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1
Gillispie, Meagen Anne. "Metal oxide-based transparent conducting oxides." [Ames, Iowa : Iowa State University], 2006.
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2
Lajn, Alexander. "Transparent rectifying contacts on wide-band gap oxide semiconductors." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-102799.
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Die vorliegenden Arbeit befasst sich mit der Herstellung und Charakterisierung von transparenten Metall-Halbleiter- Feldeffekttransistoren. Dazu werden im ersten Kapitel
transparente gleichrichtende Kontakte, basierend auf dem Konzept von Metalloxidkontakten, hergestellt und im Hinblick auf chemische Zusammensetzung des Kontaktmaterials, Barriereninhomogenität und Kompatibilität mit amorphen Halbleitern untersucht. Außerdem wird die
Anwendbarkeit der Kontakte als UV-Sensor studiert. Im zweiten Kapitel werden transparente leitfähige Oxide vorgestellt und insbesondere deren optische und elektrische Eigenschaften
in Abhängigkeit von den Herstellungsbedingungen studiert. Das dritte Kapitel beinhaltet Untersuchungen zu transparenten Feldeffektransistoren, die auf den im ersten Kapitel untersuchten transparenten gleichrichtenden Kontakten basieren (TMESFETs). Insbesondere die elektrischen Stabilität der Bauelemente hinsichtlich Beleuchtung, erhöhten Temperaturen und Spannungsstress wird untersucht. Auch die Langzeitstabilität, Reproduzierbarkeit und der
Effekt gepulster Spannungen wird betrachtet. Weiterhin wird die Verwendung amorpher Halbleiter im Kanal und damit auch die Herstellung flexibler Transistoren auf Folie demonstriert.
Zuletzt werden die TMESFETs integriert und als Inverterschaltkreise aufgebaut und untersucht. Außerdem wird die Eignung der Transistoren zur Messung von Aktionspotentialen von Nervenzellen studiert.
3
Boltz, Janika [Verfasser]. "Sputtered tin oxide and titanium oxide thin films as alternative transparent conductive oxides / Janika Boltz." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1019850485/34.
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Le, Boulbar Emmanuel. "Croissance par ablation laser pulsé de nouvelles phases d'oxyde de titane pour l'électronique transparente et la conversion de photons." Phd thesis, Université d'Orléans, 2010. http://tel.archives-ouvertes.fr/tel-00667730.
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Le photovoltaïque nécessite de nouveaux matériaux pour diminuer ces coûts et améliorer les rendements. Ces travaux de thèse ont concerné le développement de nouvelles phases d'oxyde de titane pour l'électronique transparente et la conversion de photon appliquée au PV silicium. L'ablation laser pulsé est une méthode de croissance particulièrement adaptée pour la prospection de matériaux aux propriétés innovantes. Le contrôle des phases anatase, rutile et d'une phase de composition TiO1.45 épitaxié en fonction de la pression partielle d'oxygène a permis de réaliser des films aux propriétés électriques, optiques innovantes. Un film biphasé anatase/rutile dopé niobium (TNO1.80) présente ainsi une transition métal-semi-conducteur aux alentours de 68K. Par ailleurs, le film de composition TiO1.45 épitaxié s'est révélé être un oxyde transparent conducteur de type p. La découverte de ce nouveau p-TCOs a été valorisée et validée par l'élaboration d'une homojonction p - n transparente. Les matrices d'oxyde de titane rutile et anatase ont également été utilisées pour accueillir des ions terres rares Ln3+ afin de convertir les photons ultra-violet du spectre solaire incident vers le proche infrarouge (800 > λ > 1100 nm). Le transfert d'énergie des matrices TiO2 vers les dopants Ln3+ a été étudié en fonction de la structure, de la quantité de dopant ainsi que la qualité de la microstructure des films dopés Ln3+ (Ln3+=Pr3+,Tm3+,Eu3+,Yb3+,Nd3+).
5
Isherwood, Patrick J. M. "Development of transparent conducting oxides for photovoltaic applications." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18886.
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Metal oxides are a very important class of materials with a wide range of photovoltaic applications. Transparent conducting oxides (TCOs) are the primary front contact materials used in thin film solar cells. Identification of methods for reducing the resistivity of these materials would have significant benefits. Development of p-type TCOs would provide alternative back contact materials and could enable further development of technologies such as bifacial, window and multijunction cells. A series of studies into these areas is presented in this work. Aluminium doped zinc oxide (AZO) is a well-known n-type TCO consisting entirely of Earth-abundant materials. Targets were manufactured from AZO powder, which was synthesised using a patented emulsion detonation process developed by Innovnano S.A. All films showed good optical transmission. Resistivity was found to decrease with both increasing time and temperature up to 300 degree C. Temperatures above 300 degree C were found to be detrimental to film formation, with increasing amounts of damage to the crystal structure and consequent increases in the resistivity. The effect of alloying molybdenum oxide with molybdenum nitride through reactive sputtering in a mixed oxygen-nitrogen atmosphere was investigated. All alloys were found to show p-type behaviour. Resistivity was found to improve with increased nitrogen content, in contrast to optical transmission, which reduced. A selection of compositions were deposited onto CdTe cells as back contacts. These cells showed an increase in efficiency with increasing nitrogen content. Work function was found to increase with increasing oxygen content, but all work functions were low. Resistivity was shown to correlate strongly with efficiency, caused by a corresponding increase in cell voltage. This implies that to form an ohmic contact on CdTe with p-type materials, work function may be less important than resistivity. The copper oxides are p-type, but uses are limited by the narrow band gaps. Cupric oxide was chosen for investigation and for alloying with other oxides with the aim of increasing the band gap. It was found that temperature and deposition environment have significant impacts on sputtered cupric oxide (CuO) films, with low temperatures and high oxygen environments producing the lowest resistivities. Extrinsic sodium doping was found to reduce the resistivity by up to four orders of magnitude. High oxygen content sodium-doped films were found to have carrier concentrations two orders of magnitude higher than that of indium tin oxide.
6
Liu, Yujing. "Nanostructured transparent conducting oxide electrodes through nanoparticle assembly." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-149076.
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Slocombe, Daniel. "The electrical properties of transparent conducting oxide composites." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/42932/.
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The principal aim of this thesis is the investigation of the electrical properties of conducting pigments provided by Merck KGaA. These pigments are generally micron-sized mica particles coated with a transparent conducting oxide (TCO) and are conventionally dispersed in a polymer matrix at varying volume fractions to form composite structures. To measure the electrical properties of composites and powder materials is not easy since one cannot simply attach terminals as in the measurement of bulk materials. We therefore turn to high frequency techniques, which are capable of measuring composites and powders of conducting particles, but are also capable of measuring non-conducting particles. This thesis therefore has three main themes; 1) the development and use of high frequency measurement techniques for the application to Merck pigments, 2) the investigation of the fundamental electrical properties of TCOs, and 3) the study of the complex electrical behaviour of composites.
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Deyu, Getnet Kacha. "Defect Modulation Doping for Transparent Conducting Oxide Materials." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI071.
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Le dopage des matériaux semi-conducteurs est une partie fondamentale de la technologie moderne. Les oxydes conducteurs transparents (TCO) constituent une famille de semi-conducteurs, qui sont optiquement transparents et électriquement conducteurs. La conductivité électrique élevée est généralement obtenue grâce à un dopage associant des impuretés de substitution hétérovalentes comme dans In2O3 dopé au Sn (ITO), SnO2 dopé au fluor (FTO) et ZnO dopé à l'Al (AZO). Cependant, ces approches classiques ont dans de nombreux cas atteint leurs limites tant en ce qui concerne la densité de porteurs de charge atteignable, que pour la valeur de la mobilité des porteurs de charge. Le dopage par modulation est un mécanisme qui exploite l'alignement de la bande d'énergie à une interface entre deux matériaux pour induire une densité de porteurs de charges libres dans l’un d’entre eux ; un tel mécanisme a permis de montrer dans certains cas que la limitation liée à la mobilité pouvait ainsi était évitée. Cependant, la limite de densité de porteuse ne peut pas être levée par cette approche, du fait de l'alignement des limites de dopage par défauts intrinsèques. Le but de ce travail était de mettre en œuvre cette nouvelle stratégie de dopage pour les TCO. La stratégie repose sur l’utilisation de large bande interdite pour doper la surface des couches de TCO, ce qui résulte à un piégeage du niveau de Fermi pour la phase dopante et à un positionnement du niveau de Fermi en dehors de la limite de dopage dans les TCO. La méthode est testée en utilisant un TCO comme In2O3 non dopé, In2O3 dopé au Sn et SnO2 phase hôte et Al2O3 et SiO2-x en tant que phase de dopant gap à large bandeThe doping of semiconductor materials is a fundamental part of modern technology.Transparent conducting oxides (TCOs) are a group of semiconductors, which holds the features of being transparent and electrically conductive. The high electrical conductivity is usually obtained by typical doping with heterovalent substitutional impurities like in Sn-doped In2O3 (ITO), fluorine-doped SnO2 (FTO) and Al-doped ZnO (AZO). However, these classical approaches have in many cases reached their limits both in regard to achievable charge carrier density, as well as mobility. Modulation doping, a mechanism that exploits the energy band alignment at an interface between two materials to induce free charge carriers in one of them, has been shown to avoid the mobility limitation. However, the carrier density limit cannot be lifted by this approach, as the alignment of doping limits by intrinsic defects. The goal of this work was to implement the novel doping strategy for TCO materials. The strategy relies on using of defective wide band gap materials to dope the surface of the TCO layers, which results Fermi level pinning at the dopant phase and Fermi level positions outside the doping limit in the TCOs. The approach is tested by using undoped In2O3, Sn-doped In2O3 and SnO2 as TCO host phase and Al2O3 and SiO2−x as wide band gap dopant phase
9
Yavas, Hakan. "Development Of Indium Tin Oxide (ito) Nanoparticle Incorporated Transparent Conductive Oxide Thin Films." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614475/index.pdf.
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Indium tin oxide (ITO) thin films have been used as transparent electrodes in many technological applications such as display panels, solar cells, touch screens and electrochromic devices. Commercial grade ITO thin films are usually deposited by sputtering. Solution-based coating methods, such as sol-gel however, can be simple and economic alternative method for obtaining oxide films and also ITO. In this thesis, &ldquoITO sols&rdquo
and &ldquo
ITO nanoparticle-incorporated hybrid ITO coating sols&rdquo
were prepared using indium chloride (InCl3
10
Potter, D. "Zinc-based thin films for transparent conducting oxide applications." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10041886/.
