atomic force microscopy is given. A short review of the theoretical background of the technique is presented. Following, the differential charge density model is introduced, which is used to further explain the origin of contrast in Kelvin probe force microscopy. Physical effects, which cause the occurence of local differential charge densities, are reviewed for several sample systems that are of interest in high resolution atomic force microscopy. Experimental evidence for these effects is presented in the second part. Atomic force microscopy was used for in situ studies of a variety of sample systems ranging from pristine metal surfaces over monolayer organic adsorbates on metals to ferroelectric substrates both, with and without organic thin film coverage. As the result from these studies, it is shown that the differential charge density model accurately describes the experimentally observed potential contrasts. This implies an inherent disparity of the measurement results between the different Kelvin probe force microscopy techniques; a point which had been overseen so far in the discussion of experimental data. Especially for the case of laterally strong confined differential charge densities, the results show the opportunity as well as the necessity to explain experimental data with a combination of ab initio calculations of the differential charge density and an electrostatic model of the tip-sample interaction.

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Ruiz, Ortega Leonardo Ibor. "Micropatterns for surface potential mapping of biomolecules by Kelvin probe force microscopy." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/micropatterns-for-surface-potential-mapping-of-biomolecules-by-kelvin-probe-force-microscopy(2a7d9300-f575-4786-b9a3-600e807cd66c).html.

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Current methods to detect and quantify electrostatic properties of biomolecules, nowadays, still facing many challenges. For instance, they are not sensitive enough to meet the needs of more precise measurements, they require the use of external markers or antibodies, or rely on indirect calculations or models such is the case for zeta potential and electrophoretic mobility. However, Kelvin probe force microscopy (KPFM) have gained attention due to its expanding possibilities to asses electrostatic properties of biomolecules. Among the advantages that KPFM possess over other methods, stands out its high sensitivity and spatial resolution. Moreover, it does not require the use of external labels. In the interest of establishing a method for mapping surface potential of biomolecules by means of Kelvin probe force microscopy, two techniques of poly-dimethylsiloxane (PDMS) soft lithography for micro-patterning (micro channel filling and micro contact printing) are studied. Similarly, the possibility of patterning biomolecules on different substrates (mica, glass and silicon dioxide) is explored. Primarily, poly-L-lysine was used as a model biomolecule due to the exposure of amino functional groups. Different physicochemical conditions on poly-Llysine micro patterns were tested in order to assess the suitability of soft lithography combined with KPFM to measure electrostatic properties of biomolecules. In this sense, continuous KPFM scans, immersions in water, lift height and time dependence were investigated. Moreover, due to the importance of the understanding of the effects of exposure of biomolecules to elevated levels of sugars, immersions in D-ribose were performed. A concentration dependent effect was observed, affecting drastically the surface potential of polyL-lysine. Electrostatically driven patterning of colloidal gold nanoparticles was also achieved on pol-L-lysine micro patterns, resulting in a good method for marking the presence of pol-Llysine and opening the possibility to improve some properties of nanoparticle systems. Besides microchannel filling, micro contact printing of poly-L-lysine was successfully achieved on mica, glass and silicon dioxide, resulting in better quality micro patterns and understanding of the influence of using different substrates on surface potential. On this regard, continuous KPFM scans revealed a surface charge dynamic on mica, whereas on glass and silicon dioxide surface potential became more stable. Insulin, BSA and β-lactoglobulin were successfully patterned on mica by micro contact printing and imaged by KPFM. Response to pH and immersions in water was investigated showinga clear reversible shift on surface potential. Similarly, cross-patterning of different proteins on the same substrate for surface potential oneto-one comparison was successfully achieved. The classic case of avidin-biotin complex was also investigated byboth fluorescence optical microscopy and KPFM. Finally, in an attempt to stretch the applications of KPFM for surface potential mapping of biomolecules, insulin amyloid fibrils were co-fibrillated with highly charge nanoparticles. Surface potential maps of amyloid structures were achieved and the effect of continuous scanning on surface potential was assessed.

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Bostanci, Umut. "Development Of Atomic Force Microscopy System And Kelvin Probe Microscopy System For Use In Semiconductor Nanocrystal Characterization." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608812/index.pdf.

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Atomic Force Microscopy (AFM) and Kelvin Probe Microscopy (KPM) are two surface characterization methods suitable for semiconductor nanocrystal applications. In this thesis work, an AFM system with KPM capability was developed and implemented. It was observed that, the effect of electrostatic interaction of the probe cantilever with the sample can be significantly reduced by using higher order resonant modes for Kelvin force detection. Germanium nanocrystals were grown on silicon substrate using different growth conditions. Both characterization methods were applied to the nanocrystal samples. Variation of nanocrystal sizes with varying annealing temperature were observed. Kelvin spectroscopy measurements made on nanocrystal samples using the KPM apparatus displayed charging effects.

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Baumgart, Christine. "Quantitative dopant profiling in semiconductors: A new approach to Kelvin probe force microscopy." Forschungszentrum Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-97372.

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Failure analysis and optimization of semiconducting devices request knowledge of their electrical properties. To meet the demands of today’s semiconductor industry, an electrical nanometrology technique is required which provides quantitative information about the doping profile and which enables scans with a lateral resolution in the sub-10 nm range. In the presented work it is shown that Kelvin probe force microscopy (KPFM) is a very promising electrical nanometrology technique to face this challenge. The technical and physical aspects of KPFM measurements on semiconductors required for the correct interpretation of the detected KPFM bias are discussed. A new KPFM model is developed which enables the quantitative correlation between the probed KPFM bias and the dopant concentration in the investigated semiconducting sample. Quantitative dopant profiling by means of the new KPFM model is demonstrated by the example of differently structured, n- and p-type doped silicon. Additionally, the transport of charge carriers during KPFM measurements, in particular in the presence of intrinsic electric fields due to vertical and horizontal pn junctions as well as due to surface space charge regions, is discussed. Detailed investigations show that transport of charge carriers in the semiconducting sample is a crucial aspect and has to be taken into account when aiming for a quantitative evaluation of the probed KPFM bias.

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Fratelli, Ilaria. "Flexible oxide thin film transistors: device fabrication and kelvin probe force microscopy analysis." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13538/.

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I transistor a film sottile basati su ossidi amorfi semiconduttori sono ottimi candidati nell'ambito dell'elettronica su larga scala. Al contrario delle tecnologie basate su a-Si:H a poly-Si, gli AOS presentano un'elevata mobilità elettrica (m > 10 cm^2/ Vs) nonostante la struttura amorfa. Inoltre, la possibilità di depositare AOS a basse temperature e su substrati polimerici, permette il loro impiego nel campo dell'elettronica flessibile. Al fine di migliorare questa tecnologia, numerosi TFT basati su AOS sono stati fabbricati durante 4 mesi di attività all'Università Nova di Lisbona. Tutti i transistor presentano un canale formato da a-GIZO, mentre il dielettrico è stato realizzato con due materiali differenti: Parylene (organico) e 7 strati alternati di SiO2 e SiO2 + Ta2O5. I dispositivi sono stati realizzati su substrati flessibili sviluppando una nuova tecnica per la laminazione e la delaminazione di fogli di PEN su supporto rigido. L'ottimizzazione del processo di fabbricazione ha permesso la realizzazione di dispositivi che presentano caratteristiche paragonabili a quelle previste per TFT costruiti su substrati rigidi (m = 35.7 cm^2/Vs; VON = -0.10 V; S = 0.084 V/dec). Al Dipartimento di Fisica dell'UNIBO, l'utilizzo del KPFM ha permesso lo studio a livello microscopico delle prestazioni presentate dai dispositivi analizzati. Grazie a questa tecnica di indagine, è stato possibile analizzare l'impatto delle resistenze di contatto sui dispositivi meno performanti e identificare l'esistenza di cariche intrappolate nei TFT basati su Parylene. Gli ottimi risultati ottenuti dall'analisi KPFM suggeriscono un futuro impiego di questa tecnica per lo studio del legame tra stress meccanico e degradazione elettrica dei dispositivi. Infatti, la comprensione dei fenomeni microscopici dovuti alla deformazione strutturale sarà un passaggio indispensabile per lo sviluppo dell'elettronica flessibile.

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Baumgart, Christine. "Quantitative dopant profiling in semiconductors: A new approach to Kelvin probe force microscopy." Helmholtz-Zentrum Dresden-Rossendorf, 2012. https://hzdr.qucosa.de/id/qucosa%3A22160.

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Failure analysis and optimization of semiconducting devices request knowledge of their electrical properties. To meet the demands of today’s semiconductor industry, an electrical nanometrology technique is required which provides quantitative information about the doping profile and which enables scans with a lateral resolution in the sub-10 nm range. In the presented work it is shown that Kelvin probe force microscopy (KPFM) is a very promising electrical nanometrology technique to face this challenge. The technical and physical aspects of KPFM measurements on semiconductors required for the correct interpretation of the detected KPFM bias are discussed. A new KPFM model is developed which enables the quantitative correlation between the probed KPFM bias and the dopant concentration in the investigated semiconducting sample. Quantitative dopant profiling by means of the new KPFM model is demonstrated by the example of differently structured, n- and p-type doped silicon. Additionally, the transport of charge carriers during KPFM measurements, in particular in the presence of intrinsic electric fields due to vertical and horizontal pn junctions as well as due to surface space charge regions, is discussed. Detailed investigations show that transport of charge carriers in the semiconducting sample is a crucial aspect and has to be taken into account when aiming for a quantitative evaluation of the probed KPFM bias.

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Narvaez, Gonzalez Angela Carolina. "Nanofios semicondutores : análise de propriedades elétricas e estruturais por microscopia no modo Kelvin Probe." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278455.

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Orientador: Monica Alonso Cotta
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Made available in DSpace on 2018-08-11T21:43:56Z (GMT). No. of bitstreams: 1 NarvaezGonzalez_AngelaCarolina_M.pdf: 14145813 bytes, checksum: 31ac8f1ebde240684c9bbe88b9c9b7a7 (MD5) Previous issue date: 2008
Resumo: As propriedades elétricas de nanofios (InAs, InP, InP-InAs-InP, InAsP) individuais e em junções foram estudadas implementando simultaneamente as técnicas Non Contact Atomic Force Microscopy NC-AFM (para aquisição da topografia) e Amplitude-sensitive Modulated Kelvin Probe Microscopy AM-KPFM (fornece medidas do Potencial de Superfície), permitindo correlacionar as propriedades elétricas com a estrutura da amostra. Em particular, o comportamento do Potencial de Superfície (PS) em função do diâmetro do nanofio foi investigado e utilizado na identificação do material que o compõe. Em uma primeira etapa, a técnica AM-KPFM foi caracterizada, principalmente em termos de resolução para análise de nano-objetos. Nossos resultados evidenciaram um fator de escala presente associado à eletrônica do equipamento, que somente permitiu realizar uma análise qualitativa dos dados adquiridos. Além disso, foi observada uma diminuição no contraste nas medidas elétricas quando o tamanho do objeto analisado diminui. Medidas em nanofios individuais de InP e InAs permitiram estabelecer que há uma queda no PS quando o diâmetro do fio diminui. Este comportamento é o resultado de duas contribuições: a perda no contraste (efeito de tamanho na medida) e o incremento local da função trabalho, que poderíamos associar ao aumento da proporção entre a carga superficial e a carga no interior do fio. Nas junções, há um aumento no PS na região da junção, indicando a formação de uma barreira de energia associada à acumulção de carga. Isto isola as junções do comportamento típico observado em nanofios individuais. Medidas em junções montadas em dispositivos poderiam complementar o estudo deste tipo de configurações. A caracterização do PS em função do diâmetro para os nanofios de InP e InAs permitiu a identificação do material (InAs ou InP) presente ao longo dos fios heteroestruturados de InP-InAs-InP, mostrando também a presença da nanopartícula de ouro usada como catalisador no crescimento. Os contrastes no PS ao longo do fio não se correlacionam diretamente às imagens de Microscopia Eletrônica de Transmissão, sugerindo que a interface elétrica é diferente da metalúrgica. Nos nanofios de InAsP, pelo contrário, os dados obtidos indicam a formação de uma liga ternária
Abstract: The electric properties of InAs, InP, InP-InAs-InP and InAsP nanowires (NWs) -assembled both individually and in junctions - were studied by simultaneous imple-mentation of Non Contact Atomic Force Microscopy NC-AFM (for topography) and Amplitude-sensitive Modulated Kelvin Probe Microscopy AM-KPFM (for Surface Potential distribution), obtaining spatially resolved electrical measurements of the sample structure. In particular, the SP vs NW diameter behavior was investigated and used to identify the material composing the nanowires. In a first approach, AM-KPFM was characterized mainly in terms of resolution for the analysis of the nano-objects. Our results suggest there is a scale factor on our measurements associated to the equipment electronics, that limited our discussion to a qualitative interpretation of the acquired data. Also, a contrast decrease on SP measurements was observed when the size of the object is reduced, comparatively to the tip. The experimental results on individual InAs and InP nanowires showed a SP saturation level (SPsat) below which SP drops with the NW diameter. This behavior came from at least two contributions: a loss of SP contrast due to object/tip size effects and a local increment on work function, that we associate to the larger surface/volume ratio close to the NW tip which makes the material more intrinsic. For NWs on junctions, a larger SP value is correlated to the regions where the junction is formed, possibly due to charge accumulation. Measurements of junctions assembled on devices could complement the study of this kind of structures. The SP vs diameter characterization of InAs and InP nanowires also allowed the identification of the material along the heterostructured InP-InAs-InP nanowire, showing the presence of the Au nanoparticle used to catalyze the growth. The SP image is not directly correlated with HR-TEM images, suggesting that electric and metallurgic interfaces are not the same. For InAsP nanowires, the acquired data indicate the formation of an homogeneous ternary alloy
Mestrado
Física da Matéria Condensada
Mestre em Física

