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1
Harrison, Dale A. "Photoluminescence spectroscopy of D§- states in GaAs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0006/NQ37711.pdf.
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Dybiec, Maciej. "Spatially resolved photoluminescence spectroscopy of quantum dots." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001767.
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McGhee, Ewan James. "The photoluminescence spectroscopy of single quantum dots." Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/1116.
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Thảo. "Photoluminescence spectroscopy on erbium-doped and porous silicon." Amsterdam : Amsterdam : [s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/83659.
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Tsagli, Kelvin Xorla. "Temperature Dependence of Photoluminescence Spectra in Polystyrene." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1625744248503334.
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Amloy, Supaluck. "Polarization-resolved photoluminescence spectroscopy of III-nitride quantum dots." Doctoral thesis, Linköpings universitet, Halvledarmaterial, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-87748.
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In this thesis, results from studies on (In)GaN quantum dots (QDs) are presented, including investigations of the structural, optical and electronic properties. The experimental studies were performed on GaN and InGaN QDs grown by molecular beam epitaxy, taking advantage of the Stranki-Krastanov growth mode for the GaN QD samples and the composition segregation for the InGaN QD samples. Optical spectroscopy of the (In)GaN QDs was performed with a combination of different experimental techniques, e.g. stationary microphotoluminescence (μPL) and timeresolved μPL. The μPL spectroscopy is suitable for studies of single QDs due to the wellfocused excitation laser spot, and it typically does not require any special sample preparation. The powerful combination of power and polarization dependences was used to distinguish the exciton and the biexciton emissions from other emission lines in the recorded spectra. The QDs could be observed with random in-plane anisotropy, as determined by the strong linear polarization for single QDs but with different angular orientation from dot to dot. Additionally, these experimental results are in good agreement with the computational results revealing a similar degree of polarization for the exciton and the biexciton emissions. Further, the theory predicts that the discrepancy of the polarization degree is larger between the positive and negative trions in comparison with the exciton and the biexciton. Based on this result, polarization resolved spectroscopy is proposed as a simple tool for the identification of trions and their charge states. The fine-structure splitting (FSS) and the biexciton binding energy (Ebxx) are essential QD parameters of relevance for the possible generation of quantum entangled photon pairs in a cascade recombination of the biexciton. In general, the Coulomb interaction between the negatively charged electron and the positively charged hole lifts the fourfold degeneracy of the electron and hole pair ground state, forming a set of zero-dimensional exciton states of unequal energies. This Coulomb-induced splitting, referred to as the FSS, results in an electronic fine structure, which is strongly dependent on the symmetry of the exciton wave function. The FSS was in this work resolved and investigated for excitons in InGaN QDs, using polarization-sensitive μPL spectroscopy employed on the cleaved-edge of the samples. As expected, the FSS is found to exhibit identical magnitudes, but with reversed sign for the exciton and the biexciton. For quantum information applications, a vanishing FSS is required, since otherwise the emissions of the polarization-entangled photon pairs in the cascade biexciton recombination will be prohibited. The biexcitons are found to exhibit both positive and negative binding energies for the investigated QDs. Since a negative binding energy indicates a repulsive Coulomb interaction, such biexcitons (or exciton complexes) cannot exist in structures of higher dimensionality. On the other hand, a biexciton with a negative binding energy can be found in QDs, since the exciton complexes still remain bound due to their three dimensional confinement. Moreover, the biexciton binding energy depends on the dot size, which implies that a careful size control of dots could enable manipulation of the biexciton binding energy. A large Ebxx value enables better and cheaper spectral filtering, in order to purify the single photon emission, while a proposed time reordering scheme relies on zero Ebxx for the generation of entangled photons. The dynamics of the exciton and the biexciton emissions from InGaN QD were measured by means of time-resolved μPL. The lifetimes of the exciton related emissions are demonstrated to depend on the dot size. Both the exciton and the biexciton emissions reveal mono-exponential decays, with a biexciton lifetime, which is about two times shorter than the exciton lifetime. This implies that the QD is small, with a size comparable to the exciton Bohr radius. The photon generation rates can be manipulated by controlling the QDs size, which in turn can be utilized for generation of single- and entangled-photons on demand, with a potential for applications in e.g. quantum information. The polarization of the emitted single photons can be manipulated by using a polarizer, but to the prize of photon loss and reduced emission intensity. Alternative methods to control the polarization of the emission light are a manipulation of the dot symmetry statically by its shape or dynamically by an externally applied electric field. Predictions based on performed calculations show that in materials with a small spin-orbit split-off energy (ΔSO), like the III-nitride materials, the polarization degree of the emission is more sensitive to dot asymmetry than in materials with a large value for ΔSO, e.g. the III-arsenide materials. Moreover, for an electric field applied in the 1͞10 and the 11͞2 directions of the zinc-blende lens-shaped QDs grown on the (111) plane, the polarization degree of InN QDs is found to be significantly more, by a factor of ~50 times, sensitive to the electric field than for GaN QDs. This work demonstrates that especially the InN based QD, are suitable for manipulation of the polarization by the direct control of the dot symmetry or by externally applied electric fields.