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This thesis describes the synthesis of zinc-based transparent conducting oxide (TCO) thin films, as sustainable alternatives to commercial TCOs. There are two main aims to this work. The first is the discovery of suitable TCO materials, which involves finding the optimum optoelectronic properties for applications in photovoltaic devices. The second aim is investigating the scale up of aerosol assisted chemical vapour deposition (AACVD), which is the technique used to deposit the majority of the films in this work. The films deposited in this work were characterised by X-ray diffraction (XRD) to find the crystal structures, X-ray photoelectron spectroscopy (XPS) to find the elemental compositions, scanning electron microscopy (SEM) to analyse the surface morphologies, UV/vis spectroscopy to find the optical properties, and by Hall effect measurements to find the electrical properties. Aluminium, gallium, indium, silicon, and fluorine have been examined as dopants for ZnO, in various combinations, and at different concentrations. The films were generally found to have high transparency, and electrical properties that approached those of industrial TCO materials. The merits of the films are particularly promising, when considering the relative ease through which the films were synthesised. Additionally, the effect of varying the solvent used to make up the precursor solution is investigated. The deposition of ZnSb2O6 thin films via spin coating is also discussed. This thesis also details an investigation into the scale-up of AACVD. An aerosol transport study was performed, whereby the aerosol was transported prior to deposition. It was found that a considerable amount of aerosol was condensing within the tubing, prior to reaching the reactor. Additionally, increasing the film growth rates was investigated by depositing FTO films using high concentrations in the precursor solution. Growth rates of approximately 2 μm min-1 were achieved, making the use of AACVD for commercial applications significantly more feasible.
11
Shaw, Andrew. "Atomic layer deposition zinc oxide devices for transparent electronics." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3023025/.
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Zinc oxide (ZnO) films deposited using atomic layer deposition (ALD) and plasma enhanced (PE)-ALD for transparent electronics have been explored in this thesis by characterising the films electrically and physically. Thin-film transistors (TFTs) and Schottky diodes have been successfully demonstrated using ALD based thin-films as active layers. The challenge of reducing the intrinsically high conductivity is addressed through two approaches namely the use of substitutional dopants via ALD and tuning of the plasma conditions during PEALD deposition. Initial characterisation established that using Mg as a substitutional alloy, reduced the films conductivity. TFTs were fabricated using lithography, on highly doped Si wafers with thermally grown SiO2 as the gate oxide. The effect of using Mg was to reduce the off-current by a factor of 105. An optimum ratio between the Mg and Zn precursor of 12.5 % was established, defined by a maximum saturation mobility (μsat) of 4 cm2/Vs. In addition, the band gap of the Mg doped ZnO film increased from 3.3 eV to 3.44 eV, through the formation of MgO states within the film. The first instance of Nb doped ZnO for TFTs applications are reported in this thesis. TFTs were fabricated in the same manner as for Mg doped ZnO, however, a capping layer of 5 nm of Al2O3 prior to NbZnO deposition was required to mitigate gate oxide leakage and improve the interface quality. Optimal characteristics were achieved with a lower ratio of 3.8 % between the Nb and Zn precursor. A maximum μsat of 8 cm2/Vs was achieved. The higher mobility and lower precursor percentages for Nb originate from the higher oxidation state of the dopant. A lower sub-threshold swing of 220 mV/dec was achieved for Nb doped films compared to 900 mV/dec for Mg doped films, supporting the advantage of using Nb to control the conductivity of ZnO ALD thin-films for TFT applications. In addition, the sub-band gap states in ZnO film was modelled from current-voltage and capacitance-voltage measurements, where good correlation between both techniques was achieved. Optimisation of PEALD ZnO for Schottky diode applications was established with a deposition temperature of 80 oC and plasma time of 50 s. The use of oxidised metals for the Schottky contact, namely AgxO and Pt¬O¬x was required to obtain good Schottky parameters. These contact metals aim to mitigate the oxygen deficiencies at surface of ZnO. Relatively low ideality factors of < 1.4 are achieved using both Schottky contacts. Thermionic emission was established as the dominant conduction mechanism. The relatively large ideality factors are thought to originate from the polycrystalline nature of the ZnO film.
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Vai, Alex T. "Performance limitations in practical transparent conducting oxide thin films." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:b217b317-5b36-4c9f-b1e5-b21fc65ff07b.
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Zinc oxide (ZnO) has long been advanced as a low cost, earth-abundant transparent conducting oxide (TCO) with potential as a replacement for high-performance, but costly, indium oxide (In2O3) based materials in a wide range of technological applications. However, despite decades of research and development efforts, ZnO-based materials have still failed to displace the incumbents in any large-scale applications. Given the compelling materials cost advantages of ZnO, it is almost certain that its poor adoption is due to deficits in its technical performance. This thesis aims to fulfill the need for systematic, fundamental work to identify and examine the factors that limit TCO performance, and in particular, those that limit ZnO relative to In2O3. Using spray pyrolysis as the primary deposition method, many different series of ZnO and In2O3 films have been prepared and examined using a range of chemical, structural, and optoelectronic characterization techniques. After essential background information on the basic physics and chemistry of TCOs, as well as a detailed discussion of the chosen deposition and characterization methods, three main classes of performance limitations will be covered: 1) those related to the intrinsic properties of electronic transport in crystalline TCO domains, 2) those arising in the course of impurity doping, and 3) those occurring due to grain boundary effects and the polycrystalline nature of thin film TCO samples. Taken together, these results will show that preparing ZnO-based TCOs with performance approaching that of the best In2O3-based materials, while very likely to be technically possible, will almost certainly involve overcoming significant engineering and process development challenges that, importantly, are not required to make high quality In2O3. Ultimately, whether ZnO will ever find significant, real-world use as a TCO will depend on whether the deep differences between ZnO and In2O3 performance limits that will be highlighted and examined in this thesis can be bridged in a practical and cost-effective manner.
13
Dinh, Minh A. "Hydrogen in transition metal doped transparent conductive oxide SnO₂." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127301.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 83-85).
First-principles, thermodynamic, and kinetic Monte Carlo methods are used to study the behavior of hydrogen defects in doped-tin oxides. The calculated results indicate that Mo-, W-, Nb-, F-doped SnO2 are the best doped-tin oxides at reducing hydrogen solubility in their matrices. We expect these oxides also to be the best for removing hydrogen via proton reduction and hydrogen evolution from their surfaces due to the relatively high electron concentration they can have. Especially, W-doped is also found to perform best as a hydrogen blocker at all temperature range due to its ability to block hydrogen diffusion in the form of substitutional defect at low-temperature regime around 600K, and its nature to increase tin cation vacancies blocking hydrogen diffusion at high-temperature regime around 1200K. The computational approach developed here can accelerate the design of insulating materials where hydrogen reactions and proton transport are important.
by Minh Anh Dinh.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering
14
Barquinha, Pedro. "Transparent oxide thin-film transistors: production, characterization and integration." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/5380.
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Song, Dengyuan Centre for Photovoltaic Engineering UNSW. "Zinc oxide TCOs (Transparent Conductive Oxides) and polycrystalline silicon thin-films for photovoltaic applications." Awarded by:University of New South Wales. Centre for Photovoltaic Engineering, 2005. http://handle.unsw.edu.au/1959.4/29371.
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Transparent conductive oxides (TCOs) and polycrystalline silicon (poly-Si) thin-films are very promising for application in photovoltaics. It is extremely challenging to develop cheap TCOs and poly-Si films to make photovoltaic devices. The aim of this thesis is to study sputtered aluminum-doped ZnO TCO and poly-Si films by solid-phase crystallization (SPC) for application in low-cost photovoltaics. The investigated aspects have been (i) to develop and characterize sputtered aluminum-doped ZnO (ZnO:Al) films that can be used as a TCO material on crystalline silicon solar cells, (ii) to explore the potential of the developed ZnO:Al films for application in ZnO:Al/c-Si heterojunction solar cells, (iii) to make and characterize poly-Si thin-films on different kinds of glass substrates by SPC using electron-beam evaporated amorphous silicon (a-Si) [referred to as EVA poly-Si material (SPC of evaporated a-Si)], and (iv) to fabricate EVA poly-Si thin-film solar cells on glass and improve the energy conversion efficiency of these cells by post-crystallization treatments. The ZnO:Al work in this thesis is focused on the correlation between film characteristics and deposition parameters, such as rf sputter power (Prf), working gas pressure (Pw), and substrate temperature (Tsub), to get a clear picture of film properties in the optimized conditions for application in photovoltaic devices. Especially the laterally non-uniform film properties resulting from the laterally inhomogeneous erosion of the target material are investigated in detail. The influence of Prf, Pw and Tsub on the structural, electrical, optical and surface morphology properties of ZnO:Al films is discussed. It is found that the lateral variations of the parameters of ZnO:Al films prepared by rf magnetron sputtering can be reduced to acceptable levels by optimising the deposition parameters. ZnO:Al/c-Si heterojunction solar cells are fabricated and characterized to demonstrate the feasibility of the fabricated ZnO:Al films for application in heterojunction solar cells. In this application, expensive indium-tin oxide (ITO) is usually used. Under the standard AM1.5G spectrum (100 mW/cm2, 25 ??C), the best fabricated cell shows an open-circuit voltage of 411 mV, a short-circuit current density of 30.0 mA/cm2, a fill factor of 66.7 %, and a conversion efficiency of 8.2 %. This is believed to be the highest stable efficiency ever reported for this type of cell. By means of dark forward current density-voltage-temperature (J-V-T) measurements, it is shown that the dominant current transport mechanism in the ZnO:Al/c-Si solar cells, in the intermediate forward bias voltage region, is trap-assisted multistep tunneling. EVA poly-Si thin-films are prepared on four types of glass substrates (planar and textured glass, both either bare or SiN-coated) based on evaporated Si, which is a cheaper Si deposition method than the existing technologies. The textured glass is realized by the UNSW-developed AIT process (AIT = aluminium-induced texture). The investigation is concentrated on finding optimized process parameters and evaluating film crystallization quality. It is found that EVA poly-Si films have a grain size in the range 0.8-1.5 ??m, and a preferential (111) orientation. UV reflectance and Raman spectroscopy measurements reveal a high crystalline material quality, both at the air-side surface and in the bulk. EVA cells are fabricated in both substrate and superstrate configuration. Special attention is paid to improving the Voc of the solar cells. For this purpose, after the SPC process, the samples receive the two post-crystallization treatments: (i) a rapid thermal anneal (RTA), and (ii) a plasma hydrogenation. It is found that two post-crystallization treatments more than double the 1-Sun Voc of the substrate-type cells. It is demonstrated that RTA improves the structural material quality of the cells. Furthermore, a hydrogenation step is shown to significantly improve the electronic material quality of the cells. Based on the RTA???d and hydrogenated EVA poly-Si material, the first mesa-type EVA cells are fabricated in substrate configuration, by using sputtered Al-doped ZnO as the transparent front contact. The investigation is focused on addressing the correlation between the type of the substrate and cell performance. Optical, electrical and photovoltaic properties of the devices are characterized. It is found that the performance of EVA cells depends on the glass substrate topography. For cells on textured glass, the AIT texture is shown to have a beneficial effect on the optical absorption of EVA films. It is demonstrated that a SiN barrier layer on the AIT-textured glass improves significantly both the crystalline quality of the poly-Si films and the energy conversion efficiency of the resulting solar cells. For cells on planar glass, a SiN film between the planar glass and the poly-Si film has no obvious effect on the cell properties. The investigations in this thesis clearly show that EVA poly-Si films are very promising for poly-Si thin-film solar cells on glass.