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Romero, Lairado Francisco [Verfasser]. "Preparation and interpretation of Kelvin probe force microscopy experiments on bulk insulators / Francisco Romero Lairado." Mainz : Universitätsbibliothek Mainz, 2018. http://d-nb.info/1168757908/34.

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Travaglini, Lorenzo. "In-situ detection of defect formation in organic flexible electronics by Kelvin Probe Force Microscopy." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10380/.

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Organic semiconductor technology has attracted considerable research interest in view of its great promise for large area, lightweight, and flexible electronics applications. Owing to their advantages in processing and unique physical properties, organic semiconductors can bring exciting new opportunities for broad-impact applications requiring large area coverage, mechanical flexibility, low-temperature processing, and low cost. In order to achieve highly flexible device architecture it is crucial to understand on a microscopic scale how mechanical deformation affects the electrical performance of organic thin film devices. Towards this aim, I established in this thesis the experimental technique of Kelvin Probe Force Microscopy (KPFM) as a tool to investigate the morphology and the surface potential of organic semiconducting thin films under mechanical strain. KPFM has been employed to investigate the strain response of two different Organic Thin Film Transistor with active layer made by 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-Pentacene), and Poly(3-hexylthiophene-2,5-diyl) (P3HT). The results show that this technique allows to investigate on a microscopic scale failure of flexible TFT with this kind of materials during bending. I find that the abrupt reduction of TIPS-pentacene device performance at critical bending radii is related to the formation of nano-cracks in the microcrystal morphology, easily identified due to the abrupt variation in surface potential caused by local increase in resistance. Numerical simulation of the bending mechanics of the transistor structure further identifies the mechanical strain exerted on the TIPS-pentacene micro-crystals as the fundamental origin of fracture. Instead for P3HT based transistors no significant reduction in electrical performance is observed during bending. This finding is attributed to the amorphous nature of the polymer giving rise to an elastic response without the occurrence of crack formation.

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Grover, Ranjan. "Characterizing Thermal and Chemical Properties of Materials at the Nanoscale Using Scanning Probe Microscopy." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195932.

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Current magnetic data storage technology is encountering certain fundamental limitations that present roadblocks to its scalability to areal densities of 1 Tbit/in^2 and beyond. Next generation magnetic storage technology is expected to use optical near field techniques to heat the magnetic film locally to write data bits. This requires experimental measurement of thermal conductivity of materials with sub--100 nm resolution. This is essential for the tailoring of the thin film stack to optimize the heat transfer of the process. This can be accomplished with a simple modification to a traditional atomic force microscopy (AFM) system. The modification requires the deposition of a thin metal film on the AFM cantilever thus creating a bimetallic cantilever. The curvature of a bimetallic cantilever is sensitive to temperature. Another modification is the use of a heating laser to raise the temperature of the cantilever so that when it scans across a sample with areas of varying thermal conductivity the bimetallic deformation of the heated cantilever is altered. The resulting system is sensitive to local variations in thermal conductivity with nanoscale resolution. Nanoscale thermal conductivity measurements can then be used to optimize the heat transfer properties of the materials used in a heat assisted magnetic recording system. AFM technology can also play a key role in the development of next generation solid-state chemical sensors. An AFM can be used to measure the workfunction of a material with near atomic resolution thus enabling the study of chemical reactions with high spatial resolution. Since chemical sensors typically use a chemical reaction at their front end to monitor the prescience of a gas, an AFM system can thus be used to understand and optimize the properties of the chemical reaction by monitoring the local workfunction. In this thesis, I explain the use of atomic force microscopy in measuring thermal and chemical properties of materials with applications towards the magnetic storage industry and chemical sensing.

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Narchi, Paul. "Investigation of crystalline silicon solar cells at the nano-scale using scanning probe microscopy techniques." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX085/document.

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Cette thèse s’intéresse à l’analyse de cellules silicium cristallin à l’échelle nanométrique, à l’aide de techniques de microscopie à sonde locale (SPM). En particulier, nous avons choisi d’analyser les propriétés électriques à l’échelle locale, grâce à deux techniques SPM : la microcopie à sonde de Kelvin (KPFM) et la microscopie à force atomique à sonde conductrice (CP-AFM).Tout d’abord, nous présentons les forces et faiblesses de ces deux techniques, comparées à la microscopie électronique, qui permet également d’analyser les propriétés électrique à l’échelle nanométrique. Cette comparaison approfondie nous permet d’identifier des mesures où le KPFM et le CP-AFM sont particulièrement adéquat et peuvent apporter de la valeur. Ces mesures sont divisées en deux catégories : les analyses matériaux et les analyses dispositifs.Ensuite, nous nous focalisons sur les analyses matériaux à l’échelle nanométrique. Nous présentons d’abord des mesures de dopage à l’échelle nanométrique, à l’aide d’une technique avancée de CP-AFM, appelée Resiscope. Nous montrons que cette technique peut détecter des changements de dopage dans la gamme 1015 à 1020 atomes.cm-3, avec une résolution nanométrique et un bon ratio signal/bruit. Puis, nous présentons des mesures de durée de décroissance sur des wafers silicium cristallin passivés. Les mesures sont réalisées sur la tranche non-passivée des échantillons. Nous montrons que, même si la tranche n’est pas passivée, les durées de décroissance obtenue par KPFM ont une bonne corrélation avec les temps de vie des wafers mesurées par décroissance de la photoconductivité détectée par micro-ondes.Par la suite, nous nous concentrons sur les analyses dispositif. A l’aide du KPFM, nous analysons deux types de cellules solaires silicium cristallin : les cellules solaires silicium épitaxié (epi-Si) et les cellules solaires hétérojonctions à contact arrière (IBC). En particulier, nous nous focalisons sur l’analyse de dispositifs en condition d’opération. Nous étudions d’abord l’influence de la tension électrique appliquée et nous montrons que les effets de résistance et de diode peuvent être détectés à l’échelle nanométrique. Les mesures de KPFM sont comparées aux mesures de microscopie électronique à balayage (SEM) dans les mêmes conditions, puisque le SEM est aussi sensible au potentiel de surface. Nous montrons que les mesures KPFM sur la tranche de cellules solaires epi-Si peuvent permettre d’étudier les changements de champ électrique avec la tension électrique appliquée. De plus, si la tension électrique est modulée en fréquence, nous montrons que des mesures de temps de vie peuvent être effectuées à l’échelle locale sur la tranche de cellules solaires epi-Si, ce qui peut permettre de détecter les interfaces limitantes. Puis, nous étudions l’influence de l’illumination sur les mesures KPFM et CP-AFM. Nous effectuons des mesures sur la tranche de cellules epi-Si sous différentes valeurs d’intensité et longueurs d’onde d’illumination. Nous montrons une bonne sensibilité des mesures KPFM à l’illumination. Cependant, nous montrons que pour différentes longueurs d’onde, à tension de circuit ouvert fixé, nos mesures ne sont pas corrélées avec les mesures de rendement quantique interne, comme nous le pensions.Enfin, nous résumons notre travail dans un tableau qui représente les forces et faiblesses des techniques pour les différentes mesures d’intérêt exposées précédemment. A partir de ce tableau, nous imaginons un setup de microscopie « idéal » qui permette d’analyser les cellules solaires de manière fiable, versatile et précise. Pour finir, nous proposons des mesures d’intérêt qui pourraient être réalisées avec ce setup « idéal »
This thesis focuses on the investigation of crystalline silicon solar cells at the nano-scale using scanning probe microscopy (SPM) techniques. In particular, we chose to investigate electrical properties at the nano-scale using two SPM techniques: Kelvin Probe Force Microscopy (KPFM) and Conducting Probe Atomic Force Microscopy (CP-AFM).First, we highlight the strengths and weaknesses of both these techniques compared to electron microscopy techniques, which can also help investigate electrical properties at the nano-scale. This comprehensive comparison enables to identify measurements where KPFM and CP-AFM are particularly adequate. These measurements are divided in two categories: material investigation and devices investigation.Then, we focus on materials investigation at the nano-scale using SPM techniques. We first present doping measurements at the nano-scale using an advanced CP-AFM technique called Resiscope. We prove that this technique could detect doping changes in the range 1015 and 1020 atoms.cm-3 with a nano-scale resolution and a high signal/noise ratio. Then, we highlight decay time measurements on passivated crystalline silicon wafers using KPFM. Measurements are performed on the unpassivated cross-section. We show that, even though the cross-section is not passivated, decay times measurements obtained with KPFM are in good agreement with lifetimes measured by microwave photoconductivity decay.Subsequently, we focus on device measurements. Using KPFM, we investigate two different crystalline silicon solar cell architectures: epitaxial silicon (epi-Si) solar cells and interdigitated back contact (IBC) heterojunction solar cells. In particular, we focus on measurements on devices under operating conditions. We first study the influence of the applied electrical bias. We study the sensitivity of surface potential to electrical bias and we show that diode and resistance effects can be detected at the nano-scale. KPFM measurements are compared to scanning electron microscopy (SEM) measurements in the same conditions since SEM is also sensitive to surface potential. We show that KPFM measurements on the cross-section of epi-Si solar cells can help detect electric field changes with electrical bias. Besides, if the electrical bias is frequency modulated, we show that lifetime measurements can be performed on the cross-section of epi-Si solar cells and can help detect limiting interfaces and layers. Then, we study the influence of illumination on KPFM and CP-AFM measurements. We perform photovoltage and photocurrent measurements on the cross-section of epi-Si solar under different values of illumination intensity and illumination wavelength. We show a good sensitivity of KPFM measurements to illumination. However, we show that measurements for different wavelengths at a given open circuit voltage, are not correlated with the internal quantum efficiency, as we could have expected.Finally, we summarize our work in a table showing the impact of strengths and weaknesses of the techniques for the different measurements highlighted. From this table, we imagine an “ideal” microscopy setup to investigate crystalline silicon solar cells in a reliable, versatile and accurate way. We propose investigations of interest that could be carried out using this “ideal” setup

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Murawski, Jan [Verfasser], Lukas M. [Akademischer Betreuer] Eng, and Björn [Gutachter] Lüssem. "Time-Resolved Kelvin Probe Force Microscopy of Nanostructured Devices / Jan Murawski ; Gutachter: Björn Lüssem ; Betreuer: Lukas M. Eng." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1133109640/34.