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Karlberg, Thomas Andre. "Optical Studies of Single Semiconductor Nanowires by Micro-Photoluminescence Spectroscopy." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11147.
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Over the recent years semiconductor nanowires have gained much attention for their potential to either improve existing technology or create novel devices. This potential has been realized in devices such as semiconductor nanowire lasers[2-3] and nanowire single-photon detectors[4]. With nanowire technology it could be possible to create single-photon nanowire lasers that emit photons in the near infrared region. Such devices should prove very interesting for telecommunications and quantum cryptography.The purpose of this master thesis was the study of the optical properties of GaAs nanowires with GaAsSb inserts. For this reason, both nanowires with and without an AlGaAs coating to increase the nanowire Quantum Efficiency (QE) have been subjected to low temperature PL spectroscopy. In an attempt to determine the physical origin of the different optical properties of different nanowires, µ-PL spectroscopy, Scanning Transmission Electron Microscopy (STEM) and Transmission Electron Microscopy (TEM) was carried out on the same nanowires of a sample with AlGaAs shell nanowires. Through these measurements, it was found that STEM at 30 kV did not change the optical properties of the nanowire, but 200 kV TEM had a detrimental effect on nanowire PL. Through the structurally and optically correlated examination, it was found that stacking faults near the insert was not the origin of the power dependent behavior of the insert emission, and in combination with PL measurements of both zincblende (ZB) and wurtzite (WZ) GaAs nanowires the electronic band structure of the nanowire inserts was determined to very likely be type-II. Also, a theoretical explanation of the origin of the observed insert emission behavior was presented, and polarization dependent PL measurements were presented and discussed.
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Filippov, Stanislav. "Micro-photoluminescence and micro-Raman spectroscopy of novel semiconductor nanostructures." Doctoral thesis, Linköpings universitet, Funktionella elektroniska material, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-123939.
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Low-dimensional semiconductor structures, such as one-dimensional nanowires (NWs) and zerodimensional quantum dots (QDs), are materials with novel fundamental physical properties and a great potential for a wide range of nanoscale device applications. Here, especially promising are direct bandgap II-VI and III-V compounds and related alloys with a broad selection of compositions and band structures. For examples, NWs based on dilute nitride alloys, i.e. GaNAs and GaNP, provide both an optical active medium and well-shaped cavity and, therefore, can be used in a variety of advanced optoelectronic devices including intermediate band solar cells and efficient light-emitters. Self-assembled InAs QDs formed in the GaAs matrix are proposed as building blocks for entangled photon sources for quantum cryptography and quantum information processing as well as for spin light emitting devices. ZnO NWs can be utilized in a variety of applications including efficient UV lasers and gas sensors. In order to fully explore advantages of nanostructured materials, their electronic properties and lattice structure need to be comprehensively characterized and fully understood, which is not yet achieved in the case of aforementioned material systems. The research work presented this thesis addresses a selection of open issues via comprehensive optical characterization of individual nanostructures using micro-Raman ( -Raman) and micro-photoluminescence ( -PL) spectroscopies. In paper 1 we study polarization properties of individual GaNP and GaP/GaNP core/shell NWs using polarization resolved μ-PL spectroscopy. Near band-edge emission in these structures is found to be strongly polarized (up to 60% at 150K) in the orthogonal direction to the NW axis, in spite of their zinc blende (ZB) structure. This polarization response, which is unusual for ZB NWs, is attributed to the local strain in the vicinity of the N-related centers participating in the radiative recombination and to their preferential alignment along the growth direction, presumably caused by the presence of planar defects. Our findings therefore show that defect engineering via alloying with nitrogen provides an additional degree of freedom to control the polarization anisotropy of III-V nanowires, advantageous for their applications as a nanoscale source of polarized light. Structural and optical properties of novel coaxial GaAs/Ga(N)As NWs grown on Si substrates, were evaluated in papers 2-4. In paper 2 we show by using -Raman spectroscopy that, though nitrogen incorporation shortens a phonon correlation length, the GaNAs shell with [N]<0.6% has a low degree of alloy disorder and weak residual strain. Additionally, Raman scattering by the GaAs-like and GaNlike phonons is found to be enhanced when the excitation energy approaches the E+ transition energy. This effect was attributed the involvement of intermediate states that were created by N-related clusters in proximity to the E+ subband. Recombination processes in these structures were studied in paper 3 by means of μ-PL, μ-PL excitation (μ-PLE), and time-resolved PL spectroscopies. At low temperatures, the alloy disorder is found to localize photo-excited carriers leading to predominance of localized exciton (LE) transitions in the PL spectra. Some of the local fluctuations in N composition are suggested to create three-dimensional confining potentials equivalent to that for QDs, based on the observation of sharp PL lines within the LE contour. In paper 4 we show that the formation of these QD-like confinement potentials is somewhat facilitated in spatial regions of the NWs with a high density of structural defects, based on correlative spatially-resolved structural and optical studies. It is also concluded the principal axis of these QD-like local potentials is mainly oriented along the growth direction and emit light that is linearly polarized in the direction orthogonal to the NW axis. At room temperature, the PL emission is found to be dominated by recombination of free carriers/excitons and their lifetime is governed by non-radiative recombination via surface states. The surface recombination is found to become less severe upon N incorporation due to N-induced modification of the surface states, possibly due to partial surface nitridation. All these findings suggest that the GaNAs/GaAs hetero-structures with the onedimensional geometry are promising for fabrication of novel optoelectronic devices on foreign substrates (e.g. Si). Fine-structure splitting (FSS) of excitons in semiconductor nanostructures has significant implications in photon entanglement, relevant to quantum information technology and spintronics. In paper 5 we study FSS in various laterally-arranged single quantum molecular structures (QMSs), including double QDs (DQDs), quantum rings (QRs), and QD-clusters (QCs), by means of polarization resolved μ-PL spectroscopy. It is found that FSS strongly depends on the geometric arrangements of the QMSs, which can effectively tune the degree of asymmetry in the lateral confinement potential of the excitons and can reduce FSS even in a strained QD system to a limit similar to strain-free QDs. Fabrication of nanostructured ZnO-based devices involves, as a compulsory step, deposition of thin metallic layers. In paper 6 we investigate impact of metallization by Ni on structural quality of ZnO NWs by means of Raman spectroscopy. We show that Ni coating of ZnO NWs causes passivation of surface states responsible for the enhanced intensity of the A1(LO) in the bare ZnO NWs. From the resonant Raman studies, strong enhancement of the multiline Raman signal involving A1(LO) in the ZnO/Ni NWs is revealed and is attributed to the combined effects of the Fröhlich interaction and plasmonic coupling. The latter effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for utilizing such structures as efficient nano-sized gas sensors.
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Mellor, Ian. "Isotopic oxygen exchange reactions on magnesium oxide." Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298901.
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Pemasiri, Karunananda. "Investigation of zincblende, wurtzite, and mixed phase InP nanowires by photocurrent, photoluminescence and time-resolved photoluminescence spectroscopies." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377873494.
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Gulla, Stian. "Advanced Micro Photoluminescence Spectroscopy of Single GaAs/AlGaAs Core-Shell Nanowires." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22788.
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Self-catalyzed (SC) growth is a relatively new approach to growing GaAs nanowires (NWs). It has several advantages to Au-catalyzed growth, such as integration on Si platforms. Many of the growth parameters, including growth rate and V/III ratio, and their influence on the growth process, are not fully understood. Three samples of SC GaAs/AlGaAs core-shell NWs were grown with different V/III ratios (17.4, 23.8 and 30.1), in order to study how this parameter influences the optoelectronic properties of the NWs. The molecular beam epitaxy vapor-liquid-solid approach was used to grow the samples. In this work they were investigated with excitation power-, temperature-, polarization- and time-resolved micro photoluminescence (u-PL) spectroscopy.Only the sample of highest V/III ratio, sample "sigma", exhibited free exciton emission coming from zinc blende (ZB) GaAs in the core of the NWs. The other two samples were dominated by type-II transitions, likely originating from the tip regions with interchanging ZB-wurtzite (WZ) layers. Sigma-NWs appear to have defects, however, as shown by its low emission intensity at room temperature. A reference sample, sample "alpha", was also studied with the same methods. This sample, which was grown with a medium V/III ratio (20.0), but a lower growth rate, also showed signs of free exciton emission, possibly originating from WZ regions in the tip.It is concluded that a higher V/III ratio is beneficial to optoelectronic applications, and that the number of defects are lowered, mostlikely due to fewer Ga antisites in the core. It is proposed that samples sigma and alpha are studied by high-resolution transmission electron microscopy(HR-TEM) to further determine their structure. Also, new samples should be grown with higher V/III ratios, some of which should have a lower growth rate. Efforts to passivate the defect-rich tip from the core, such as axial AlGaAs inserts, are proposed.