16
Sechogela, Thulaganyo P. "Vanadium dioxide nanocomposite thin film embedded in zinc oxide matrix as tunable transparent conductive oxide." Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/4529.
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Philosophiae Doctor - PhDThis project is aimed at fabricating a smart material. Zinc oxide and vanadium dioxide have received a great deal of attention in recent years because they are used in various applications. ZnO semiconductor in particular has a potential application in optoelectronic devices such as light emitting diodes (LED), sensors and in photovoltaic cell industry as a transparent electrode. VO2 also has found application in smart windows, solar technology and infrared smart devices. Hence the need to synthesis or fabricate a new smart material using VO2 and an active ZnO based nano-composites family in which ZnO matrix will be hosting thermally active VO2 nano-crystals is the basis of this study. Since VO2 behave as an MIT Mott’s type oxides and exhibits a thermally driven semiconductor-metal phase transition at about 68 oC and as a direct result ZnO:VO2 nano-composites would exhibit a reversible and modulated optical transmission in the infra-red (IR) while maintaining a constant optical transmission in the UV-Vis range. The synthesis is possible by pulsed laser deposition and ion implantation. Synthesis by pulsed laser deposition will involve thin films multilayer fabrication. ZnO buffer layer thin film will be deposited on the glass and ZnO single crystals and subsequent layer of VO2 and ZnO will be deposited on the substrate. X-ray diffraction (XRD) reveals that the series of ZnO thin films deposited by Pulsed Laser Deposition (PLD) on glass substrates has the hexagonal wurtzite structure with a c-axis preferential orientation. In addition the XRD results registered for VO2 samples indicate that all thin films exhibits a monoclinic VO2 (M) phase. UV-Vis NIR measurements of multilayered structures showed the optical tunability at the near-IR region and an enhanced transparency (>30 %) at the visible range.
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Chari, Tarun. "Reduced graphene oxide based transparent electrodes for organic electronic devices." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104534.
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This thesis explores the utility of reduced graphene oxide and hybrid reduced graphene oxide/single walled carbon nanotubes as a transparent electrode. Graphene oxide was fabricated using the modified Hummers method, transferred to arbitrary substrates by a vacuum filtration method, and reduced chemically and thermally thus creating thin, large area reduced graphene oxide films. Films were characterized electrically, optically, spectroscopically, and topographically. Raman and X-ray photoelectron spectroscopy techniques were utilized to ensure successful fabrication of reduced graphene oxide. The reduced graphene oxide electrodes exhibit sheet resistances on the order of 10 – 100 kΩ/sq with transparencies between 60 – 90 %. To ameliorate these electronic properties, single walled nanotubes were introduced during the filtration process to separate the graphene oxide nanoplatelets and prevent structural deformation during reduction. This nanotube doping yielded a two-fold decrease in sheet resistance for low nanotube to graphene oxide ratios, but increased sheet resistance for higher nanotube to graphene oxide ratios. Reduced graphene oxide electrodes and nanotube/reduced graphene oxide hybrid electrodes were used in organic light emitting diode and organic solar cell applications. Organic light emitting diodes exhibited current efficiencies of about 1 cd/A and organic solar cells exhibited power conversion efficiencies less than 1 % for both reduced graphene oxide and hybrid electrodes.Cette thèse examine l'utilité de l'oxyde de graphène réduit et de l'hybride oxyde de graphène réduit et nanotubes carbone en fonction d'une utilisation comme électrode transparente. L'oxyde de graphène a été fabriqué par la méthode de Hummers modifié puis a été transféré sur un substrat arbitraire par la méthode de filtration avec suction à vide, et a été réduit chimiquement et thermiquement pour créer des feuilles d'oxyde de graphène réduit qui sont minces et qui couvrent une grande surface. Les feuilles ont été caractérisées par des mesures électriques, optiques, spectroscopiques, et topographiques. Les spectroscopies Raman et par photoélectron induits par rayons-X ont été utilisées pour s'assurer que la fabrication de l'oxyde de graphène reduit a été obtenue. Les électrodes d'oxyde de graphène reduit montrent des résistances de feuille de 10– 100 kΩ/sq avec des transparences entre 60 – 90 %. Pour améliorer ces propriétés, des nanotube de carbone monoparois ont été introduits pendant le processus de filtration pour séparer les nanoplatelets d'oxyde de graphène et pour éviter la déformation structurelle pendant la processus de réduction. Ce dopage de nanotubes a diminué la résistance de feuille par un facteur deux pour des proportion faibles de nanotubes avec l'oxyde de graphène, mais a augmenté la resistance pour les hautes proportions. Les électrodes d'oxyde de graphène reduit et les électrodes hybrides nanotubes/oxyde de graphène reduit ont été utilisées dans des dispositifs optoélectroniques organiques; spécialement des diodes électroluminescentes et des cellules solaires. Les diodes électroluminescentes organiques ont des rendements de courant inferieurs à 1 cd/A et les cellules solaire ont des rendements de puissance inferieurs à 1 % pour les deux types d'életrodes: oxyde de graphène réduit et hybrides.
18
Mouzon, Johanne. "Synthesis of ytterbium-doped yttrium oxide nanoparticles and transparent ceramics." Doctoral thesis, Luleå : Division of Engineering Materials, Luleå University of Technology, 2006. http://epubl.ltu.se/1402-1544/2006/64/.
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Riedel, Christoph Alexander. "Transparent conductive oxide based hybrid nanostructures for electro-optical modulation." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/420940/.
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In the last decades, plasmonic resonant nanoantennas have created interest in a wide range of research fields that deal with light confinement on the nanoscale. One promising new research branch involves electrically switchable optical properties, which are scaled down to sub-μm size using plasmonic structures. In this thesis, samples with antenna structures whose resonances can be electrically modulated were designed, fabricated and characterised both electrically and optically. A comprehensive analytical study on the interaction of carrier modulation and optical antennas showed that shifts of the resonance wavelength depend on the antenna aspect ratio and material, and are enhanced if the surrounding medium’s permittivity is near zero. The simulation capabilities of the properties of transparent conductive oxides were successfully utilised to design an ultrathin optical solar reflector that selectively radiates visible and nearinfrared light while strongly absorbing mid-infrared light. The measured solar absorptance was 0.12 and the IR emissivity 0.79. Such selective reflectors can replace currently-used metallised quartz tiles to reduce launch costs of spacecraft. Combining electrical and optical simulation models with nanoscale resolution, a novel modulator structure was designed. By directly electrically addressing nanoantennas, a modulator was enabled to perform in transmission additionally to reflection. Reducing the ITO volume to a gap-filling removed negative impacts of the ITO background, so that the resulting modulator could freely shift the resonance of the antenna. The final structure showed a greatly enhanced amplitude modulation of 45% and a resonance shift of 38nm at 1550nm with an applied electric field of 1Vnm−1. Fabricated structures showed that the placing of an ITO gap-loading can be achieved by taking into account height alignment errors of current e-beam systems. Experiments on a planar electrical modulator with a TiN-HfO2-ITO stack showed first electro-optical modulation results, which can benefit from the design developed with the simulation model. The promising results obtained in this thesis open a new pathway for electro-plasmonic modulation in a variety of structures such as tunable reflectors and transmitters in free space or on silicon waveguides.
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Bashar, Shabbir Ahsanul. "Study of transparent indium tin oxide for novel optoelectronic devices." Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/study-of-transparent-indium-tin-oxide-for-novel-optoelectronic-devices(280e6da3-8da2-4680-9059-242b229ae1b7).html.
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Indium Tin Oxide (ITO) films were deposited on a number of semi-conductor materials using reactive r. f sputtering technique to form both rectifying Schottky and ohmic contacts. These contacts were applied in the fabrication of a number of novel optoelectronic devices: Schottky photo-diodes, transparent gate High Electron Mobility Transistors (HEMTs), heterojunction bipolar transistors (HBTs) being used as heterojunction phototransistors (HPTs), light emitting diodes (LEDs) and vertical cavity surface emitting lasers (VCSELs). A number ofthese novel devices were studied in comparatively greater detail; these were the Schottky diode and the HPT. Deposition conditions necessary to produce ITO films with high conductivity and optical transparency over a wide spectral range were studied and optimised. Separate post deposition techniques were developed to produce near ideal rectifying contacts and ohmic contacts with low contact resistance respectively. A thin film of indium (In) was also used to optimise ITO ohmic contacts to n + - GaAs substrates. Near ideal Schottky diodes were realised on n-GaAs substrates using aluminium (AI) and gold (Au) metal contacts. A simulation model was then developed and implemented to study the behaviour of current transport mechanisms over a wide temperature range. Photodiodes with ITO as the Schottky metal contact were fabricated and a study comprising of both their electrical and optical behaviour was undertaken. Relatively large geometry HBTs and HPTs were fabricated using AIGaAs/GaAs, InGaP/GaAs and InPlInGaAs systems respectively; the latter devices were first reported as a result of this study. A comparative study between devices fabricated from these systems were then made. This was followed by an appraisal of the electrical properties of each of their optical counterparts which had ITO emitter contacts. The specific photo responsivity and the spectral responses of these HPTs were analysed. In light of HPTs with transparent ITO emitter ohmic contacts, a brief examination of the merits of vertical versus lateral illumination was also made in this work. Finally a spectral response model was developed to understand and help design optoelectronic detectors comprising of single layer devices (n-GaAs Schottky photo diodes) or multiple semiconductor materials (HPTs using AIGaAs/GaAs or InPlInGaAs systems) to help predict responsivities at a given incident wavelength. As well as material properties of the constituent semiconductors, this model takes into account the specific lateral and vertical geometrical dimensions of the device.
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Rajala, Jonathan Watsell. "ELECTROSPINNING FABRICATION OF CERAMIC FIBERS FOR TRANSPARENT CONDUCTING AND HOLLOW TUBE MEMBRANE APPLICATIONS." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1480909959851349.