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Murawski, Jan [Verfasser], Lukas M. Akademischer Betreuer] Eng, and Björn [Gutachter] [Lüssem. "Time-Resolved Kelvin Probe Force Microscopy of Nanostructured Devices / Jan Murawski ; Gutachter: Björn Lüssem ; Betreuer: Lukas M. Eng." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-224810.

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Remmert, Jessica Lynn. "Nano Thermal and Contact Potential Analysis with Heated Probe Tips." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14585.

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This work describes two closed-loop atomic force microscopy methods that utilize the heated silicon probe to interrogate surfaces. The first method identifies the softening temperatures of a selected polymer and organic substrate as a function of contact force and surface hardness. Motivation partly stems from nanosampling, which requires knowledge of phase-specific transitions to identify and extract mass from multicomponent systems for chemical analysis. In the second method, the cantilever is implemented as a Kelvin probe to study the effect of temperature on the measured contact potential. The objective is to ascertain whether the probe functions as a capable electrode for scanning Kelvin probe microscopy (SKPM) applications. This was achieved by performing heated force-distance experiments on a biased gold film with the tip operating at various potentials. Both experiments examine the interaction between the tip and substrate and analyze sample effects both induced and sensed by the cantilever.

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Alvarado, Chavarin Carlos [Verfasser], and Gerd [Akademischer Betreuer] Bacher. "Investigation of electrical contact resistances in graphene-based devices by Kelvin Probe Force Microscopy / Carlos Alvarado Chavarin ; Betreuer: Gerd Bacher." Duisburg, 2017. http://d-nb.info/1133478905/34.

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18

Fernandez, Garrillo Pablo Arturo. "Développement de techniques de microscopie Kelvin hautement résolues et photomodulées pour l'étude de systèmes photovoltaïques." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY031/document.

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Cette thèse propose, décrit et utilise un ensemble de techniques basées sur la microscopie à force atomique sous ultravide pour la cartographie simultanée, à l'échelle nanométrique, de la topographie de surface et des dynamiques temporelles des photo-porteurs. Ainsi, en contrôlant la dépendance du photo-potentiel de surface moyen mesuré par microscopie à force de sonde Kelvin en fonction de la fréquence de répétition d'une source lumineuse externe d'excitation, le dispositif expérimental permet d’accéder aux dynamiques temporelles du photo-potentiel de surface qui, à leur tour, permettent d'étudier les dynamiques des photo-porteurs sur une large gamme d'échantillons. Afin de permettre le processus de nano-imagerie bidimensionnelle, ces mesures sont acquises de manière répétée en enregistrant des courbes spectroscopiques en chaque point d’une grille prédéfinie. En utilisant une procédure d'ajustement mathématique automatique, les dynamiques temporelles des photo-porteurs sont extraites à partir des données expérimentales.Cet ensemble de nouvelles méthodes est utilisé pour l’étude de plusieurs types d'échantillons issus de différentes technologies photovoltaïques telles que des couches minces en silicium poly-cristallin à petits grains, des cellules de troisième génération à nano cristaux de silicium, des cellules photovoltaïques organiques et des cellules à base de matériaux de structure pérovskite. Dans chaque cas, on décrit les processus de recombinaison des photo-porteurs ainsi que leur lien avec la morphologie et la structuration du matériau. Enfin, les aspects techniques de ces nouvelles méthodes d’analyse sont présentés, ainsi que leurs limites, notamment celles concernant l'interprétation des résultats
This thesis is directed towards the proposition and demonstration of a set of novel advanced atomic force microscopy based techniques under ultra-high vacuum conditions, enabling to map simultaneously the surface topography and the photo-carrier dynamics at the nanometre scale. In fact, by monitoring the dependence of the average surface photo-voltage measured with Kelvin probe force microscopy, as a function of the repetition frequency of a modulated excitation source, we will access the built-up and decay dynamics of the surface photo-voltage response which in turn will allows us to study the photo-carrier dynamics over a wide range of samples. In order to enable the 2-dimensional nano-imaging process, Kelvin probe force microscopy under modulated illumination measurements are acquired repeatedly over each point of a predefined grid area over the sample acquiring a set of spectroscopy curves. Then, using an automatic mathematical fit procedure, spectroscopy curves are translated into pixels of the photo-carrier dynamic time-constant images.Moreover, these set of novel techniques will be used to investigate the surface photo-voltage dynamics in several kinds of photovoltaic samples from different technological branches such as small grain polycrystalline silicon thin films, silicon nanocrystal-based third generation cells, bulk heterojunction donor-acceptor organic photovoltaics and organic-inorganic hybrid perovskite single crystal cells, discussing in each case the photo-carrier recombination process and its relation with the material’s structuration/morphology. Finally, technical aspects of these novel techniques will be discussed as well as their limitations and remaining open question regarding results interpretation

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Milde, Peter [Verfasser], Lukas M. [Akademischer Betreuer] Eng, and Christian [Akademischer Betreuer] Loppacher. "Visualisation of Local Charge Densities with Kelvin Probe Force Microscopy / Peter Milde. Gutachter: Lukas M. Eng ; Christian Loppacher. Betreuer: Lukas M. Eng." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://d-nb.info/1067189939/34.

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20

Mojrová, Barbora. "Využití měřicí metody SPM v technologii výroby krystalických solárních článků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220108.

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This thesis deals with the use of Atomic Force Microscopy (AFM) and Kelvin Probe Force Microscopy (KPFM) in solar cells production. Both techniques measure surface properties using interactions between surface and tip that progressively scans entire surface of the sample. Atomic force microscopy allows three dimensional imaging of surface structure. Kelvin probe force microscopy is used to measure the contact potential difference on the sample surface. There are described experimental measurements of monocrystalline and multicrystalline substrates after various etching processes using AFM. By using KPFM the contact potential difference was measured on dielectric layers PSG, SiOX, SiNX and Al2O3 and on selective emitter structures. All experiments described in this work were carried out at the Solartec Ltd. workplace and they completely correspond with the actual technology of crystalline solar cells production.

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López, Elvira Elena. "Desarrollo de un sistema combinado de microscopía óptica y microscopía de fuerzas." Doctoral thesis, Universidad de Murcia, 2013. http://hdl.handle.net/10803/117602.

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En este trabajo se ha desarrollado un microscopio de fuerzas (SFM) provisto de microscopía electrostática (ESFM) y microscopía Kelvin (KPM) especialmente diseñado para integrarse en un microscopio óptico invertido de forma que combine simultáneamente las técnicas de campo cercano con las técnicas ópticas. Tras una introducción (capítulo 1) y la descripción de las técnicas experimentales (capítulo 2), se detallan las características del diseño de un primer prototipo, así como las medidas realizadas con él con el fin de comprobar su correcto funcionamiento (capítulo 3). El capítulo 4 muestra el diseño de un segundo prototipo con las mejoras que incorpora respecto al primero, que lo convierten en un sistema más completo, versátil y fácil de manejar. También figuran las medidas realizadas con él. El capítulo 5 muestra un estudio de fotodegradación en polímeros conductores en función de la radiación incidente, combinando microscopía electrostática y Kelvin con técnicas ópticas.
In this work we have developed an Scanning Force Microscope (SFM) equipped with Electrostatic and Kelvin Probe Microscopy (ESFM, KPM), specially designed for integration into an inverted optical microscope in order to combine near-field techniques with optical techniques. After an introduction (Chapter 1) and the description of the experimental techniques (Chapter 2), are described the features of the design of a first prototype, as well as the measurements made with it in order to verify proper operation (Chapter 3). The Chapter 4 shows the design of a second prototype that incorporates the improvements over the first, making it more comprehensive, versatile and easy to handle. Also are shown the measurements performed with it. The Chapter 5 shows a photodegradation study of conductive polymers as a function of incident radiation combining KPM with optical techniques.

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Seiss, Martin. "Caractérisation des processus élémentaires de croissance des cristaux de carbure de silicium non désorienté." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00965640.

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Le carbure de silicium est un semiconducteur prometteur pour les applications en électronique de température et de haute puissance. La croissance de SiC a été améliorée continuellement pendant les derniers années mais la connaissance des processus à la surface pendant la croissance est encore faible. Dans cette thèse ces processus sont étudiés par l'analyse de la croissance initiale de cristaux non désorientés. Le processus qui limite la vitesse de croissance est déterminé. L'étude des germes observés occasionnellement permet d'avoir un aperçu des barrières Ehrlich-Schwoebel existantes et, de plus, d'estimer l'ordre de grandeur de la longueur de diffusion à la surface. Pour la première fois les lois de croissance de spirales sont systématiquement analysées sur la face silicium et la face carbone du SiC. L'influence d'un domaine limité et du chevauchement de champs de diffusion sur la forme des spirales et les lois de croissance sont analysées par des simulations. Sur les spirales de la face carbone, une nouvelle structure de marches est observée. La bicouche supérieure se dissocie à certaines conditions définies et reproductibles. Les conditions expérimentales sont clairement identifiées et une analyse de cette nouvelle structure est effectuée.

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Marchat, Clément. "Caractérisation électrique et optoélectronique de nouveaux matériaux et composants photovoltaïques à partir de techniques AFM." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS094.

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Cette thèse s’intéresse à la caractérisation des propriétés électriques des dispositifs photovoltaïques (PV) par deux techniques de microscopie à sonde locale : la microscopie à force atomique à pointe conductrice (c-AFM) et la microscopie à sonde de Kelvin (KPFM). Elle commence par une étude sur le silicium cristallin, et plus spécifiquement sur l’influence des états de surface sur la mesure KPFM. Cette dernière a été réalisée à l’obscurité et sous éclairement dans le but d’extraire le photovoltage de surface (SPV). Cette étude expérimentale a été complétée avec de la simulation numérique. Dans une deuxième étude nous avons caractérisé des dispositifs PV à nanofils. Il s’agit de jonctions radiales PIN en silicium amorphe hydrogéné réalisées sur des nanofils de silicium cristallin fortement dopé qui ont été étudiées par KPFM et SPV. Nous avons ainsi pu montrer que sur des dispositifs à nanofils recouverts d’ITO, la mesure de SPV permet de mesurer la tension de circuit-ouvert (Voc). Cette même mesure appliquée sur des nanofils uniques (sans contact ITO en face avant) est fortement influencée par l’ombrage de la pointe AFM et par les états de surface de la couche en silicium amorphe. Enfin nous nous sommes intéressés aux contacts passivants (poly-Si/SiOx/c-Si). Les caractérisations KPFM ont révélé des cartographies de potentiel de surface très homogènes en l’absence de la couche enterrée de SiOx, alors que de nombreuses zones de diamètre inférieur au micron présentent des valeurs de potentiel de surface plus faibles lorsque la couche de SiOx est incorporée dans la structure. Ces résultats semblent compatibles avec la présence d’inhomogénéités structurelles de taille nanométrique (pinholes) dans la couche de SiOx
This thesis focuses on the characterisation of electrical properties of photovoltaic devices by using two scanning probe techniques: conductive atomic force microscopy (c-AFM) and Kelvin probe force microscopy (KPFM). It starts with a study on crystalline silicon (c-Si), and in particular the influence of surface states on the KPFM measurement. The latter was performed in the dark and under light to extract the surface photovoltage (SPV). This study was completed by numerical simulations that allow to extract surface state densities. A second study was focused on nanowire PV devices. These were PIN radial junctions based on hydrogenated amorphous silicon deposited on highly doped c-Si nanowires. We have shown that on nanowire devices that are covered with ITO,SPV measurements could mirror the value of open-circuit voltage (Voc), while the same measurements performed on single nanowires without ITO top coverage are strongly affected by the shadowing of the AFM tip and by the surface states of the amorphous silicon layer. Finally, we were interested in passivating contacts for c-Si solar cells and analysed poly-Si/SiOx/c-Si structures. When the SiOx interlayer is absent, the KPFM scans exhibit very homogeneous surface potential while numerous areas (with diameter less than 1 micron) of lower surface potential are revealed, when the SiOx buffer layer is introduced. These results seem compatible with the presence of nanometric structural inhomogeneities (pinholes) in the SiOx layer that were revealed by other studies

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Della, Ciana Michele. "Morfologia e potenziale di contatto dell'interfaccia metallo/organico." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15799/.