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Wang, Kai. "Micro-Photoluminescence Spectroscopy of Semiconductor Quantum Dots in the Telecom Regime." Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279446.
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Eggleston, James Michael. "Optical spectroscopy of thin film semiconductor structures." Thesis, Durham University, 1997. http://etheses.dur.ac.uk/4769/.
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This thesis consists of a study of several thin film semiconductor structures of practical technological use either presently or in the near future. The first system studied is an ultra thin film single crystal gallium arsenide layer. The absorption spectra of these layers are measured and transitions at both the F- point and L-point of the Brillouin Zone are observed, the latter are not normally measurable in thicker layers. The observed shift in the F-point absorption edge is attributed to contributions from the Franz-Keldysh Effect and the Moss-Burstein Effect. The temperature dependence of the L-point energy gap is measured and compared with previous data. The next system investigated is an n-type porous silicon layer coated with p-type polyaniline. Both photoluminescence and electroluminescence spectra and the electrical characteristics have been measured for this system. The interface between the two layers is found to be a rectifying junction consistent with a potential barrier formed at the interface. In forward bias, it is possible to generate electroluminescence in the visible and near infra red regions. The final structure studied is a thin film cadmium sulphide-cadmium telluride solar cell structure. The cells are found to have a low efficiency of around 1% as grown, but a process of treatment with cadmium chloride and annealing in air improves this by a factor of approximately ten. Photoluminescence measurements on the back surface of the cadmium telluride revealed three major emission bands at 1.59 eV, 1.55 eV and 1.45 eV. By varying temperature and incident laser power, attempts at assigning the bands to specific impurity centres in the cadmium telluride is made Using a novel bevelling etch technique to prepare samples, depth dependent measurement of the photoluminescence is possible. This reveals that the major changes associated with the improvement in efficiencies occurs at the interface between the CdS and the CdTe.
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Hoang, Thang Ba. "Investigation of Single Semiconductor Nanowire Heterostructures Using Polarized Imaging Spectroscopy." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1206034605.
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Dijksman, Arjen Toni. "Spectroscopy of colloidal quantum dots of controlled shape and size." Paris 6, 2013. http://www.theses.fr/2013PA066459.
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Colloidal semiconductor nanocrystals, also called quantum dots, show properties of absorption and luminescence that find practical applications, such as biomedical imaging, light-emitting diodes and photovoltaics. In this thesis, we have synthesized CdSe quantum dots of different sizes and have improved their luminescent properties by growing a thick shell of CdS. We characterized these core-shell CdSe/CdS quantum dots with confocal fluorescence microscopy, correlating their photoluminescence with their cathodoluminescence and with their transmission electron microscopy images. This correlation was used to determine that the photoluminescence energy corresponds to the cathodoluminescence energy. We propose a model that describes the electron’s path in a nanocrystal. This results in a linear equation that relates the energy of excitonic transitions to the size of the nanocrystal. This equation takes into account a phase jump and a time delay that corresponds to the electron bouncing at the surface. Probing this equation with experimental data reveals remarkable invariants that indicate that it can be applied to various materials in the 1D, 2D and 3D strong quantum confinement rangeLes nanocristaux semi-conducteurs colloïdaux, aussi dénommés boîtes quantiques colloïdales, présentent des propriétés d'absorption et de luminescence qui peuvent trouver des applications pratiques, par exemple dans l'imagerie biomédicale, dans les diodes électroluminescentes et dans le photovoltaïque. Dans cette thèse, nous nous sommes intéressés à synthétiser des nanocristaux CdSe de différentes tailles et à améliorer leurs propriétés de luminescence par la croissance d'une coque épaisse de CdS. Nous avons caractérisé ces nanocristaux coeur-coque CdSe/CdS en microscopie confocale de fluorescence, en corrélant la photoluminescence des mêmes nanocristaux uniques en cathodoluminescence et en imagerie de microscopie électronique à transmission. Cette corrélation a permis de déterminer que l'énergie de photoluminescence de ces nanocristaux correspond à celle de cathodoluminescence. A partir d'une modélisation du chemin de l'électron dans le nanocristal, nous proposons une relation qui relie l'énergie des transitions excitoniques à sa taille, de façon linéaire. Cette relation tient compte d'un saut de phase et d'un délai qui correspondent à l'électron rebondissant à la surface. La confrontation de cette relation aux données expérimentales fait ressortir des invariants remarquables qui indiquent que cette relation est transposable à plusieurs matériaux en confinement quantique fort 1D, 2D et 3D
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Heitmann, Filip August. "Zinc Oxide Nanolaser : Photoluminescence spectroscopy and optical pumping of zinc oxide nanowires." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16785.