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Shih, Grace Hwei-Pyng. "Nanostructure and Optoelectronic Phenomena in Germanium-Transparent Conductive Oxide (Ge:TCO) Composites." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228175.
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Nanostructured composites are attracting intense interest for electronic and optoelectronic device applications, specifically as active elements in thin film photovoltaic (PV) device architectures. These systems implement fundamentally different concepts of enhancing energy conversion efficiencies compared to those seen in current commercial devices. This is possible through considerable flexibility in the manipulation of device-relevant properties through control of the interplay between the nanostructure and the optoelectronic response. In the present work, inorganic nanocomposites of semiconductor Ge embedded in transparent conductive indium tin oxide (ITO) as well as Ge in zinc oxide (ZnO) were produced by a single step RF-magnetron sputter deposition process.It is shown that, by controlling the design of the nanocomposites as well as heat treatment conditions, decreases in the physical dimensions of Ge nanophase size provided an effective tuning of the optical absorption and charge transport properties. This effect of changes in the optical properties of nanophase semiconductors with respect to size is known as the quantum confinement effect. Variation in the embedding matrix material between ITO and ZnO with corresponding characterization of optoelectronic properties exhibit notable differences in the presence and evolution of an interfacial oxide within these composites. Further studies of interfacial structures were performed using depth-profiling XPS and Raman spectroscopy, while study of the corresponding electronic effects were performed using room temperature and temperature-dependent Hall Effect. Optical absorption was noted to shift to higher onset energies upon heat treatment with a decrease in the observed Ge domain size, indicating quantum confinement effects within these systems. This contrasts to previous investigations that have involved the introduction of nanoscale Ge into insulating, amorphous oxides. Comparison of these different matrix chemistries highlights the overarching role of interfacial structures on quantum-size characteristics. The opportunity to tune the spectral response of these PV materials, via control of semiconductor phase assembly in the nanocomposite, directly impacts the potential for the use of these materials as sensitizing elements for enhanced solar cell conversion efficiency.
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Zhao, Xueying. "STRETCHABLE AND TRANSPARENT SILICONE/ZINC OXIDE NANOCOMPOSITE FOR ADVANCED LED PACKAGING." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52120.
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At present, one of the key challenges in the light-emitting diode (LED) packaging technology is light extraction due to the difference in index of refraction between LED chip and air. Silicone nanocomposites have been extensively researched for applications in LED encapsulant to reduce such difference in refractive index. It is well-known that silicone is desirable for LED encapsulant because of its optical transparency and photothermal resistance. However, not much has been accomplished to leverage the elastic properties of silicone for enabling a stretchable LED encapsulant. In this work, I aim to investigate the stretch ability of silicone/zinc oxide (ZnO) nanocomposites for LED packaging. Wurtzite ZnO nanoparticles were prepared in colloids and subjected to silane treatment. Effects of both ex situ and in situ silane treatment on the final mechanical and optical properties of the silicone/ZnO nanocomposites were examined. Silicone/ZnO nanocomposites exhibit significantly more compliant stress-strain behavior than silicone control. In particular, silicone/silane-treated ZnO nanocomposites show more serrated stress-strain curves. They also embrace higher transmittance than silicone/unmodified ZnO nanocomposites, indicating an improvement in the dispersion of the nanoparticles. It was found that the silicone/5% silane-treated ZnO nanocomposite prepared by an in situ method was able to deform over a range of up to 160%. The film made of this unique silicone/ZnO nanocomposite (~40 microns thick) exhibits transmittance >70% throughout the visible range.
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Balestrieri, Matteo. "Transparent conductive oxides with photon converting properties in view of photovoltaic applications : the cases of rare earth-doped zinc oxide and cerium oxide." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE019/document.
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L’objectif de cette thèse était d’étudier les propriétés de conversion de photons des ions terres rares insérées dans des matrices d’oxydes transparents en vue d’application photovoltaïques. En particulier, le but était de fonctionnaliser des couches minces déjà utilisées dans les cellules solaires comme couches antireflet ou oxydes transparents conducteurs. Nous avons donc sélectionné deux matériaux (ZnO et CeO2) compatibles avec les cellules solaires au silicium.Ce travail a montré que les couches minces dopes aux terres rares peuvent être utilisées pour convertir les photons dans des applications photovoltaïques, mais qu’il n’est pas facile d’obtenir des rendements élevés.Cependant, nous avons obtenu des informations très importantes sur l’influence de la matrice sur les propriétés de conversion des terres rares et sur les mécanismes de transfert d’énergie entre la matrice et la terre rareThe objective of this thesis was to investigate the photon converting properties of rare earths (RE) ions embedded in transparent oxide hosts in view of potential application on silicon solar cells. In particular, the goal was to functionalize thin films that are already used in solar cells such as anti-Reflection coatings or transparent conductive oxides.Two host materials (ZnO and CeO2) have been selected, which are compatible with silicon solar cells.This work shows that RE-Doped transparent oxide films are a viable low-Cost solution for obtaining photon-Converting layers that can be applied on solar cells, but that achieving high efficiencies is much more difficult than it might appear in theory. Nevertheless, very valuable information has been obtained on the effect of the host material on the photon management properties and on the energy transfer mechanisms in these systems. In particular, the energy level diagram of some of the rare earth ions in the specific matrices has been reconstructed
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Bergerot, Laurent. "Etude de l'élaboration d'oxyde transparent conducteur de type-p en couches minces pour des applications à l'électronique transparente ou au photovoltaïque." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GRENI003/document.
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L'électronique transparente est actuellement limitée par la difficulté de construire une jonction p-n transparente, en raison du manque d'oxyde transparent conducteur (TCO) de type p réellement performant. L'oxyde cuivreux Cu2O est un TCO de type p prometteur, mais sa bande interdite relativement étroite pour un TCO (2,1 eV), limite sa transmittance dans le domaine visible. Dans le cadre de cette thèse, nous cherchons à augmenter cette valeur. Pour cela, nous explorons la méthode MOCVD comme technique de dépôt pour le dopage au strontium et au calcium de l’oxyde cuivreux. Ce dopage est supposé élargir la bande interdite du Cu2O d'après des calculs ab initio effectués à l'institut Tyndall, à Cork. Dans le chapitre I, nous présentons le contexte de cette thèse. Après avoir expliqué les conditions que doit remplir un matériau pour être un TCO de type p, nous présentons l'état de l'art concernant le Cu2O. Dans le chapitre II, nous présentons l'ensemble des techniques utilisées dans le cadre de cette thèse, de l'élaboration (MOCVD, recuits thermiques) à la caractérisation (MEB, MET, AFM, DRX, spectroscopie FTIR, spectroscopie Raman, XPS, spectroscopie UV-vis-NIR, mesures 4 pointes et mesures d'effet Hall). Au cours du chapitre III, l'influence des paramètres de la MOCVD sur la composition et la morphologie a été analysée pour l’élaboration de couches de Cu2O pures, non dopées en vue d'établir les conditions optimales de dépôt. Nous obtenons des couches continues sur substrat de Si/SiO2, alors qu'elles sont systématiquement hétérogènes avec des zones sans dépôt sur silicium. En outre, nous mettons en évidence le risque d'obtenir la phase cuivre métallique lorsque la concentration de précurseur est élevée, la pression partielle d'oxygène faible et/ou la température élevée. Partant de ces conditions optimales, nous étudions dans le chapitre IV l'influence du dopage au strontium sur les propriétés fonctionnelles des couches (résistivité, largeur de bande interdite et transmittance dans le visible). Une chute de la résistivité a été observée lors du dopage au strontium. Les couches non dopées ont des résistivités de l'ordre de 103 Ω.cm ou plus, contre 10 Ω.cm pour les couches contenant entre 6 et 15% de strontium. La conductivité est bien de type p avec une mobilité de l’ordre de 10 cm2.V-1.s-1 et une densité de porteur de quelques 1016 cm-3. L’écart très grand entre cette densité de porteur et la teneur globale en Sr est lié à la présence d’une contamination des couches par du carbonate et du fluorure de strontium mis en évidence par FTIR et XPS. L’influence réelle de ces impuretés n’a pu être déterminée. Enfin il n'a pas été constaté de variation significative des propriétés optiques, la bande interdite restant large d'environ 2,4 eV et la transmittance moyenne entre 500 et 1000 nm de l'ordre de 55%. Des tendances similaires sont observées dans le chapitre V qui aborde le dopage au calcium, avec comme particularité le fait pour un fort taux de dopage et sous assistance UV, d'aboutir à la présence d'espaces vides localisés à l'interface substrat/Cu2O qui pourrait être lié à la décomposition du carbonate de calcium. Finalement, nous procédons à des recuits thermiques des couches, dopées ou non, dans le chapitre VI. Pour les couches non dopées, cela permet de diminuer la résistivité jusqu’à des valeurs de 10-100 Ω.cm. Pour les couches dopées, cela permet aux couches ayant une résistivité initiale de 10 Ω.cm de descendre jusqu'à 1 Ω.cm. Au cours de cette thèse, nous avons établi les effets du dopage au Sr ou Ca qui conduisent à une forte chute de résistivité sans impact sur les propriétés optiques à la différence des résultats prévus par les calculs ab initio. Nous sommes ainsi parvenus à améliorer les propriétés des couches Cu2O transparentes de type pTransparent electronic is currently limited by the lack of a really performant p-type transparent conducting oxide (TCO), which makes the elaboration of a transparent p-n junction challenging. Cuprous oxide Cu2O is a promising p-type TCO, but its optical transmittance in the visible spectrum is limited by its relatively low band gap (2.1 eV). In this thesis, we aim at increasing this value. To achieve that, we explore MOCVD as the growth method for strontium and calcium doping of cuprous oxide. According to ab-initio calculations performed at Tyndall Institute in Cork, doping with these elements is supposed to increase the band gap of Cu2O. In chapter I, we introduce the context of this thesis. After explaining the required conditions that a material must fulfil to be a p-type TCO, we present the state of the art of Cu2O. In chapter II, we present all the techniques used in this work, from the elaboration (MOCVD, thermal annealing) to characterization (SEM, TEM, AFM, XRD, FTIR, Raman spectroscopy, XPS, UV-vis-NIR spectroscopy, 4 point probe and Hall effect measurement). In chapter III, our objective is to synthesize pure, undoped Cu2O thin films. We explore the influence of the MOCVD parameters on the films composition and morphology. We get homogenous films on Si/SiO2 substrates, while we get heterogeneous films with un-deposited parts on silicon substrate. In addition, we show the risk to get the metallic copper phase when precursor concentration is high, oxygen partial pressure is low, and/or temperature is high. This enables us to determine the optimal deposition conditions. Starting from those optimal conditions, we study the influence of strontium doping on the functional properties of the films (resistivity, band gap and visible light transmittance) in chapter IV. A decrease of resistivity was observed with strontium doping. While undoped films show resistivity values of 103 Ω.cm or more, films doped from 6 to 15% strontium show resistivity values of about 10 Ω.cm. P-type conductivity was confirmed through Hall effect measurements, with a mobility close to 10 cm2.V-1.s-1 and a charge carrier density of about 1016 cm-3. The large difference between this carrier density and the Sr concentration can be linked with the presence of a strontium carbonate and fluoride contamination that was detected by FTIR and XPS. The exact influence of those impurities is not well known. In addition, no significant variation of optical properties was observed, the band gap remained close to 2.4 eV and average transmittance in the 500-1000 nm range was about 55%. Similar tendencies were observed for calcium doping, addressed in chapter V. Calcium doping showed the particularity of leading to the presence of cavities localized at the substrate/Cu2O interface, for a high dopant concentration and under UV assistance. Eventually, we performed thermal annealing on some samples, doped and undoped, in chapter VI. For undoped samples, it allowed to decrease resistivity in the 10-100 Ω.cm range. For doped samples, it allows samples showing initial resistivity of about 10 Ω.cm to decrease it to 1 Ω.cm. No impact of thermal annealing on sample morphology or composition was observed. In this thesis, we successfully established the effects of Sr or Ca doping, which lead to a significant decrease of the resistivity without impact on the optical properties, unlike what was predicted by the ab initio calculations. We were thus able to improve the p-type transparent Cu2O thin films properties
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Müller, Vesna. "Mesoporous transparent conducting films of antimony doped tin oxide as nanostructured electrodes." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-158995.