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In questo lavoro di tesi si propone lo studio morfologico e del potenziale di contatto di un'interfaccia modello metallo/organico. Nello specifico si è analizzata l'interfaccia oro/sexitiofene composta da uno strato ultrasottile di oro (circa 0.3 nm) depositato su uno strato monomolecolare di sexitiofene (6T). Le molecole sono state depositate via Molecolar Beam Epitaxy (MBE) su un substrato conduttivo di indio stagno (ITO) con bassa rugosità superficiale (circa 4 Å). Nell’ambito di questo lavoro si è sviluppata anche una tecnica che permette di controllare il meccanismo di crescita del 6T ed ottenere uno strato monomolecolare che ricopre omogeneamente la superficie (ricopertura superficiale circa del 97%). L’oro è stato depositato sullo strato organico via Physical Vapor Deposition (PVD). Le tecniche di microscopia utilizzate sono l'Atomic Force Microscopy (AFM) e la Kelvin Probe Microscopy (KPM), rispettivamente per la misura della topografia e del potenziale di contatto. Dalle osservazioni sperimentali si deduce che la deposizione dell’oro non danneggia e non penetra lo strato di organico. Inaspettatamente è stato osservato un fenomeno di riorganizzazione superficiale dello strato di oro (de-wetting), attribuito a fenomeni legati all’energia superficiale delle interfacce. La riorganizzazione è tale da trasformare lo strato d’oro depositato sotto forma di un film continuo in un film granulare, composto da grani d’oro di raggio compreso nell’intervallo [8 – 10] nm. Il fenomeno di de-wetting dipende criticamente dallo spessore del film, nel nostro caso ultra-sottile e avviene in modo simile, ma non identico, sia sull’ITO sia sul 6T. L'analisi del potenziale di contatto ha mostrato le stesse relazioni di disuguaglianza attese dai valori riportati in letteratura. Fra i grani sopra il 6T e sopra l’ITO si osserva un contrasto nel potenziale di contatto, attribuito a una convoluzione laterale delle funzioni lavoro dei materiali.

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Spadafora, Evan. "Etude par microscopie à force atomique en mode non contact et microscopie à sonde de Kelvin, de matériaux modèles pour le photovoltaïque organique." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00647312.

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La nanostructure et les propriétés électroniques de matériaux modèles pour le photovoltaïque organique, ont été étudiées en utilisant la Microscopie à Force Atomique en mode non contact sous ultra-vide (NC-AFM) et la Microscopie à sonde de Kelvin (KPFM). En utilisant le mode modulation d'amplitude (AM-KPFM), le potentiel de surface photo- généré dans des mélanges donneur-accepteur présentant une ségrégation de phase optimale a pu être visualisé à l'échelle du nanomètre. Afin de préciser la nature des forces mises en jeu dans le processus d'imagerie KPFM, des oligomères π-conjugués auto-assemblés ont ensuite été étudiés. Une transition entre régimes à longue et à courte portée a ainsi été mise en évidence en combinant l'imagerie en haute résolution aux mesures de spectroscopie en distance. Ces mesures ont également démontré que l'influence des forces électrostatiques à courte portée peut être minimisée en travaillant au seuil du contraste de dissipation. Enfin cette procédure a été utilisée, en combinaison avec les mesures de spectroscopie de photoélectrons UV, pour analyser la fonction de sortie locale d'électrodes transparentes à base de nanotubes de carbone fonctionnalisés.

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Wu, Hao-Hsuan. "Angle-Resolved X-Ray Photoemission Spectroscopy of Self-Assembled Polymer Films on AlGaN/GaN Field Effect Transistors." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1305639462.

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Roche, Roland. "Plateforme multifonctionnelle de microscopies à sonde locale sous illumination." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4045/document.

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Afin de répondre à des besoins croissants en nano-caractérisation, nous avons développé une plateforme multifonctionnelle combinant des techniques de microscopie optique et de microscopies en champ proche.Au coeur de ce dispositif se trouve l'échantillon. Ceux optiquement semi-transparents en exploiteront au mieux la palette des techniques implémentées. Parmi eux des couches minces (100nm), nanostructurées, de matériaux organiques photovoltaïques.La plateforme permet d'utiliser différentes techniques de microscopies à sonde locale (AFM1, KPFM2, SNOM3, ...) couplées à un microscope optique inversé qui autorise illumination ou imagerie. Versatile, elle peut accueillir des portes-échantillons d'autres techniques développées ou présentes au laboratoire (en particulier les microscopies électroniques à projection, à transmission ou à balayage). Elle est également conçue pour faciliter l'intégration d'autres techniques.Outre le développement de la plateforme, ce manuscrit montre la part importante du travail effectuée pour mettre au point et exploiter une microscopie à sonde de Kelvin (KPFM) à haute résolution sous illumination.Des résultats obtenus sur des matériaux organiques photovoltaïques permettent notamment d'illustrer les excellentes performances de notre plateforme de nano-caractérisation et des techniques associées
To address the increasing demand on nanomaterials investigation, we developed a cross-characterization platform combining scanning probe microscopies (AFM 1, KPFM 2, SNOM 3, ...) and inverted optical microscopy. The inverted optical microscope, allowing both illumination and imaging, is augmented with near field microscopies such as cited above.The heart of our setup is the sample. Optically semi-transparent samples will best benefit the range of implemented complementary technics, among these samples, nanostructured organic photovoltaic thin (100nm) films. However, the flexible platform is thought to be adaptable to other samples and thus sample-holders used for other characterization techniques existing in the Institute, such as scanning or transmission electron or projection microscopies. The platform is also designed to simplify future extension to other experimental technics.Beyond the platform itself, the manuscript shows the important effort devoted to develop, and take benefit of, a Kelvin probe microscopy under illumination.Results obtained on organic photovoltaic materials demonstrate the possibilities of our original setup and prove its performance to be at state of the art

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Haußmann, Alexander. "Ferroelektrische Lithografie auf magnesiumdotierten Lithiumniobat-Einkristallen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-66638.

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Die Ferroelektrische Lithografie ist ein im letzten Jahrzehnt entwickeltes Verfahren zur gezielten Steuerung des Aufbaus von Nanostrukturen auf ferroelektrischen Oberflächen. Hierbei wird ausgenutzt, dass die unterschiedlich orientierte Spontanpolarisation des Materials in den einzelnen Domänen zu einer charakteristischen Variation der Oberflächenchemie führt. Die vorliegende Dissertation behandelt die Umsetzung dieses Ansatzes zur gezielten und steuerbaren Deposition von Nanostrukturen aus Edelmetallen oder organischen Molekülen. Diese Deposition erfolgte mittels einer nasschemischen Prozessierung unter UV-Beleuchtung auf magnesiumdotierten, einkristallinen Lithiumniobat-Substraten. Als typisches Ergebnis zeigte sich sowohl für in Wasser gelöste Silber-, Gold- und Platinsalze als auch für wässrige Lösungen des organischen Fluoreszenzfarbstoffs Rhodamin 6G eine bevorzugte Abscheidung des Materials an den 180°-Domänenwänden auf der Substratoberfläche. Dabei beginnt die Abscheidung in Form einzelner Nanopartikel innerhalb eines 150−500 nm breiten Streifens parallel zur Domänenwand. Bei fortgesetzter Beleuchtung erfolgt ein weiteres Wachstum der Kristallite bis zur ihrer gegenseitigen Berührung. Damit ermöglicht dieser Abscheideprozess den Aufbau organischer oder metallisch polykristalliner Nanodrähte mit Abmessungen um 100 nm in Breite und Höhe. Die Länge ist lediglich durch die Probenabmessungen begrenzt. Die so erzeugten Strukturen wurden im Rahmen der experimentellen Arbeiten topografisch, elektrisch und optisch charakterisiert. Am Beispiel einzeln kontaktierter Platindrähte konnte dabei deren annähernd ohmsches Leitfähigkeitsverhalten nachgewiesen werden. Zudem reagiert der Widerstand eines solchen Platin-Nanodrahtes sehr sensitiv auf Änderungen des umgebenden Gasmediums, was die Eignung solcher Strukturen für die Integration in künftige Sensorbauelemente unterstreicht. Weitergehende Untersuchungen beschäftigten sich mit der Klärung der Ursachen dieser sogenannten Domänenwanddekoration. Hierzu wurde die Lage der abgeschiedenen Strukturen mit dem zu Grunde liegenden Domänenmuster verglichen. Bis auf wenige Ausnahmen wurde dabei eine auf die Domänengrenze zentrierte, symmetrische Bedeckung nachgewiesen. Als Erklärungsansatz wird die Trennung der photoinduzierten Elektron-Loch-Paare durch das elektrostatische Feld der Polarisations- und Abschirmladungen diskutiert. Diese führt zur Ladungsträgerakkumulation und erhöhten chemischen Reaktivität an den Domänengrenzen
Ferroelectric lithography is a method for a controlled assembly of nanostructures on ferroelectric surfaces, which has has been established throughout the last decade. It exploits the characteristic variations in surface chemistry arising from the different orientations of the spontaneous polarisation within the separate domains. The scope of this thesis is the application of that approach for the directed and controlled deposition of nanostructures consisting of noble metals or organic molecules. For this deposition, a wet chemical processing under UV illumination was carried out on magnesium doped lithium niobate single crystals. As a typical result, the decoration of 180° domain walls was observed for aqueous solutions of silver, gold and platinum salts as well as for the dissolved organic fluorescent dye Rhodamine 6G. The deposition starts within a stripe of 150−500 nm in width parallel to the domain wall. Under continuing illumination, the crystallites grow further until they finally touch each other. Using this technique, organic or metallic polycrystalline nanowires with dimensions in the range of 100nm in width and height can be assembled. Their length is only limited by the sample size. These nanostructures were characterised in respect of their topographical, electrical and optical properties. In the case of contacted single platinum wires an electrical conduction was measured, which showed approximately ohmic behaviour. It was also shown that the resistance of such a platinum nanowire is very sensitive to changes in the surrounding gas medium. This emphasises the suitability of such structures for integration in future sensor devices. Further experiments were carried out to investigate the physical background of the observed domain wall decoration. For this, the positions of the deposited structures were compared with the underlying domain structure. Apart from few exceptions, a symmetric deposition centered at the domain wall was observed. As a starting point for explanation, the separation of electron-hole-pairs by the electrostatic field from polarisation and screening charges is discussed. This process leads to charge carrier accumulation at the domain boundaries, thus enhancing the local chemical reactivity

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Oger, Loïc. "Corrosion sous contrainte et fragilisation par l'hydrogène d'alliages d'aluminium de la série 7xxx (Al-Zn-Mg) : identification des paramètres microstructuraux critiques pilotant l'endommagement à l'échelle locale." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19559/19/OGER_Loic_1_sur_2.pdf.

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Dans un contexte normatif toujours plus sévère concernant les rejets automobiles polluants, la substitution des aciers par des alliages d’aluminium dans les structures des véhicules est en plein essor. Ce projet de thèse, qui s’inscrit dans un programme de développement de la société Constellium, cible plus précisément les alliages d’aluminium de la série 7xxx (Al-Zn-Mg) qui, malgré leurs propriétés mécaniques élevées, peuvent présenter une sensibilité à la corrosion sous contrainte (CSC) liée au phénomène de fragilisation par l’hydrogène (FPH). La compréhension des mécanismes mis en jeu dans ce type d’endommagement constitue donc une première étape vers une optimisation métallurgique en vue d’une industrialisation future de ces alliages dans le secteur automobile. La première partie de ces travaux est consacrée à l’étude de l’influence de l’état métallurgique de l’alliage 7046 sur son comportement en CSC et à l’identification des mécanismes de dégradation. Un lien direct a pu être mis en évidence entre l’abattement des propriétés mécaniques et les modes de rupture actifs et la quantité d’hydrogène dans l’alliage. Les deux modes d’endommagement observés, intergranulaire-fragile et transgranulaire-fragile, ont respectivement été attribués à un enrichissement en hydrogène aux joints de grains et au piégeage de l’hydrogène au niveau des précipités intragranulaires. Les interactions entre l’hydrogène et les précipités fins d’une part et les dislocations d’autre part, identifiés comme deux hétérogénéités microstructurales critiques vis-à-vis de la FPH, ont été étudiées à une échelle plus locale dans la seconde partie du travail de thèse. Les essais ont été réalisés sur des échantillons modèles, chargés en hydrogène en milieu H2SO4 sous polarisation cathodique et la profondeur de pénétration de l’hydrogène a été évaluée par SKPFM (Scanning Kelvin Probe Force Microscopy). L’ensemble des résultats obtenus met en évidence : 1/ un effet « barrière » des précipités fins et des dislocations sur la diffusion de l’hydrogène en relation avec un abattement des propriétés mécaniques moins important, 2/ un transport possible de l’hydrogène par les dislocations et 3/ l’efficacité du SKPFM pour déterminer précisément des coefficients de diffusion apparents de l’hydrogène. Ces résultats ouvrent ainsi de nouvelles pistes vers la compréhension des mécanismes de CSC dans les alliages Al-Zn-Mg.