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Liu, Qiudi. "Optimization and Characterization of Transparent Oxide Layers for CIGS solar cells fabrication." Connect to full text in OhioLINK ETD Center, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1187376131.
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Thesis (M.S.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for the Masters of Science Degree in Physics." "A thesis entitled"--at head of title. Bibliography: leaves 99-102.
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Fleming, Sean Robert. "Charge Transfer Properties of the Substituted Perylene Diimide/Transparent Conducting Oxide Interface." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297563.
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The charge collection efficiency at organic semiconductor/transparent conducting oxide (TCO) interfaces is one of the key parameters controlling the overall efficiency of organic photovoltaics (OPVs). Using Cyclic Voltammetry (CV), the electrochemical surface coverage of an organic semiconductor molecule (a substituted perylene diimide, PDI) was evaluated in order to determine an optimal deposition procedure to obtain a monolayer of PDI on the indium-tin oxide (ITO) surface. The electron transfer rate constant of PDI molecules across the PDI/TTO interface was also evaluated using CV.
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Morselli, Serena. "Thermally reduced Graphene Oxide: a well promising way to transparent flexible electrodes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9324/.
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L'elaborato tratta dell'ottimizzazione del processo di riduzione termica dell'ossido di grafene in termini di conduttività e trasmittanza ottica. Definiti gli standard di deposizione tramite spin-coating e riduzione termica, i film prodotti vengono caratterizzati tramite XPS, AFM, UPS, TGA, ne vengono testate la conducibilità, con e senza effetto di gate, e la trasmittanza ottica, ne si misura l'elasticità tramite spettroscopia di forza, tutto al fine di comprendere l'evoluzione del processo termico di riduzione e di individuare i parametri migliori al fine di progredire verso la produzione di elettrodi flessibili e trasparenti a base di grafen ossido ridotto.
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Lim, Sang-Hyun. "Characterization of p-type wide band gap transparent oxide for heterojunction devices." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/dissertations/AAI3359903/.
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Erslev, Peter Tweedie 1979. "The electronic structure within the mobility gap of transparent amorphous oxide semiconductors." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10566.
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xix, 142 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Transparent amorphous oxide semiconductors are a relatively new class of materials which show significant promise for electronic device applications. The electron mobility in these materials is at least ten times greater than that of the current dominant material for thin-film transistors: amorphous silicon. The density of states within the gap of a semiconductor largely determines the characteristics of a device fabricated from it. Thus, a fundamental understanding of the electronic structure within the mobility gap of amorphous oxides is crucial to fully developing technologies based around them. Amorphous zinc tin oxide (ZTO) and indium gallium zinc oxide (IGZO) were investigated in order to determine this sub-gap structure. Junction-capacitance based methods including admittance spectroscopy and drive level capacitance profiling (DLCP) were used to find the free carrier and deep defect densities. Defects located near insulator-semiconductor interfaces were commonly observed and strongly depended on fabrication conditions. Transient photocapacitance spectroscopy (TPC) indicated broad valence band-tails for both the ZTO and IGZO samples, characterized by Urbach energies of 110±20 meV. These large band-tail widths imply that significant structural disorder exists in the atomic lattice of these materials. While such broad band-tails generally correlate with poor electronic transport properties, the density of states near the conduction band is more important for devices such as transistors. The TPC spectra also revealed an optically active defect located at the insulator-semiconductor junction. Space-charge-limited current (SCLC) measurements were attempted in order to deduce the density of states near the conduction band. While the SCLC results were promising, their interpretation was too ambiguous to obtain a detailed picture of the electronic state distribution. Another technique, modulated photocurrent spectroscopy (MPC), was then employed for this purpose. Using this method narrow conduction band-tails were determined for the ZTO samples with Urbach energies near 10 meV. Thus, by combining the results of the DLCP, TPC and MPC measurements, a quite complete picture of the density of states within the mobility gap of these amorphous oxides has emerged. The relationship of this state distribution to transistor performance is discussed as well as to the future development of device applications of these materials.
Committee in charge: Stephen Kevan, Chairperson, Physics; J David Cohen, Member, Physics; David Strom, Member, Physics; Jens Noeckel, Member, Physics; David Johnson, Outside Member, Chemistry
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"Zinc Oxide Transparent Thin Films For Optoelectronics." Doctoral diss., 2010. http://hdl.handle.net/2286/R.I.8636.
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abstract: The object of this body of work is to study the properties and suitability of zinc oxide thin films with a view to engineering them for optoelectronics applications, making them a cheap and effective alternative to indium tin oxide (ITO), the most used transparent conducting oxides in the industry. Initially, a study was undertaken to examine the behavior of silver contacts to ZnO and ITO during thermal processing, a step frequently used in materials processing in optoelectronics. The second study involved an attempt to improve the conductivity of ZnO films by inserting a thin copper layer between two ZnO layers. The Hall resistivity of the films was as low as 6.9×10-5 -cm with a carrier concentration of 1.2×1022 cm-3 at the optimum copper layer thickness. The physics of conduction in the films has been examined. In order to improve the average visible transmittance, we replaced the copper layer with gold. The films were then found to undergo a seven orders of magnitude drop in effective resistivity from 200 -cm to 5.2×10-5 -cm The films have an average transmittance between 75% and 85% depending upon the gold thickness, and a peak transmittance of up to 93%. The best Haacke figure of merit was 15.1×10-3 . Finally, to test the multilayer transparent electrodes on a device, ZnO/Au/ZnO (ZAZ) electrodes were evaluated as transparent electrodes for organic light-emitting devices (OLEDs). The electrodes exhibited substantially enhanced conductivity (about 8×10-5 -cm) over conventional indium tin oxide (ITO) electrodes (about 3.2×10-5 -cm). OLEDs fabricated with the ZAZ electrodes showed reduced leakage compared to control OLEDs on ITO and reduced ohmic losses at high current densities. At a luminance of 25000 cd/m2, the lum/W efficiency of the ZAZ electrode based device improved by 5% compared to the device on ITO. A normalized intensity graph of the colour output from the green OLEDs shows that ZAZ electrodes allow for a broader spectral output in the green wavelength region of peak photopic sensitivity compared to ITO. The results have implications for electrode choice in display technology.Dissertation/Thesis
Ph.D. Materials Science and Engineering 2010
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Caraveo-Frescas, Jesus Alfonso. "Transparent Oxide Semiconductors for Emerging Electronics." Diss., 2013. http://hdl.handle.net/10754/306065.
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Transparent oxide electronics have emerged as promising materials to shape the future of electronics. While several n-type oxides have been already studied and demonstrated feasibility to be used as active materials in thin film transistors, high performance p-type oxides have remained elusive. This dissertation is devoted to the study of transparent p-type oxide semiconductor tin monoxide and its use in the fabrication of field effect devices.
A complete study on the deposition of tin monoxide thin films by direct current reactive magnetron sputtering is performed. Carrier density, carrier mobility and conductivity are studied over a set of deposition conditions where p-type conduction is observed. Density functional theory simulations are performed in order to elucidate the effect of native defects on carrier mobility.
The findings on the electrical properties of SnO thin films are then translated to the fabrication of thin films transistors. The low processing temperature of tin monoxide thin films below 200 oC is shown advantageous for the fabrication of fully transparent and flexible thin film transistors. After careful device engineering, including post deposition annealing temperature, gate dielectric material, semiconductor thickness and source and drain electrodes material, thin film transistors with record device performance are demonstrated, achieving a field effect mobility >6.7 cm2V-1s-1.
Device performance is further improved to reach a field effect mobility of 10.8 cm2V-1s-1 in SnO nanowire field effect transistors fabricated from the sputtered SnO thin films and patterned by electron beam lithography. Downscaling device dimension to nano scale is shown beneficial for SnO field effect devices not only by achieving a higher hole mobility but enhancing the overall device performance including better threshold voltage, subthreshold swing and lower number of interfacial defects.
Use of p-type semiconductors in nonvolatile memory applications is then demonstrated by the fabrication of hybrid ferroelectric field effect transistors composed of organic ferroelectric layer polyvinylidene fluoride trifluoroethylene and inorganic p-type semiconductor tin monoxide. Both rigid and flexible devices are demonstrated, showing the advantages of low temperature oxides over polymer semiconductors by achieving much better performance, such as order of magnitude higher hole mobility.
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Wang, Zhenwei. "P-type Oxide Semiconductors for Transparent & Energy Efficient Electronics." Diss., 2018. http://hdl.handle.net/10754/627379.
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Emerging transparent semiconducting oxide (TSO) materials have achieved their initial commercial success in the display industry. Due to the advanced electrical performance, TSOs have been adopted either to improve the performance of traditional displays or to demonstrate the novel transparent and flexible displays. However, due to the lack of feasible p-type TSOs, the applications of TSOs is limited to unipolar (n-type TSOs) based devices.
Compared with the prosperous n-type TSOs, the performance of p-type counterparts is lag behind. However, after years of discovery, several p-type TSOs are confirmed with promising performance, for example, tin monoxide (SnO). By using p-type SnO, excellent transistor field-effect mobility of 6.7 cm2 V-1 s-1 has been achieved. Motivated by this encouraging performance, this dissertation is devoted to further evaluate the feasibility of integrating p-type SnO in p-n junctions and complementary metal oxide semiconductor (CMOS) devices.
CMOS inverters are fabricated using p-type SnO and in-situ formed n-type tin dioxide (SnO2). The semiconductors are simultaneously sputtered, which simplifies the process of CMOS inverters. The in-situ formation of SnO2 phase is achieved by selectively sputtering additional capping layer, which serves as oxygen source and helps to balance the process temperature for both types of semiconductors.
Oxides based p-n junctions are demonstrated between p-type SnO and n-type SnO2 by magnetron sputtering method. Diode operating ideality factor of 3.4 and rectification ratio of 103 are achieved. A large temperature induced knee voltage shift of 20 mV oC-1 is observed, and explained by the large band gap and shallow states in SnO, which allows minor adjustment of band structure in response to the temperature change.
Finally, p-type SnO is used to demonstrating the hybrid van der Waals heterojunctions (vdWHs) with two-dimensional molybdenum disulfide (2D MoS2) by mechanical exfoliation. The hybrid vdWHs show excellent rectifying performance. Due to the ultra-thin nature of MoS2, the operation of hybrid vdWHs is gate-tunable, and we further discover such gate-tunability depends on the layer number of MoS2, i.e., the screening effect. The detailed study in such hybrid vdWHs provides valuable information for understanding the switching performance of junctions contain 2D materials.
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Wang, Sung-Li, and 王菘豊. "Fabrication and Analysis of Indium Gallium Oxide Transparent Conductive Oxide." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/57150595771755302479.
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碩士國立臺灣大學
光電工程學研究所
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There are two issues in this thesis. The first issue is the growth of indium gallium oxide thin film. We grow indium gallium oxide thin film successfully in two ways. One way is by photoelectrical chemical method (PEC method). The other way is by thermal evaporation. The second issue is the characteristics study of the indium gallium oxide thin film. After the growth of indium gallium oxide, we take some optical measurements such as transmission, reflection, and photoluminescence .Electrical measurements such as circle transmission line method (CTLM) and Hall measurement. Besides, SEM、EDX、XRD、XPS and surface profiler are also done on the samples in order to study the characteristics and quality of the oxide layer. Finally, we make a discussion on the characteristics and quality issue of indium gallium oxide film. Our indium gallium oxide film has 80% of transparency while photon energy below 3.54 eV. And the lowest resistivity(ρ) is 4x10-3Ω-cm .
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Wang, Kai. "Transparent Oxide Semiconductors: Fabrication, Properties, and Applications." Thesis, 2008. http://hdl.handle.net/10012/3676.
Full textAbstract:
Transparent oxide semiconductors (TOSs) are materials that exhibit electrical conduction and optical transparency. The traditional applications of these materials are transparent conducting oxides in flat-panel displays, light-emitting diodes, solar cells, and imaging sensors. Recently, significant research has been driven to extend state-of-the-art applications such as thin-film transistors (TFTs). A new and rapidly developing field is emerging, called transparent electronics. This thesis advances transparent electronics through developing a new technique to fabricate TOSs and demonstrating their applications to active semiconductor devices such as diodes and TFTs.
Ion beam assisted evaporation (IBAE) is used to deposit two common TOSs: zinc oxide (ZnO) and indium oxide (In2O3). The detailed material study is carried out through various characterization of their electrical properties, chemical composition, optical properties, crystal structure, intrinsic stress, topology, and morphology, as well as an investigation of thin-film property as a function of the deposition parameters: ion flux and energy, and deposition rate. The study proves that IBAE technique provides the capability for fabricating TOSs with controllable properties.
By utilizing the newly developed semiconducting ZnO, p-NiO/i-ZnO/n-ITO and n-ITO/i-ZnO/p-NiO heterostructure photodiodes with a low leakage are proposed and assessed. Analysis of their current-voltage characteristics and current transient behaviour reveals that the dominant source of leakage current stems from the deep defect states in the intrinsic zinc oxide layer, where its dynamic response at low signal levels is limited by the charge trapping. The exploration of the photoconduction mechanism and spectral response confirms that such photodiodes are potentially applicable for ultraviolet (UV) sensors. The comparative study of both device structures provides further insights into the leakage current mechanisms, p-i interface properties, and quantum efficiency.
Secondly, with the novel semiconducting In2O3, TFTs are fabricated and evaluated. The device performance is optimized by addressing the source/drain contact issue, lowering the intrinsic channel resistance, and improving the dielectric/channel interface. The best n-channel TFT has a high field-effect mobility of ~30 cm^2/Vs, a high current ON/OFF ratio of ~10^8, and a sub-threshold slope of 2.0 V/decade. More important, high-performance indium oxide TFTs here are integrated with the silicon dioxide and silicon nitride gate dielectrics by conventional plasma-enhanced chemical vapour deposition, which makes indium oxide TFT a competitive alternative for next generation TFTs to meet the technical requirements for flat-panel displays, large area imager arrays, and radio frequency identification tags. The stability study shows that indium oxide TFTs are highly stable with a very small threshold voltage shift under both a long-term constant voltage and long-term current stress. The dynamic behaviour indicates factors that affect the operation speed of such TFTs. A descriptive model is proposed to link the material properties and the processing issues with the device performance to facilitate further research and development of TOS TFTs.
The research described in this thesis is one of the first investigations of the fabrication of TOSs by the IBAE and their applications to a variety of thin-film devices, particularly UV sensors and TFTs.
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Lin, Yin-Chih, and 林盈志. "Preparation and Characterization of Transparent Conducting Oxide." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/24784789539743148298.
Full textAbstract:
碩士國立清華大學
物理學系
95
Transparent Conducting thin film is a remarkable thin film, it has application of solar cell and TFT-LCD. Indium Tin oxide is a important material of TCO. In the experiment,We choose new coating method-Pulse Arc deposition (PAD). It generates ultrahigh current desity to improve the quality of thin film at room temperature. Beside, We find the best coating condition by different bias and different target component. And use Four Point Probe,Hall measurement,AFM,SEM,XRD and spectrometer to measure it . We try to account of optical and electric properties , and drew conclustion from experimental data.
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蔡裕榮. "Sol-Gel-Derived Transparent Conducting Oxide Films." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/07423248085661961901.
Full textAbstract:
碩士國立中正大學
化學研究所
90
Abstract Antimony tin oxide films (ATO) and indium tin oxide films (ITO) have high electrical conductivity and high optical transparency. By sol-gel process, a metal oxide network of ATO or ITO can be obtained via hydrolysis and polycondensation of the precursor (metal alkoxide or metal salt). Such reactions are characterized as nucleophilic substitutions and can be modified by the choice of the precursor, solvent and additives; they can also be explained by the partial charge model based on balance of electronegativity. Partial charge model not only can illustrate how charges distribute in a molecule but can also predict if a reaction will occur. Metal alkoxides have high reactivity and are easily hydrolysed. The nature of the alkoxyl group influences not only the hydrolysis and polycondensation reactions but also the property of the film. Using metal alkoxide〔M(OR)n〕 as the precursor, the hydrolysis ratio h (H2O/M) must go between 1 and n (1＜h＜n) to produce fine gels. Metal salts can also undergo hydrolysis and polycondensation reactions that are strongly dependent on pH. The higher the pH the larger will be the hydrolysis ratio. If highly polycondensed products are desired, the reactions should be carried out at a pH close to the zero charge point of the metal oxide. In order to control and improve the sol-gel process, additives are used to obtain films of higher qualities. Adding PVA (poly-vinyl alcohol) into the sol can efficiently prevent the gel from cracking. Also, additives such as AcOH (acetic acid), acaH (acetyl acetone), can be used to form stable compounds and lower the function of the precursor to facilitate the formation of gel as well as monodispersed particles. The electrical conductivity of these films arises from the high concentration of carriers and oxygen deficiency. As such, moderate doping can efficiently increase the concentration of carriers, and the best proportion of Sb in ATO would be 6at% ~ 10at%, while that of Sn in ITO would be 4at% ~ 8at% or 8wt% ~ 15wt%. Controlling the atmosphere (vacuum, argon, nitrogen, nitrogen/hydrogen) during the process of heat-treatment increases oxygen deficiency. Meanwhile, higher oxygen deficiency also exists near surface of the films. Coating method can also influence the property of the film. Films produced by spin coating not only has smaller electrical resistivity, but also a smooth face as well as fine optical quality. Coated films that go through proper drying and then undergo heat-treatment have a lower possibility of cracking than those that undergo heat-treatment directly without drying first. Furthermore, it is better to dry for 30 minutes at a temperature of 150℃. However, cracks are produced easily if the calefaction speed is too fast. Therefore, it is better to maintain the calefaction speed between 20℃/min and 2.5℃/min, with the temperature between 500℃ and 600℃, and with the calefaction time between 30 and 60 minutes. If laser or infrared ray is used to accelerate heat-treatment, the electrical resistivity of the films is lowered by 2 to 5 times than that by heat-treatment with electric stove. The electrical resistivity of ATO produced by the sol-gel process is still a little high, but the electrical resistivity of ITO produced by the sol-gel process is comparable with other methods. Furthermore, ITO films prepared by the sol-gel-derived target has a film resistivity one third lower than that by the normal target.
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Chou, Yi-Teh, and 鄒一德. "Transparent Amorphous Oxide Semiconductor Thin Film Transistors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/90297740029086982581.