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Schlaphof, Frank. "Kraftmikroskopische Untersuchungen dünner ferroelektrischer Filme." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1112181895822-13195.

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This thesis reports the inspection and manipulation of thin ferroelectric films of lead titanate (PbTiO3 : PTO), lead zirconium titanate (Pb(Zr0.25Ti0.75)O3 : PZT), and barium titanate (BaTiO3 : BTO) by means of scanning force microscopy - specifically Piezoresponse and Kelvin-Probe. The film thickness of the investigated samples ranged between 50nm and 800nm. This experimental work focussed on the following issues: native domain structures, creation of domains by short voltage pulses and area-switching with the force microscope, local qualitative and quantitative measurements of the ferroelectric hysteresis loops, and investigations at the interface between film and platinum-electrode in the PZT/Pt-System. Lamellar domain structures were visualized with high lateral resolution of 5nm on the surface of the PTO-samples, whereas the PZT- and BTO-samples showed prepolarisation and no domains. In the switching experiments a pronounced thickness dependence was found and partly a good agreement to macroscopic measurements. For BTO-films of 50nm and 125nm thickness no stable switching of polarisation could be observed. Using appropriate preparation methods it was possible to provide evidence of a 200nm thick interface layer with reduced polarisation above the electrode in the PZT/Pt-system
Gegenstand dieser Arbeit ist die Untersuchung dünner ferroelektrischer Schichten von Bleititanat (PbTiO3 : PTO), Bleizirkoniumtitanat (Pb(Zr0.25Ti0.75)O3 : PZT) und Bariumtitanat (BaTiO3 : BTO) und deren Manipulation auf der sub-µm-Skalamittels Rasterkraftmikroskopie. Die Dicke der Schichten lag im Bereich von 50nm bis 800nm. Zum Einsatz kamen die Meßmodi Piezoresponse und Kelvin-Sonde. Die experimentelle Arbeit erstreckte sich über die Abbildung von Domänenstrukturen, die Erzeugung von Domänen durch kurze Spannungspulse und flächiges Umschalten mit dem Kraftmikroskop, lokale qualitative und quantitative Messungen der ferroelektrischen Hysterese, sowie Untersuchungen an der Grenzschicht zwischen Film und Platin-Elektrode am PZT/Pt-System. Lamellenartige Domänenstrukturen konnten mit hoher lateraler Auflösung von 5nm auf der Oberfläche von PTO abgebildet werden. Die PZT- und BTO-Proben waren vorpolarisiert und es ließen sich keine Domänen nachweisen. Bei den Schaltversuchen wurde eine ausgeprägte Schichtdickenabhängigkeit der Koerzitivfeldstärken und teilweise gute Übereinstimmung mit makroskopischen Messungen gefunden. Für dünne BTO-Schichten von 50nm und 125nm Dicke konnte kein stabiles Umschalten der Polarisation gezeigt werden. Mittels geeigneter Präparation der PZT/Pt-Grenzschicht konnte durch direkte Messung eine Schicht von 200nm Dicke mit verminderter Polarisation oberhalb der Elektrode nachgewiesen werden

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Luchkin, Sergey Yurevich. "Local probing of Li+ diffusion and concentration in Li-ion battery materials by scanning probe microscopy." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14825.

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Doutoramento em Ciência e Engenharia de Materiais
This thesis presents the results of Scanning Probe Microscopy (SPM) study of Li-ion battery active materials. The measurements have been performed on LiMn2O4 cathodes and graphite anodes extracted from commercial Li batteries at different states of charge and health. The study has been focused on measurements of Li spatial distribution and transport properties in the active electrode materials. Special attention has been paid to influence of fatigue caused by high C rate cycling on Li spatial distribution and local diffusion coefficient. Electrochemical Strain Microscopy (ESM) has been used to access Li transport properties at the nanoscale in LiMn2O4 cathodes. Kelvin Probe Force Microscopy (KPFM) has been used to examine Li spatial distribution in graphite anodes. ESM has been implemented and used in a single frequency mode out of the contact resonance for the first time. Signal-to-noise ratio analysis has been performed for a number of single- and multi-frequency modes used in ESM. The analysis allowed to establish criteria for a proper cantilever choice and an experimental setup for the optimized detection of surface displacements via lock-in amplifier. Transport properties of Li+ mobile ions in fresh and fatigued LiMn2O4 battery cathodes have been studied at the nanoscale via ESM using time-and voltage spectroscopies. Both Vegard and non-Vegard contributions to ESM signal have been identified in electrochemical hysteresis loops obtained on the fresh and fatigued samples. In fresh cathodes the Vegard contribution dominates the signal, while in fatigued samples different shape of hysteresis loops indicates additional contributions. Non-uniform spatial distribution of the electrochemical loop opening in LiMn2O4 particles studied in the fatigued samples indicates stronger variation of Li diffusion coefficients in fatigued samples’ as compared to the fresh one. Time spectroscopy measurements have revealed suppressed local Li diffusivity in fatigued samples by more than two orders of magnitude as compared to the fresh one. We attributed such reduction of the diffusion coefficient to the accumulation of point defects induced by high C-rate cycling and accompanied structural instability. This mechanism can be specifically important for high C-rate cycling. Li spatial distribution in fresh and fatigued graphite cathodes has been accessed via KPFM using a 2-pass amplitude modulation mode. Core-shell and mosaic surface potential structures have been observed on the fatigued and fresh anodes, respectively. The observed surface potential distributions have been attributed to the apparent Li concentration profiles in graphite. The core-shell potential distribution has been attributed to the remnant Li ions stacked in graphite particles causing irreversible capacity loss. The mosaic potential distribution has been attributed to inactive Li inside graphite at the starting stage of cycling. The results corroborate the “radial” model used to explain the specific capacity fading mechanism at high C rate cycling in Li-ion batteries.
Esta tese apresenta os resultados do estudo de Scanning Probe Microscopia (SPM) de materiais de baterias de ions de litio. As medidas foram executadas na cátodos de LiMn2O4 e ânodos de grafite extraidos de bateriais de litio comerciais em diferentes estados de carga e fadiga. O estudo concentrou-se na medição da distribuição de Li e propriedades de transporte dos materiais de eletrodo ativo. Especial atencao tem sido dada a influencia do ciclo de fadiga da elevada taxa C na distribuicao especial dos ions de Li e coeficiente de difusao. Microscopia de tensão eletroquímica (ESM) tem sido usada para acessar Li transporte propriedades em nanoescala em cátodos de LiMn2O4. Microscopia de força de sonda Kelvin (KPFM) tem sido usada para acessar a distribuição espacial de Li em anodos de grafite. ESM foi implementada e usada em um modo de única freqüência de ressonância o contato pela primeira vez. Análise de relação sinal-ruído foi feito para um número de monomodo e multimodo usados no ESM. A análise permite estabelecer critérios para um cantilever e uma instalação experimental para a detecção mais sensível de deslocamentos superficiais. Propriedades da mobilidade dos ions de lition em catodos de bateria LiMn2O4 frescos e fatigados foram estudados em nanoescala via ESM, espectroscopia de tempo e espectroscopia de tensão de transporte. Contribuições como sinal Vegard e non-Vegard ESM foram identificadas em ciclos de histerese eletroquímica obtidos em amostras frescas e fatigadas. Em cátodos frescos o sinal Vegard dominante, enquanto em amostras envelhecidas, a diferente ciclo de histerese indica contribuições adicionais. Distribuição espacial não-uniforme do ciclo aberto eletroquímico em partículas de LiMn2O4 foram estudadas nas amostras fatigadas indicando mais forte variação do coeficiente de difusão de Li das amostras fatigadas em microescala em comparação com a outra amostra. Medições de espectroscopia de tempo revelaram a ausencia de difusidade local em amostras fatigadas por mais de duas ordens de magnitude em comparação com a outra. Atribui-se tal redução do coeficiente de difusão o acúmulo de defeitos de ponto induzida pelo Ciclo de elevada taxa C e acompanhadas de instabilidade estrutural. Este mecanismo pode ser especialmente importante para ciclo de elevada taxa C. Distribuição espacial de Li em cátodos amostras fresca e fatigada grafite foi analisaa via KPFM no modo de modulação de amplitude 2-pass. Estruturas de superfícies potenciais core-shell e mosaico têm sido observadas em ânodos fatigados e frescos, respectivamente. As distribuições de superfícies potenciais observadas foram atribuídas para os perfis de concentração Li aparentes em grafite. Distribuição potencial core-shell tem sido atribuída para o ions remanescentes de Li empilhados em partículas de grafite, causando perda irreversível de capacidade. A distribuição de potencial de mosaico tem sido atribuída a Li inativo dentro do grafite na fase inicial do ciclo. Os resultados corroboram o modelo "radial" usado para explicar o mecanismo de desvanecimento de capacidade específica a alta taxa de C em baterias de íon-lítio.

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Aghamohammadi, Mahdieh. "Nanoscale investigation and control of the interfacial properties of organic solar cells and organic thin-film transistors." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/392722.