Full textAbstract:
博士國立交通大學
光電工程學系
99
With the coming of digital generation, flat panel display market grows vigorously and promotes quick development of active matrix liquid crystal display (AMLCD), like home television, portable personal digital assistant (PDA), notebook (NB), digital camera, etc. Such development of the electrical consuming products mushrooms like bamboo shoots after a spring rain and makes people live a more convenient life. So far the main addressing component in the pixel is the thin film transistors (TFTs), therefore technologies and fabrication techniques on novel display and TFT become so popular in recent years. However as AMLCD manufactured with conventional amorphous silicon (a-Si:H) for the semiconductor layer, the low mobility property of a-Si:H causes the need of large width over length ratio (W/L) to compensate the lack of driving current. This also decreases the aperture ratio of the pixel and increases backlight intensity, resulting in too much power consumption. For this reason, searching for high performance semiconductor material becomes a critical issue for TFT. In recent year, among several novel candidates for the semiconductor film, transparent amorphous oxide semiconductor (TAOS) attracts lots of attention because of its high mobility, high transparency, and easy process control issue. More and more international research groups including our teams make a lot of effort on this topic. As for applying TAOS film into AMLCD, not only resolution and aperture ratio can be increased, but power consumption can be saved effectively. Besides, for the high conducing current characteristics of a-TCO TFT, it can also be extended to active matrix organic light emission diode (AMOLED) as the pixel switches and peripheral system integration on glass substrate (SOG). In addition, it can also be applied to form several circuits for value-added functions. However the sensitivity of TAOS to ambient air cause a deadly barrier for the actual application in industry. And the exact reason and mechanism for these influence factors are not clear till today. In this study, we tried to clarify the influence factors and related mechanism. Then we applied three solutions to reduce the influence of ambient air. For the first part we used thermal annealing methods to decrease the sensitivity of TAOS film. The improvement of amorphous InGaZnO TFT with environmental influence by annealing methods has been studied in this work. Samples with 250oC annealing had large threshold voltage shifts in ambient atmosphere with time going by. As annealing temperature raises, both the uniformity and device stability improved obviously. By using the XPS analysis, the better oxygen bonding has been observed for samples with higher annealing temperature. Stronger oxygen bond can effectively lead to less inactive oxygen in a-IGZO film and desorption reaction with ambient air in back channel region. The electrical reliability and illumination measurement has been implemented for the certification of mechanism. For the second part, we tried to improve the TAOS film quality by using doping methods. This work presents electrical characteristics of the nitrogenated amorphous InGaZnO thin film transistor (a-IGZO:N TFT). The a-IGZO:N film acting as a channel layer of TFT device was prepared by DC reactive sputter with nitrogen and argon gas mixture at room temperature. Experimental results show the in-situ nitrogen incorporation to IGZO film can properly adjust the threshold voltage and enhance the ambient stability of TFT device. Furthermore, the a-IGZO:N TFT has 44% of increase in the carrier mobility, and the electrical reliability and uniformity also progress obviously, while comparing with those without implementing nitrogen doping process. In the final part, we applied a new structure to protect the TAOS-based TFT from the interference of ambient air. The performance of a-IGZO TFT with an in-situ deposition of IGZON film as the backchannel passivation was demonstrated in this work. Compared to the passivation-free counterpart, a 50% increase in mobility and an obvious decline in Vth and S.S. were observed. Besides, the electrical uniformity and stability were improved significantly. Furthermore, the achievement above can be used for a high-voltage-gain complementary metal oxide semiconductor (CMOS) inverter with an InGaZnO/pentacene heterostructure channels ambipolar thin film transistors (TFTs). The ambipolar TFT exhibits a electron mobility of 23.8 cm2/V.s and hole mobility of 0.15 cm2/V.s for the InGaZnO and pentacene, respectively. The thermal annealing process was also studied to adjust electron concentration reducing operating voltage of the CMOS inverter. The voltage gain achieves as high as 60 obtained in the first and third quadrants of the voltage transfer characteristic. The high performance and simple manufacture of the heterostructure CMOS inverter show promise as critical components in various electrical applications.
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Chu, Ting-Fu, and 朱庭甫. "Copper doped p-type nickel oxide transparent conducting oxide thin films." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/44025406112552036289.
Full textAbstract:
碩士國立臺灣科技大學
光電工程研究所
103
Nickel oxide with/without doping of Cu has been deposited by reactive ion beam sputter deposition. Effects of oxygen partial flow rates, deposition temperatures, and Cu concentrations on the electrical and optical properties of nickel oxide have been characterized. The resistivity of nickel oxide deposited at room temperature was found to decrease as oxygen partial flow rate increases, which is attributed to the increased concentration of nickel vacancies. Cu doped nickel oxide deposited at 150 and 300C by 100% oxygen ion beam results in the formation of single phase crystalline Ni1-xCuxO with x up to 0.5. The resistivity of Ni1-xCuxO was found to decrease as x increases, which is also due to increased metal vacancy defects. The transparency of Ni1-xCuxO was found to increase as deposition temperature increases, while doping of Cu results in decrease of band gap. UPS analysis indicates that high concentration of Cu (x = 0.5) results in the reduction of work function of Ni1-xCuxO from 5.2 to 4.2 eV.
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Lajn, Alexander. "Transparent rectifying contacts on wide-band gap oxide semiconductors." Doctoral thesis, 2012. https://ul.qucosa.de/id/qucosa%3A11820.
Full textAbstract:
Die vorliegenden Arbeit befasst sich mit der Herstellung und Charakterisierung von transparenten Metall-Halbleiter- Feldeffekttransistoren. Dazu werden im ersten Kapitel
transparente gleichrichtende Kontakte, basierend auf dem Konzept von Metalloxidkontakten, hergestellt und im Hinblick auf chemische Zusammensetzung des Kontaktmaterials, Barriereninhomogenität und Kompatibilität mit amorphen Halbleitern untersucht. Außerdem wird die
Anwendbarkeit der Kontakte als UV-Sensor studiert. Im zweiten Kapitel werden transparente leitfähige Oxide vorgestellt und insbesondere deren optische und elektrische Eigenschaften
in Abhängigkeit von den Herstellungsbedingungen studiert. Das dritte Kapitel beinhaltet Untersuchungen zu transparenten Feldeffektransistoren, die auf den im ersten Kapitel untersuchten transparenten gleichrichtenden Kontakten basieren (TMESFETs). Insbesondere die elektrischen Stabilität der Bauelemente hinsichtlich Beleuchtung, erhöhten Temperaturen und Spannungsstress wird untersucht. Auch die Langzeitstabilität, Reproduzierbarkeit und der
Effekt gepulster Spannungen wird betrachtet. Weiterhin wird die Verwendung amorpher Halbleiter im Kanal und damit auch die Herstellung flexibler Transistoren auf Folie demonstriert.
Zuletzt werden die TMESFETs integriert und als Inverterschaltkreise aufgebaut und untersucht. Außerdem wird die Eignung der Transistoren zur Messung von Aktionspotentialen von Nervenzellen studiert.
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Lin, I.-Kuang, and 林玴光. "ITO Transparent Conducting Oxide For Touch Panel Application." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/36546525959596714099.
Full textAbstract:
碩士明新科技大學
電機工程研究所碩士在職專班
101
Transparent conducting indium tin oxide (ITO) thin film were deposited onto blank galss by DC magnetron sputtering for touch panel products. Via the change of the process parameter for example：substrate temperature,oxygen pressure,working pressure......to study resistiveity、transmittance and thickness of thin-film properties. Transparent conducting thin film is semiconductor on electrical properties,it is also easy to show the wards and photo, usually apply to touch panel need highly visible transmission, so the film thickness needs to be very thin, however this has many disadvantages, including unstable electrical properties, non-uniform sheet resistance. Except improve ITO thin-film properties,we also try to find the optimal process parameter for a factory.
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Chien, Huang-pin, and 錢皇賓. "Wet Coating of Transparent Conductive Oxide (AZO) Film." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/41304913102342763093.
Full textAbstract:
碩士國立中央大學
化學工程與材料工程研究所
96
Significant progress has been made in transparent conductive oxide (TCO) films, largely motivated by the emergence of LCD and solar cell industries. In the search for a cheaper and indium-free materials to replace the traditional ITO, aluminum-doped zinc oxide (AZO) has been the leading candidate. Therefore, the objective of this research is to identify experimentally the controlling factors that ultimately govern the transparency and electrical conductivity of AZO film. ZnO nanoparticles of size 5~6 nm have been successfully synthesized previously in our Lab by titrating zinc chloride with sodium hydroxide in ethylene glycol solution, followed by low temperature aging. However, such method has two serious drawbacks – the production of unwanted sodium chloride byproduct, and a low concentration (4 wt%). This would require multiple coatings and sintering needed to achieve the desired thickness. To achieve the desired AZO film thickness with a single coating, the concentration of ZnO solution must be about 50 wt%. At the same time the NaCl byproduct must be remove. Using PGME as a co-solvent to dissolve hexane in EG, ZnO nanoparticles were precipitaled while redisperse after evaporation of hexane. TGA analysis showed an increased in weight percent (64 wt%). After dilution with methanol to 30 wt%, the as-prepared film with one dip-coating cycle was sintered in air at 400oC. The resulting film showed a transparency of higher than 90% and a thickness of 300 nm as measured by SEM. Subsequent study involved the dopping of aluminum and sintering conditions on the electrical conductivity and transparency of AZO films. Variables sadas sintering atomsphere and temperature were also tested to study their respective impacts.
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Deyu, Getnet Kacha. "Defect Modulation Doping for Transparent Conducting Oxide Materials." Phd thesis, 2020. https://tuprints.ulb.tu-darmstadt.de/9700/1/Getnet%20Kacha%20Deyu-Ph.D.%20Thesis.pdf.
Full textAbstract:
The doping of semiconductor materials is a fundamental part of modern technology.
Transparent conducting oxides (TCOs) are a group of semiconductors, which holds the
features of being transparent and electrically conductive. The high electrical conductivity
is usually obtained by typical doping with heterovalent substitutional impurities like in
Sn-doped In2O3 (ITO), fluorine-doped SnO2 (FTO) and Al-doped ZnO (AZO). However,
these classical approaches have in many cases reached their limits both in regard to
achievable charge carrier density, as well as mobility. Modulation doping, a mechanism
that exploits the energy band alignment at an interface between two materials to induce
free charge carriers in one of them, has been shown to avoid the mobility limitation.
However, the carrier density limit cannot be lifted by this approach, as the alignment of
doping limits by intrinsic defects. The goal of this work was to implement the novel
doping strategy for TCO materials. The strategy relies on using of defective wide band
gap materials to dope the surface of the TCO layers, which results Fermi level pinning
at the dopant phase and Fermi level positions outside the doping limit in the TCOs.
The approach is tested by using undoped In2O3, Sn-doped In2O3 and SnO2 as TCO
host phase and Al2O3 and SiO2−x as wide band gap dopant phase.
The study was divided into two parts by the approaches followed experimentally. The
first part deals with a physical approach, in which sputtered TCOs are used as a host
materials and covered with dopant layers. To test the versatility of the approach the
second part deals with a chemical approach, in which SnO2 based nanocomposite films
produced in spray pyrolysis deposition.
In the physical approach, ITO/ALD-Al2O3, In2O3/ALD-Al2O3, and In2O3/sputtered
SiO2−x thin film systems were exploited. The study was conducted mostly by photoelectron
spectroscopy and Hall effect measurements. ITO films prepared in different
conditions showed an increase of conductivity after ALD-Al2O3 deposition at 200 °C.
This was mostly due to an increase in carrier concentrations. However, Al2O3 deposition
also resulted in a chemical reduction of ITO. The diffusivity of compensating oxygen interstitial (Oi) defects at 200 °C is sufficiently screen the high Fermi level induced by Al2O3, which disable the use of defect modulation doping at this temperature. The
results indicate that achieving higher carrier concentration in ITO thin films requires
a control of the oxygen pressure in combination with low-temperature ALD process.
Undoped In2O3 films also showed an increase of conductivity upon deposition of upto
10-cycles of ALD-Al2O3. These increases indicate the occurrence of defect modulation
doping. However, in order to improve the interface properties and firmly prove the
modulation doping effect, more detailed studies required on the doped interfaces. The
approach was further examined by depositing reactively sputtered SiO2−x dopant phase
from Si target on the top of In2O3 films. The resulting conductivity of In2O3/sputtered
SiO2−x do not show enhancement of electrical properties. This is due to the implantation
of oxygen species during SiO2 deposition on the surface of In2O3, which counteract the
defect modulation doping by reducing concentration of oxygen vacancies (VO) in In2O3.
Therefore, further studies on the deposition conditions of the dopant phase is still vital
to see enhanced electrical properties.
In the chemical approach two different routes were followed: embedding nanoparticles
in TCO host matrix and formation of demixed composite films. In the first route,
Al2O3 and TiO2 nanoparticles (NPs) were chosen as dopant phases and were deposited
together with SnO2 TCO precursors. Different characterization of the produced films
do not confirm the presence nanoparticles into tin oxide films. Therefore to realise
modulation effect further optimization deposition conditions and sample preparation
techniques are needed. For the second route, mixture of SnCl4 ·5(H2O) and Al(acac)3
precursor solutions in different composition are used to produce SnO2/Al2O3 demixed
composite films. Different physicochemical studies shows that under the deposition
conditions followed during this study Al3+ preferably substitute Sn4+ than forming
another Al2O3 separated phase. Al was acting as an acceptor doping on SnO2 films.
Therefore, enhanced conductivity was not observed on the probed samples. For this
route further optimization of deposition condition is clearly required.
The results of this dissertation are relevant for the usage of TCOs in the emerging field
of oxide thin film electronics in particular in field where the surface to bulk ratio is much
higher than in conventional films, as the approach is near surface phenomena. However,
further utilization of both the processing conditions and material selection are vital.
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Chen, Bo-Chao, and 陳柏超. "Oxide-reduction Produced the Transparent Conductive Graphene Film." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/58769854968320690907.
Full textAbstract:
碩士崑山科技大學
電子工程研究所
101
This study oxide-reduction produced the transparent conductive graphene film, a oxide-reduction method has the advantages of lower cost and technology,first graphite subjexcted tooxidation treatment,then produced graphene oxide with DI water were mixed, graphene oxide aqueous solution,the graphene oxide aqueous solution of aspin coating on a glass substrate,and in the environment of argon/hydrogen mixed gas reduction by heating to produce the transparent conductive graphene film. First, the X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy analysis of the morphology of the film, the lattice structure and its constituent content by XRD analysis that at 10. Places a strong peak produced can be proved that the graphene oxide, observed by SEM at a concentration of 1 mg / ml are found in significant film channel, and in the lower 0.1,0.5 mg / ml two group of the surface with a uniform particle size, particle composition by EDS analyzes are recognized as carbon, Raman analysis of ID / IG> 1, I2D/IG <1.3, the more defects of the multi-graphene structure, then the UV-VIS spectrometer after that, as the concentration increases, the transmittance decreases, while that by the four-point probe sheet resistance, as the concentration increases, the sheet resistance decreases, the best argument for the reduction temperature 300 ℃ concentration 0.1 mg / ml ( 3 layer )
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"Metal-Oxide Based Transparent Conductive Oxides and Thin Film Transistors for Flexible Electronics." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.8850.
Full textAbstract:
abstract: The object of this study is to investigate and improve the performance/stability of the flexible thin film transistors (TFTs) and to study the properties of metal oxide transparent conductive oxides for wide range of flexible electronic applications. Initially, a study has been done to improve the conductivity of ITO (indium tin oxide) films on PEN (polyethylene naphthalate) by inserting a thin layer of silver layer between two ITO layers. The multilayer with an optimum Ag mid-layer thickness, of 8 nm, exhibited excellent photopic average transmittance (~ 88 %), resistivity (~ 2.7 × 10-5 µ-cm.) and has the best Hackee figure of merit (41.0 × 10-3 Ω-1). The electrical conduction is dominated by two different scattering mechanisms depending on the thickness of the Ag mid-layer. Optical transmission is explained by scattering losses and absorption of light due to inter-band electronic transitions. A systematic study was carried out to improve the performance/stability of the TFTs on PEN. The performance and stability of a-Si:H and a-IZO (amorphous indium zinc oxide) TFTs were improved by performing a systematic low temperature (150 °C) anneals for extended times. For 96 hours annealed a-Si:H TFTs, the sub-threshold slope and off-current were reduced by a factor ~ 3 and by 2 orders of magnitude, respectively when compared to unannealed a-Si:H TFTs. For a-IZO TFTs, 48 hours of annealing is found to be the optimum time for the best performance and elevated temperature stability. These devices exhibit saturation mobility varying between 4.5-5.5 cm2/V-s, ION/IOFF ratio was 106 and a sub-threshold swing variation of 1-1.25 V/decade. An in-depth study on the mechanical and electromechanical stress response on the electrical properties of the a-IZO TFTs has also been investigated. Finally, the a-Si:H TFTs were exposed to gamma radiation to examine their radiation resistance. The interface trap density (Nit) values range from 5 to 6 × 1011 cm-2 for only electrical stress bias case. For "irradiation only" case, the Nit value increases from 5×1011 cm-2 to 2×1012 cm-2 after 3 hours of gamma radiation exposure, whereas it increases from 5×1011 cm-2 to 4×1012 cm-2 for "combined gamma and electrical stress".Dissertation/Thesis
Ph.D. Materials Science and Engineering 2011
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Lin, Mu-Chieh, and 林牧杰. "Growth and Characterization of p-type nickel oxide transparent conducting oxide thin films." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/37040615329300688990.
Full textAbstract:
碩士國立臺灣科技大學
光電工程研究所
104
Nickel oxide has been deposited by reactive ion beam sputter deposition. Effects of oxygen partial flow rates and deposition temperatures on the electrical and optical properties of nickel oxide are characterized. Samples deposited at both 150 and 300C are polycrystalline NiO, while the FWHM of NiO(200) decreases as deposition temperature increases. As oxygen partial pressure increases, the diffraction peak position of NiO(200) shifts to the smaller angle, indicating increased lattice constant, which may due to the presence of oxygen interstitial defects. As oxygen partial pressure increases, local vibration mode at 545 cm-1 shifts to lower energy and its FWHM increases, indicating deteriorated crystalline quality. Oxygen atomic percentage increases as oxygen partial pressure increases, while oxygen atomic percentage drops as deposition temperature increases. The bandgap of NiO deposited at 150 and 300C both increases from 3.6 eV to 4.1 eV as oxygen partial pressure increases. NiO deposited at 150C with 100% oxygen partial pressure exhibits the lowest resistivity of 3.3 Ω∙cm
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Ao, Yi-Chieh, and 敖以杰. "Studied on Characterization of Flexible Transparent Conducting Oxide Film." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/52995587187548771908.
Full textAbstract:
碩士國立高雄應用科技大學
化學工程系碩士班
95
At present, TCO material is often applied in the manufacturing of LCD, plasma screens, and in flat-panel displays as panel electrode film material. However, the main application is using the physical vapor deposition (PVD) based vacuum evaporation method or magnetic enhanced sputtering to deposit thin film metal TCO, such as indium tin oxide (ITO). This glass material substrate has such disadvantages as fragility, heaviness, and the failure to fit in the continuous rolling manufacturing procedure. Along with the introduction of the roll to roll production model into flexible manufacturing procedures of panels, some transparent conducting films using polymer flexible material as the substrate to form flexible transparent conducting film, have the potential to be future electrode materials of flexible displays. Few studies on the physical properties of flexible transparent conducting film have been conducted; therefore, a series of physical properties of flexible transparent conducting film were in this study researched to provide reference for manufacturers to further develop flexible displays. This study makes use of the low resistance range in order to measure the chip resistor of flexible transparent conducting film, for addressing the influence of annealing temperature on resistor. Through the measurement of two-dimension apparatus, we are able to acquire the dimension changes of flexible transparent conducting film before and after annealing, to observe the influence of annealing temperature on the dimension stability of material, to examine whether annealing temperature will change the surface structure, element composition and content, or if it will lead to major defects via SEM and EDS. In addition, aqueous solution containing 5% acetic acid is used for etching conducting film to examine the influence of temperature on the etching speed on conducting film. In the end, Osuka optical inspection equipment and a haze meter are used to the measure the influence of light transmission and haze after substrate is applied on the conducting film.
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Wang, Chin-wen, and 王志文. "Deposition of transparent conductive oxide films by spray pyrolysis." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/57647545803062306579.
Full textAbstract:
碩士國立臺南大學
材料科學系碩士班
100
Transparent conductive films have been widely used in various optoelectronic devices, wherein the fluorine-doped tin oxide (FTO) films are suitable for the solar cells application because of good thermal stability and higher acid resistance. In recent years, some researchers have tried to change the FTO surface texture to improve the performance of solar cells. As for dye-sensitized solar cells, the structure of photoanode is an important parameter for enhancing their performance. In this research, the spray pyrolysis method will be used to prepare the conductive FTO film and the porous layer of aluminum-doped zinc oxide (AZO). For the FTO film, we could enhance its haze by changing the spray parameters. By changing the spray time, the FTO surface would produce some spherical particles which contribute to increasing the haze of FTO films. In infrared region the haze was improved by 7 % and a 12 % improvement was obtained in the visible region. In the spray deposition of AZO coatings, we could get porous layer by adding PVB to zinc salt solution. In addition, we could also take advantage of the rapid deposition of the spray pyrolysis with the sol-gel solution to achieve porous layers.
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Zheng, Jun-Jie, and 鄭俊傑. "Transparent Conductive Oxide Thin Films for Solar Cell Application." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/59161629052745668661.
Full textAbstract:
碩士國立高雄海洋科技大學
微電子工程研究所
99
Zinc oxide is a wide and direct band gap of semiconductor. The excitation wavelength of light is short wavelength, so it is widely used in optical materials. Therefore, this thesis focuses on transparent conductive oxide - zinc oxide(ZnO). This thesis will try doped aluminum, nitrogen atoms in the ZnO film for analysis of materials and research the practical application. This thesis will use Sol-gel method to derive aluminum doped ZnO (AZO, ZnO: Al) and p-type aluminum co-doped ZnO (NZO, ZnO: Al: N) film. For different preparation conditions and heat treatment conditions, the film’s electrical, optical and structural properties were measured by using UV-VIS-NIR spectrophotometer, photoluminescence(PL), Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Hall’s measurement. Finally, based on the investigation results, the film’s properties were identified and discussed.