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Las propiedades de las películas de semiconductores orgánicas y, en particular, de las interfases involucradas, son uno de los aspectos más prominentes en relación con la eficiencia de los dispositivos orgánicos. La interfase formada entre dos materiales orgánicos puede influenciar las propiedades electrónicas y ópticas de los dispositivos de diferentes manteras: por los mecanismos de crecimiento, la morfología, la densidad de defectos y la estructura electrónica. El impacto de la orientación molecular en interfases de materiales orgánicos es una de las cuestiones menos entendidas y menos investigadas en relación con la eficiencia de células solares orgánicas. Mediante el uso de microscopia de sonda cercana (SPM) y fotoluminiscencia, se ha demostrado en esta tesis una correlación clara entre la orientación molecular en la interfase de DIP (donor)/PTCDI-C8 (aceptor) y la formación de un estado de transferencia de carga para aquellas heteroestructuras en las que el solape de los orbitales p en moléculas adyacentes es favorecido. Otro tipo de interfase de materiales orgánicos de gran relevancia se encuentra en los transistores orgánicos de película delgada (TFTs), en el que el dieléctrico es funcionalizado con películas orgánicas autoensambladas (SAMs). El uso de SAMs es una tecnología muy prometedora en la manufacturación de transistores orgánicos para conseguir voltajes de operación deseados dado que el voltaje umbral de operación puede ser modulado mediante la elección de las SAMs. El origen físico de este fenómeno ha sido muy debatido en la literatura y permanece una cuestión abierta. Microscopia de sonda Kelvin ha sido empleada como herramienta para explorar las propiedades electrónicas de la interfase entre DNTT (semiconductor orgánico) y dos SAMs con cadenas alquílica terminadas en grupos metil o metil fluorinados. Dicho estudio en correlación con la operación de los TFTs con DNTT ha revelado que el voltaje umbral depende de la capacitancia del dieléctrico solamente para la SAM fluorinada y se ha determinado que se debe a la interacción electrónica en la interfase entre DNTT y los grupos F de la SAM. En conjunto, los estudios realizados en esta tesis combinan una serie de métodos sistemáticos y técnicas complementarias que han permitido abordar el efecto de procesos electrónicos en interfases de relevancia en células solares y TFTs. Los resultados de esta tesis ponen de manifiesto la importancia del control de las propiedades estructurales y electrónicas de las interfases de materiales orgánicos como paso necesario para mejorar la eficiencia de dispositivos.
Thin-film and interface properties of organic semiconductors are among the most prominent aspects with regard to the overall performance of organic electronic devices. The interface formed between two organic materials can influence the electronic and optical properties of organic electronic devices by determining the growth mechanisms, morphology, defect density and the electronic interface structures of organic films. The impact of the relative molecular orientation at the organic/organic interface on the performance of organic solar cells is one of the less understood factors and thus, it represents an outstanding opportunity for research and technologies based on the control of the local molecular ordering of the organic molecules in donor/acceptor organic photovoltaics. Using state-of-the-art scanning probe microscopy techniques and photoluminescence studies a clear link between the relative molecular orientation of the DIP (donor)/PTCDI-C8 (acceptor) heterostructures and an emissive charge transfer state is demonstrated, which is ultimately associated with an efficient π-orbital overlap at the interface. Another extremely interesting organic/organic interface is the one found in organic thinfilm transistors (TFTs), where the gate dielectric contains organic species such as selfassembled monolayers (SAMs). The use of SAMs opens an appealing path of research in manufacturing TFTs with the desired operating voltages, due to the observation that the threshold voltage can be modulated using different SAMs. Revealing the underlying mechanisms of this phenomenon, which is known as threshold-voltage shift, signifies a considerable challenge. Kelvin probe force microscopy (KPFM) was used as a powerful tool to explore at the nanoscale the electronic properties at the interface between DNTT and two different SAMs namely an alkly- and a fluoroalkylphosphonic acid SAM. A systematic series of KPFM investigations combined with the analysis of the transistor parameters reveals gate-oxide capacitance-dependent threshold-voltage shift as a result of interface electronic interactions at the DNTT/fluoroalkyl SAM interface. On the contrary, the DNTT transistors with the alkyl SAMs exhibit a small capacitanceindependent threshold-voltage shift, associated with the intrinsic dipole-induced electrostatic potential of the SAM. Together, the studies carried out in this thesis represent innovative approaches utilizing controlled organic semiconductor processing methods and complementary techniques, which enabled us to achieve a better understanding of different electronic processes at the interfaces involved in organic solar cells and organic thin-film transistors. This thesis emphasizes the relevance of achieving controlled interface architectures with exciting potential for future interface engineering in organic electronic devices.

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Fuchs, Franz. "Systèmes modèles donneur accepteur pour le photovoltaïque organique étudiés par microscopie à sonde locale." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY036/document.

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Pour cette thèse, des systèmes donneur-accepteur (DA) modèles pour le photovoltaïque organique ont été étudiés par microscopie à force atomique en mode non contact (nc-AFM) et microscopie à sonde de Kelvin (KPFM). Ces systèmes DA présentent une structure et des propriétés électroniques mieux contrôlées que dans la plupart des hétérojonctions DA en volume.Afin, d'étudier les propriétés optoélectroniques d'architectures DA présentant une séparation de phase à l'échelle de la dizaine de nanomètres, il est indispensable d'optimiser la résolution des modes nc-AFM/KPFM. Dans ce travail, l'influence du régime d'interaction pointe-surface sur les mesures a été étudiée dans le cas d'auto-assemblages de P3DDT sur substrat HOPG. Nous avons ainsi démontré que l'imagerie dans le régime d'interaction à courte portée améliore non seulement la résolution latérale, mais permet également de réaliser des mesures de hauteur plus réalistes.Ensuite, un système DA à base de FG1:[70]PCBM a été étudié. Pour ce mélange DA, la nanostructure et l'échelle de la séparation de phase peuvent être ajustées grâce aux propriétés cristal liquide du composé donneur FG1. Les potentiels mesurés dans le noir sont consistants avec la morphologie attendue en surface et en volume. La relation entre le photo-potentiel de surface (SPV) et le régime d'interaction pointe-surface a pu être précisément analysée. Une résolution optimale est obtenue dans les images de SPV en travaillant près du seuil de dissipation.Enfin, une nouvelle génération de diades comprenant des groupements donneur et accepteur a été étudiée. La nature de l'auto-assemblage sur HOPG a été établie sur la base d'études comparatives de microscopie à effet tunnel et de nc-AFM, avec le support de simulations en mécanique et dynamique moléculaire. Les mesures de photo-potentiel de surface ont ensuite permis de démontrer qu'il était possible d'étudier les mécanismes de photo-génération des porteurs jusqu'à l'échelle de la mono-couche moléculaire
During this thesis, model donor-acceptor (DA) systems for organic photovoltaics have been studied by non-contact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). To enhance the understanding of the optoelectronic processes on the nanoscale, DA systems with better defined structural and electronic properties than the one of most bulk heterojunction blends (BHJ), have been studied.With DA phase-separations of below 10nm in organic photovoltaic systems, the highest possible resolution has to be achieved by KPFM to investigate optoelectronic processes. It has been shown that nc-AFM/KPFM measurements in the regime of short range (SR) forces can increase imaging resolution. In preparation of such investigations, the influence of the interaction regime on the topographic measurement via KPFM has been studied for a self-assembly of P3DDT on HOPG. It is demonstrated that imaging in the SR-regime not only increases the lateral resolution, but also assures a correct topographic height values.In a next step, DA blends of FG1:[70]PCMB have been studied by KPFM. For these BHJs, the structure and the scale of the DA phase-separation can be tuned via the liquid crystal behavior of the donor FG1. The in dark potential contrasts are consistent with surface and bulk morphology. The relationship between the surface photovoltage (SPV) and the tip-sample interaction regime has been analyzed. An optimal resolution for SPV imaging is obtained when measuring next to the onset of dissipation.Finally, a new generation of DA dyad with donor and acceptor moieties has been studied. Its self-assembly on HOPG has been determined via a comparative study by scanning tunneling microscopy and nc-AFM plus molecular mechanics and dynamics simulations. By KPFM the charge carrier generation and collection has been analyzed down to the level of a single molecular layer. A clear relationship between the dyads' molecular assembly and their photovoltaic properties can be established

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Alchaar, Mohanad. "Confinement et transfert de charges dans les systèmes îlots Au/AlN et îlots graphène/SiC." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30287.

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L'étude du confinement et du transfert de charges au sein de nano-objets métalliques déposés sur un substrat isolant constitue un enjeu majeur d'un point de vue scientifique et technologique. Un tel système pourrait servir de réservoir d'électrons en vue d'étudier le transfert dans un fil moléculaire. Durant cette thèse, la technique utilisée est la microscopie à force atomique en mode non contact (NC-AFM) fonctionnant sous ultra vide (UHV) et couplée à la sonde de Kelvin (KPFM), permettant la mesure et le transfert des charges électriques. Le substrat isolant utilisé dans cette thèse est le nitrure d'aluminium AlN(0001) élaboré par épitaxie par jets moléculaires (EJM). Une première étude de croissance de 4 métaux (Mg, In, Ag et Au) par EJM a mis en évidence l'importance primordiale de la surface AlN(0001) sur les modes de croissance. Cette étude a permis de montrer que seul l'or déposé sur la surface AlN(0001) reconstruite (2×2)-Nad donnait lieu à une croissance bidimensionnelle (2D) avec formation de nano-îlots de une monocouche d'épaisseur. L'analyse d'images NC-AFM à résolution atomique obtenues à 5K, couplée à des calculs DFT montre que la stabilisation des nano-îlots d'or est due à la formation de liaison chimique entre l'or et la surface AlN(0001). Ces nano-îlots d'or 2D sur AlN(0001) ont pu être chargé positivement ou négativement lors d'expériences NC-AFM : la signature caractéristique de la charge est observée lors de spectroscopies DELTA f(V), avec le décalage du potentiel CPD lié à la charge injectée. Le suivi temporel du potentiel Kelvin sur un îlot chargé permet de mesurer un temps de décroissance de plusieurs jours, signe que le substrat AlN est un très bon isolant. Afin de comprendre le mécanisme de charge de ces îlots métalliques par NC-AFM, ces expériences de charges ont été reproduites sur des nanocristaux d'or de 20 nm d'épaisseur déposés sur une couche isolante de SiO2 thermique. Un modèle analytique couplé à des simulations numériques a permis de montrer que l'injection de charge se fait par émission de champ entre la pointe et l'îlot métallique. Ces calculs montrent qu'il est possible de contrôler à l'électron prêt la quantité de charge injectée dans un îlot métallique. La dernière partie de cette thèse est consacrée à la mesure par NC-AFM/KPFM de la hauteur de trois types de graphène (ZLG, EMLG et QFMLG) et deux îlots de graphène. L'étude est faite sur deux types d'échantillons : des nano-îlots de graphène élaborés par CVD sur un substrat de 6H-SiC(0001) et des couches de graphène obtenues par sublimation à haute température de 6H-SiC(0001), avec un taux de couverture d'environ une demi monocouche. L'analyse des images NC-AFM a permis de déterminer la hauteur de la couche tampon (ZLG) égale à 2.62 Å, de la couche de graphène épitaxiée sur la couche tampon (EMLG), égale à 4.09 Å, ainsi que d'une bicouche de graphène égale à 6.86 Å. La hauteur d'un îlot de graphène sur SiC est de 6.28 ± 0.52 Å et un îlot de graphène sur ZLG est caractérisé par une hauteur de 3.69 ± 0.11 Å
The study of confinement and charge transfer within metallic nano-objects deposited on an insulating substrate is a major challenge from a scientific and technological viewpoint. Such a system could serve as a reservoir of electrons to study the transfer in a molecular wire. During this thesis, the technique used is non-contact atomic force microscopy (NC-AFM) connected under ultra-high vacuum (UHV) and coupled to the Kelvin probe (KPFM), allowing the measurement and transfer of electric charges. The insulating substrate used in this thesis is aluminum nitride AlN (0001) prepared by molecular beam epitaxy (MBE). A first growth study of four metals (Mg, In, Ag and Au) by MBE has highlighted the fundamental importance of the AIN (0001) surface on the growth modes. This study showed that only the gold deposited on the AlN (0001) (2×2)-Nad reconstructed surface gave rise to two-dimensional (2D) growth with the formation of nano-islands a thick monolayer. The analysis of NC-AFM images at atomic resolution obtained at 5K, coupled with DFT calculations, shows that the stabilization of the gold nano-islands are due to the formation of a chemical bond between the gold and the AlN surface (0001). These 2D gold nano-islands on AlN (0001) could have been positively or negatively charged during NC-AFM experiments: the characteristic signature of the charge is observed during DELTA f(V) spectroscopies, with the offset of the CPD potential linked to the injected load. Time tracking of the Kelvin potential on a charged island makes it possible to measure a decay time of several days, a sign that the AlN substrate is a very good insulator. In order to understand the charge mechanism of these metallic islands by NC-AFM, these charge experiments were reproduced on 20 nm thick gold nanocrystals deposited on an insulating layer of thermal SiO2. An analytical model coupled with numerical simulations made it possible to show that the charge injection takes place by field emission between the tip and the metallic island. These calculations show that it is possible to control with ready electron the amount of charge injected into a metallic island. The last part of this thesis is devoted to the measurement by NC-AFM / KPFM of the height of three types of graphene (ZLG, EMLG and QFMLG) and two islands of graphene. The study is carried out on two types of samples: nano-islands of graphene grown by CVD on a 6H-SiC(0001) substrate and graphene layers obtained by high temperature sublimation of 6H-SiC(0001), with a half monolayer coverage rate. Analysis of the NC-AFM images made it possible to determine the height of the buffer layer (ZLG) equal to 2.62 Å, of the epitaxial layer graphene on the buffer layer (EMLG), equal to 4.09 Å, as well as a bilayer graphene equal to 6.86 Å. The height of an island of graphene on SiC is 6.28 ± 0.52 Å and an island of graphene on ZLG is characterized by a height of 3.69 ± 0.11 Å

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35

Doutt, Daniel R. "THE ROLE OF NATIVE POINT DEFECTS AND SURFACE CHEMICAL REACTIONS IN THE FORMATION OF SCHOTTKY BARRIERS AND HIGH N-TYPE DOPING IN ZINC OXIDE." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366199639.

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36

Schlaphof, Frank. "Kraftmikroskopische Untersuchungen dünner ferroelektrischer Filme." Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24474.

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This thesis reports the inspection and manipulation of thin ferroelectric films of lead titanate (PbTiO3 : PTO), lead zirconium titanate (Pb(Zr0.25Ti0.75)O3 : PZT), and barium titanate (BaTiO3 : BTO) by means of scanning force microscopy - specifically Piezoresponse and Kelvin-Probe. The film thickness of the investigated samples ranged between 50nm and 800nm. This experimental work focussed on the following issues: native domain structures, creation of domains by short voltage pulses and area-switching with the force microscope, local qualitative and quantitative measurements of the ferroelectric hysteresis loops, and investigations at the interface between film and platinum-electrode in the PZT/Pt-System. Lamellar domain structures were visualized with high lateral resolution of 5nm on the surface of the PTO-samples, whereas the PZT- and BTO-samples showed prepolarisation and no domains. In the switching experiments a pronounced thickness dependence was found and partly a good agreement to macroscopic measurements. For BTO-films of 50nm and 125nm thickness no stable switching of polarisation could be observed. Using appropriate preparation methods it was possible to provide evidence of a 200nm thick interface layer with reduced polarisation above the electrode in the PZT/Pt-system.
Gegenstand dieser Arbeit ist die Untersuchung dünner ferroelektrischer Schichten von Bleititanat (PbTiO3 : PTO), Bleizirkoniumtitanat (Pb(Zr0.25Ti0.75)O3 : PZT) und Bariumtitanat (BaTiO3 : BTO) und deren Manipulation auf der sub-µm-Skalamittels Rasterkraftmikroskopie. Die Dicke der Schichten lag im Bereich von 50nm bis 800nm. Zum Einsatz kamen die Meßmodi Piezoresponse und Kelvin-Sonde. Die experimentelle Arbeit erstreckte sich über die Abbildung von Domänenstrukturen, die Erzeugung von Domänen durch kurze Spannungspulse und flächiges Umschalten mit dem Kraftmikroskop, lokale qualitative und quantitative Messungen der ferroelektrischen Hysterese, sowie Untersuchungen an der Grenzschicht zwischen Film und Platin-Elektrode am PZT/Pt-System. Lamellenartige Domänenstrukturen konnten mit hoher lateraler Auflösung von 5nm auf der Oberfläche von PTO abgebildet werden. Die PZT- und BTO-Proben waren vorpolarisiert und es ließen sich keine Domänen nachweisen. Bei den Schaltversuchen wurde eine ausgeprägte Schichtdickenabhängigkeit der Koerzitivfeldstärken und teilweise gute Übereinstimmung mit makroskopischen Messungen gefunden. Für dünne BTO-Schichten von 50nm und 125nm Dicke konnte kein stabiles Umschalten der Polarisation gezeigt werden. Mittels geeigneter Präparation der PZT/Pt-Grenzschicht konnte durch direkte Messung eine Schicht von 200nm Dicke mit verminderter Polarisation oberhalb der Elektrode nachgewiesen werden.

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37

Hoff, Brice. "Nanostructuration et caractérisation en ultravide de dépôts de molécules sur surfaces isolantes par microscopie à force atomique en mode non-contact et sonde de Kelvin." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4078/document.

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Grâce à des expériences en ultra-vide avec un AFM en mode non-contact (nc-AFM) et une nano-sonde de Kelvin (KPFM), nous avons pu précisément caractériser plusieurs dépôts de molécules sur différentes surfaces isolantes, dont la surface (001) de monocristaux de NaCl dopés par des ions Cd2+, appelée la surface de Suzuki. Cette surface est nanostructurée de façon à ce que deux régions très distinctes coexistent : des régions de NaCl pures et des régions de Suzuki qui recouvrent partiellement la surface (001) du cristal. Nous montrons que la surface de Suzuki peut être utilisée comme surface nanostructurée dans le but de confiner l'adsorption de nano-objets tels que des molécules organiques ou inorganiques. Après déposition de différentes molécules pentahélicènes fonctionalisées, une large partie de celles-ci reste préférentiellement adsorbée dans les régions de Suzuki. Suite aux observations nc-AFM et KPFM un modèle sera présenté sur les mécanismes d'adsorption et désorption de ces hélicènes, accompagné d'une étude étonnante sur des ilots de molécules fullerènes C60 déposés sur plusieurs surfaces isolantes, et la manipulation de charges dans ces ilots
Thanks to ultra high vacuum experiments using non-contact AFM and Kelvin probe force microscopy (KPFM), we have been able to characterize precisely several depositions of molecules on different surfaces, including the (001) surface of a Cd2+ doped NaCl single crystal called the Suzuki surface. This surface is nanostructured such as two different regions coexist : pure NaCl regions and Suzuki regions covering partially the (001) surface. We show that the Suzuki surface can be used as a nanotemplate in order to confine the adsorption of nano-objects such as organic or inorganic molecules. After deposition of different functionalised pentahelicenes molecules, a large part of those stay preferentially adsorbed on Suzuki regions. Following the nc-AFM and KPFM observations a model will be presented on the mechanism of adsorption and desorption of those helicenes, accompanied with a astonishing study about fullerenes C60 molecules deposed on several surfaces, and the charge manipulation in these islands

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38

Teich, Sebastian. "Oberflächenphotospannung an dünnen organischen Schichten auf Metallsubstraten." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1239005029403-92681.

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Gegenstand dieser Arbeit ist die Untersuchung der Ober?ächen- bzw. Grenz?ächenphotospannung (SPV) an dünnen organischen Schichten auf Metallsubstraten. Besonderes Augenmerk gilt dabei dem System dünner Schichten von 3,4,9,10-Perylen- Tetracarbonsäure-Di-Anhydrid (PTCDA) auf einem Au(110)-Kristall. Für diese Untersuchungen wurde eine phasensensitive Methode auf der Basis der Photoelektronenspektroskopie (PES) mit zusätzlicher modulierter Lichteinstrahlung entwickelt, die es erlaubt, lichtinduzierte Verschiebungen des Ober?ächenpotentials mit einer Au?ösung ? 1mV zu detektieren. Diese modulierte Photoelektronenspektroskopie wird ausführlich vorgestellt. Eine makroskopische Kelvin-Sonde und die Kelvin-Sonden-Rasterkraftmikroskopie (KPFM) werden als weitere Möglichkeiten zur Bestimmung des Ober?ächenpotentials vorgestellt. Die Photospannung wird mit diesen Methoden in Bezug auf drei Parameter untersucht: Da die Barriere an der Grenz?äche, welche für die Ausbildung der Photospannung ursächlich ist, durch die Photospannung reduziert wird, geben Messungen der SPV in Abhängigkeit von der eingestrahlten Lichtleistung Informationen über die energetische Struktur der Grenz?äche, speziell über die Höhe der Barriere. Mit den ebenfalls aus diesen Methoden gewonnen Informationen über die Austrittsarbeit und Ionisationsenergie von PTCDA lässt sich ein Bandschema des Systems Au/PTCDA entwickeln. Die wellenlängenabhängigen Messungen zeigen, dass Exzitonen in verschiedenen Zuständen erzeugt werden. Diese werden mit unterschiedlichen Photonenenergien angeregt und besitzen unterschiedliche Di?usionslängen. Da die Exzitonen zum Dissoziieren an die Grenz?äche di?undieren müssen, tragen die unterschiedlichen Exzitonenzust ände mit unterschiedlichem Anteil zur Photospannung bei. Die Untersuchungen der Entstehungs- und Zerfallszeit zeigen, dass sich die Photospannung sehr schnell nach Lichteinschaltung aufbaut. Der Abbau der Photospannung nach Lichtabschaltung erfolgt vergleichsweise langsam. Dies bedeutet, dass die Ladungsträger, die nach der Ladungsträgertrennung in der organischen Schicht zur ückbleiben, in Fallenzuständen gebunden sind, aus denen sie thermisch aktiviert werden müssen. In einem separaten Abschnitt werden die Entwicklung sowie Messergebnisse eines Stimmgabel-Rasterkraftmikroskops (AFM) vorgestellt. Dieses ermöglicht die hochau ?ösende topographische Abbildung der Ober?äche mit einer vertikalen Sensitivität im Ångström-Bereich. Das Ziel, mit diesem Gerät KPFM zu betreiben, konnte beim Einsatz an Luft nicht verwirklicht werden
Subject of this work is the investigation of surface and interface photovoltage (SPV) of thin organic films on metal substrates. Special attention is focused on the system of thin layers of 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) on an Au(110) crystal. For this investigation a novel phase sensitive method was developed based on photoelectron spectroscopy (PES) under additional modulated illumination. It provides the possibility to detect light induced changes in the surface potential with a resolution of about 1mV. This modulated photoelectron spectroscopy is described in detail. Macroscopic Kelvin probe and Kelvin probe force microscopy (KPFM) are presented as further possibilities to measure the surface potential. The photovoltage is investigated by these techniques regarding three parameters: Due to the fact that the barrier at the interface is responsible for the formation of the photovoltage and that the height of this barrier is reduced by the photovoltage, the measurement of the dependence of the SPV on the intensity of the incident light provides information about the energetic structure of the interface. Together with the values of the work function and the ionisation energy of PTCDA, also gained with this methods, a band diagram of the interface can be developed. The wavelength dependent measurements show that excitons can be generated in multiple states. They are excited at different photon energies and have different diffusion lengths. The excitons have to diffuse to the interface to dissociate. Therefore the different excitation states contribute to SPV with different amounts. The investigations upon the generation and decay of the photovoltage shows that the SPV signal appears immediately after switching on the illumination. The decay of the photovoltage after switching off the light is much slower. This implies that the charge carriers are trapped as they remain in the organic film after charge separation at the interface. They have to be thermally activated from this traps. In an extra chapter the development and measurement results of a tuning fork scanning force microscope (AFM) are described. This AFM features high resolution topography images with a vertical sensitivity in the range of single angstroms

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39

Kovařík, Martin. "Charakterizace elektronických vlastností nanodrátů pro elektrochemii." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402570.

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Elektrochemické metody nacházejí využití v mnoha aplikacích (např. senzorice, skladování el. energie nebo katalýze). Jejich nespornou výhodou je nízká finanční náročnost na přístrojové vybavení. Abychom lépe porozuměli procesům probíhajícím na elektrodách, je dobré znát elektronickou pásovou strukturu materiálu elektrody. Úkolem této práce je vyhodnotit výstupní práci a pozici hrany valenčního pásu nových materiálů pro elektrody, konkrétně cínem dopovaného oxidu india pokrytého nanotrubicemi sulfidu wolframičitého. Ultrafialová fotoelektronová spektroskopie a Kelvinova silová mikroskopie jsou metody použité pro tuto analýzu. Zvláštní důraz je kladen na přípravu vzorků elektrod pro měření, aby nedošlo k nesprávné interpretaci výsledků vlivem vnějších efektů jako je např. kontaminace nebo modifikace povrchu.

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40

Lin, Chung-Han. "The Effects of Thermal, Strain, and Neutron Irradiation on Defect Formation in AlGaN/GaN High Electron Mobility Transistors and GaN Schottky Diodes." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1371466261.

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41

Chiesa, Marco. "Scanning Kelvin probe microscopy of organic devices." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613074.

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42

Teich, Sebastian. "Oberflächenphotospannung an dünnen organischen Schichten auf Metallsubstraten." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23728.

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Gegenstand dieser Arbeit ist die Untersuchung der Ober?ächen- bzw. Grenz?ächenphotospannung (SPV) an dünnen organischen Schichten auf Metallsubstraten. Besonderes Augenmerk gilt dabei dem System dünner Schichten von 3,4,9,10-Perylen- Tetracarbonsäure-Di-Anhydrid (PTCDA) auf einem Au(110)-Kristall. Für diese Untersuchungen wurde eine phasensensitive Methode auf der Basis der Photoelektronenspektroskopie (PES) mit zusätzlicher modulierter Lichteinstrahlung entwickelt, die es erlaubt, lichtinduzierte Verschiebungen des Ober?ächenpotentials mit einer Au?ösung ? 1mV zu detektieren. Diese modulierte Photoelektronenspektroskopie wird ausführlich vorgestellt. Eine makroskopische Kelvin-Sonde und die Kelvin-Sonden-Rasterkraftmikroskopie (KPFM) werden als weitere Möglichkeiten zur Bestimmung des Ober?ächenpotentials vorgestellt. Die Photospannung wird mit diesen Methoden in Bezug auf drei Parameter untersucht: Da die Barriere an der Grenz?äche, welche für die Ausbildung der Photospannung ursächlich ist, durch die Photospannung reduziert wird, geben Messungen der SPV in Abhängigkeit von der eingestrahlten Lichtleistung Informationen über die energetische Struktur der Grenz?äche, speziell über die Höhe der Barriere. Mit den ebenfalls aus diesen Methoden gewonnen Informationen über die Austrittsarbeit und Ionisationsenergie von PTCDA lässt sich ein Bandschema des Systems Au/PTCDA entwickeln. Die wellenlängenabhängigen Messungen zeigen, dass Exzitonen in verschiedenen Zuständen erzeugt werden. Diese werden mit unterschiedlichen Photonenenergien angeregt und besitzen unterschiedliche Di?usionslängen. Da die Exzitonen zum Dissoziieren an die Grenz?äche di?undieren müssen, tragen die unterschiedlichen Exzitonenzust ände mit unterschiedlichem Anteil zur Photospannung bei. Die Untersuchungen der Entstehungs- und Zerfallszeit zeigen, dass sich die Photospannung sehr schnell nach Lichteinschaltung aufbaut. Der Abbau der Photospannung nach Lichtabschaltung erfolgt vergleichsweise langsam. Dies bedeutet, dass die Ladungsträger, die nach der Ladungsträgertrennung in der organischen Schicht zur ückbleiben, in Fallenzuständen gebunden sind, aus denen sie thermisch aktiviert werden müssen. In einem separaten Abschnitt werden die Entwicklung sowie Messergebnisse eines Stimmgabel-Rasterkraftmikroskops (AFM) vorgestellt. Dieses ermöglicht die hochau ?ösende topographische Abbildung der Ober?äche mit einer vertikalen Sensitivität im Ångström-Bereich. Das Ziel, mit diesem Gerät KPFM zu betreiben, konnte beim Einsatz an Luft nicht verwirklicht werden.
Subject of this work is the investigation of surface and interface photovoltage (SPV) of thin organic films on metal substrates. Special attention is focused on the system of thin layers of 3,4,9,10-perylenetetracarboxylic-dianhydride (PTCDA) on an Au(110) crystal. For this investigation a novel phase sensitive method was developed based on photoelectron spectroscopy (PES) under additional modulated illumination. It provides the possibility to detect light induced changes in the surface potential with a resolution of about 1mV. This modulated photoelectron spectroscopy is described in detail. Macroscopic Kelvin probe and Kelvin probe force microscopy (KPFM) are presented as further possibilities to measure the surface potential. The photovoltage is investigated by these techniques regarding three parameters: Due to the fact that the barrier at the interface is responsible for the formation of the photovoltage and that the height of this barrier is reduced by the photovoltage, the measurement of the dependence of the SPV on the intensity of the incident light provides information about the energetic structure of the interface. Together with the values of the work function and the ionisation energy of PTCDA, also gained with this methods, a band diagram of the interface can be developed. The wavelength dependent measurements show that excitons can be generated in multiple states. They are excited at different photon energies and have different diffusion lengths. The excitons have to diffuse to the interface to dissociate. Therefore the different excitation states contribute to SPV with different amounts. The investigations upon the generation and decay of the photovoltage shows that the SPV signal appears immediately after switching on the illumination. The decay of the photovoltage after switching off the light is much slower. This implies that the charge carriers are trapped as they remain in the organic film after charge separation at the interface. They have to be thermally activated from this traps. In an extra chapter the development and measurement results of a tuning fork scanning force microscope (AFM) are described. This AFM features high resolution topography images with a vertical sensitivity in the range of single angstroms.

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43

Ferguson, Ryan Sean. "Characterisation of silicon-germanium heterostructures by kelvin force microscopy." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407665.

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44

Zerweck-Trogisch, Ulrich. "Auflösungsvermögen und Genauigkeit der Kelvinsonden-Rasterkraftmikroskopie und deren Anwendung an molekularen Systemen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1196782873906-79057.

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Die Arbeit befasst sich mit der Erforschung und Anwendung der Kelvinsonden-Rasterkraftmikroskopie. Die Technik wird bezüglich der Quantität der gemessenen Werte und der erzielbaren lateralen Auflösung untersucht und auf diverse Probensysteme angewandt. Die so erhaltenen nanoskopischen Werte werden mit markoskopischen Messergebnissen verglichen. Sowohl die elektrostatische Kraft zwischen der Messspitze und der Probenoberfläche als auch deren Gradienten können zur Minimierung der elektrostatischen Wechselwirkung herangezogen werden. Die Detektion des Kraftgradienten zum Aufbau eines Regelkreises erweist sich gegenüber der Kraftdetektion überlegen. Die experimentell ermittelten Befunde werden durch eine Rechnersimulation bestätigt. Diese zeigt die Möglichkeit von quantitativen Ergebnissen für laterale Objektgrößen im Bereich von einigen Nanometern. Im Experiment kann dies gezeigt werden. Es folgt die Anwendung der Kelvinsonden-Rasterkraftmikroskopie: Nanoskopisch ermittelte Werte der Austrittsarbeitsänderung von Metalleinkristall-Oberflächen durch die Adsorption von C_60 entsprechen Literaturwerten, die mit makroskopisch messenden Methoden ermittelt wurden. Sich zeitlich ändernde Oberflächenpotentiale von einer organischen Solarzelle und von lateral unterschiedlich dotiertem Silizium lassen sich quantitativ messen. Der sich bei der Adsorption von Oktadezyl-Phosphonsäure auf Glimmer und Graphit bildende elektrostatische Dipol wird untersucht und abgebildet. Das Wachstumsverhalten und die Austrittsarbeit der organischen Moleküle PTCDA und Alq_3 auf den teilweise mit KBr bedeckten Metallsubstraten Au und Ag wird untersucht. Schlussendlich wird gezeigt, dass mit der Kelvinsonden-Rasterkraftmikroskopie sogar der molekülinterne Dipol der vier Butyl-Gruppen von Tetra-3,5-di-ter-butyl-phenyl-Porphyrinen aufgelöst werden kann.

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45

Bain, Stephen. "Kelvin force microscopy of polymer and small molecule thin-film transistors." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/341044/.

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By their nature, scanning probe microscopy (SPM) measurements are ideally suited to the study of organic thin-film transistors (TFTs). In Chapter 3 surface potential measurements are made on TFTs made from the polymer pBTTT. The modification of the surface morphology by annealing into the liquid crystalline phase is examined and the separation between crystalline layers is found to be in agreement with the literature. Kelvin force gradient microscopy (KFGM) measurements provide a very detailed picture of the local potential within the channel of the TFT, allowing for the separation of the device and �film mobilities in both the linear and saturation regimes. Once the effects of the contacts are removed, the linear mobility is found to be four times higher than the saturation mobility, although the model that best fits the data assumes a constant mobility. Short channel effects are studied in saturation and an upper bound placed on the magnitude of the channel-length modulation. The contacts are also studied in more detail and it is found that a broad region of the pBTTT film near the contacts shows increased resistance, modulated by the gate voltage. In Chapter 4, KFGM is applied to TFTs produces with zone-cast TIPS pentacene as the active material. The seemingly uniform linear crystallites are found to exhibit a wide range of different behaviours, resulting in device characteristics based on statistical averages of many crystallites. The AFM is used to define a single-crystal device and this is found to contain two distinct regions of widely divergent mobility. The highest mobility regions imply that the maximum theoretical mobility is much higher than is achieved with zone-casting. Greater control over the crystallisation of the film could result in significant increases in device performance. Scanned gate microscopy measurements are also performed and susceptibility to local gating is linked to the conductivity of the film.

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46

Hu, Yuanyuan. "Scanning Kelvin probe microscopy studies on device physics of organic field-effect transistors." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709226.

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47

Kerssemakers, Jacob Willem Jozef. "Concepts of interactions in local probe microscopy." [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1997. http://irs.ub.rug.nl/ppn/16440130X.

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Hadizadeh, Rameen. "Novel probe structures for high-speed atomic force microscopy." Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37203.

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Atomic Force Microscopy (AFM) has become an indispensable metrology tool for nanoscale surface characterization. Today, research and industry demand faster and more accurate metrology and these demands must be met expediently. Traditional AFM cantilevers and associated actuators (i.e. piezoelectric) are limited in regards to actuation speed and resonance frequency presenting the user with an undesired trade-off of speed versus resolution. Based on a pre-existing technology known as the FIRAT (Force Sensing Integrated Readout and Active Tip) AFM probe, this work aims to remedy actuation and response issues by implementing a cantilever-on-cantilever probe as well as a novel seesaw probe. Both cases implement electrostatic actuation, eliminating the need for piezoelectrics while demonstrating large - micron scale - actuation and sensitive displacement detection. These new probe designs can potentially demonstrate a wide bandwidth frequency response (e.g. 100 kHz) ideal for high-speed video-rate imaging. Unlike traditional AFM cantilevers, this is realized by mechanically coupling two physically separate structures to provide a soft resonator sensor atop a stiff actuator structure. Common surface-micromachining techniques are utilized to solve the logistical challenge of fabricating these stacked structures. By manipulating the viscous damping and mechanical mode coupling it becomes feasible to attain the aforementioned desired dynamic characteristics.

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Kameni, Boumenou Christian. "Scanning probe force microscopy of III-V semiconductor structures." Thesis, Nelson Mandela University, 2017. http://hdl.handle.net/10948/13992.

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In this dissertation, cross-sectional potential imaging of GaAs-based homoepitaxial, heteroepitaxial and quantum well structures, all grown by atmospheric pressure Metal-organic Vapor Phase Epitaxy (MOVPE) is investigated. Kelvin probe force microscopy (KPFM), using amplitude modulation (AM) and frequency modulation (FM) modes in air and at room temperature, is used for the potential imaging. Studies performed on n-type GaAs homoepitaxial structures have shown two different potential profiles, related to the difference in electron density between the semi-insulating (SI) substrate and the epilayers. It is shown that the contact potential difference (CPD) between the tip and sample is higher on the semi-insulating substrate side than on the n-type epilayer side. This change in CPD across the interface has been explained by means of energy band diagrams indicating the relative Fermi level positions. In addition, it has also been found that the CPD across the interface increases with electron density. This result is in qualitative agreement with theory. In addition, as known from literature, even under ambient conditions FM mode KPFM provides better lateral resolution and more realistic CPD values than AM mode KPFM. Compared to the case of AM mode analysis, where the experimental CPD values were on average of the theoretical values, the CPD values from FM mode analysis are on average of the theoretical ones. Furthermore, by using FM mode, the transition across the interface is sharper and the surface potential flattens/saturates as expected when scanning sufficiently far away from the junction. The non-neutral space charge region of the sample with an electron density of for example, is as measured by FM-KPFM, whereas for AM-KPFM, the width is even more than and the potential profiles do not saturate. For the p-type GaAs homoepitaxial structures, FM mode measurements from a sample with a dopant density of are presented. As in the case of n-type GaAs,a similar potential profile showing two main domains has been obtained. However, unlike the case of type GaAs where the potential measured on the epilayer side is higher than that on the substrate side, the potential on the epilayer side of the junction is lower in this case due to the fact that the Fermi level of p-type GaAs is below that of the substrate.

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Antognozzi, Massimo. "Investigation of the shear force contrast mechanism in transverse dynamic force microscopy." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340356.

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Dissertations / Theses on the topic 'Kelvin force probe microscopy'

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