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This Master's thesis is a continuation of the specialization project I did during the spring of 2011. The goal of said project was to set up a system for UV-photoluminescence experiments in the Nanophotonics laboratory at the Department of Electronics and Telecommunications at NTNU, and conduct photoluminescence spectroscopy measurements on different zinc oxide nanostructures, including GaAs/AlGaAs/ZnO core/multishell nanowires. This thesis involves studying zinc oxide nanowires using both a continuous wave and pulsed ultraviolet laser light, and the final goal is to optically excite these nanowires so they achieve lasing. Using a Tsunami Ti:sapph mode-locked tunable laser and a flexible harmonic generator, laser pulses with a pulse duration of 2 ps could be generated at wavelengths around 300 nm, at a power of around 5 mW. At this power, some of the wires showed possible signs of optical gain, but since it was not possible to apply more power to the wires, this could not be confirmed. If there had be enough time, both low temperature measurements and time-resolved spectroscopy, using a streak camera, would have been performed.
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Hayes, Gary Robert. "Ultrafast relaxation processes in semiconductors studied by femtosecond time-resolved photoluminescence spectroscopy." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263051.
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Böttner, Stefan. "Rolled-Up Vertical Microcavities Studied by Evanescent Wave Coupling and Photoluminescence Spectroscopy." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-166810.
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Vertically rolled-up microcavities are fabricated using differentially strained nanomembranes by employing rate and temperature gradients during electron beam evaporation of SiO2. The geometry of the rolled-up tubes is defined by a photo-lithographically patterned polymer sacrificial layer beneath the SiO2 layers that is dissolved to start the rolling. Rolled-up tubes support resonances formed by constructive interference of light propagating along the circumference. Optical studies are performed in the visible spectral range using a micro-photoluminescence (µPL) setup to excite and detect optical modes. Record high quality factors (Q factors) of 5400 for rolled-up resonators probed in PL-emission mode are found and their limits are theoretically investigated. Axial modes can also be supported when an increased winding number in the center is realized by appropriate pattern designs. In addition, higher order radial modes can be confined when atomic layer deposition (ALD) coatings are applied. Both types of modes are identified using polarization and spatially resolved µPL maps.
Evanescent-wave coupling by tapered fibers and tubes on substrates is the second method used to study light confinement and to demonstrate frequency filtering in ALD coated rolled-up microcavities. Scans are performed by monitoring light from a tunable laser in the range of 1520-1570 nm after transmission through the tapered fiber. Dips in the spectrum are found and attributed to fundamental and axial resonant modes. Moreover, by coupling two tapered fibers to a lifted rolled-up microcavity, a four-port add-drop filter is demonstrated as a future component for vertical resonant light transfer in on-chip optical networks.
Simulations show that the subwavelength tube wall thickness limits the Q factor at infrared wavelengths and ALD coatings are necessary to enhance the light confinement. After coating, two linear polarization states are found in experiment and fundamental and axial modes can be selectively excited by coupling the fiber to different positions along the tube axis. Spatially and polarization resolved transmission maps reveal a polarization dependent axial mode distribution which is verified theoretically.
The results of this thesis are important for lab-on-chip applications where rolled-up microcavities are employed as high resolution optofluidic sensors as well as for future uses as waveguide coupled components in three-dimensional multi-level optical data processing units to provide resonant interlayer signal transfer.
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Herz, Laura Maria. "Aggregation effects in conjugated polymer films studied by time-resolved photoluminescence spectroscopy." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620191.
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Rablău, Corneliu Ioan. "Photoluminescence and optical absorption spectroscopy of infrared materials Cr²+:ZnSe and ZnGeP₂." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1124.
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Thesis (Ph. D.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xv, 200 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 194-200).
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Meenakarn, Chanchana. "A TEM investigation of atomic ordering in AlGaInP epilayers grown on GaAs (001) by gas-source MBE." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324981.
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Avramenko, K. A., A. S. Romanyuk, N. N. Roshina, V. V. Strelchuk, O. F. Kolomys, L. V. Zavyalova, S. V. Svechnikov, and B. A. Snopok. "Raman and Photoluminescence Study of ZnO Films Grown by Chemical Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35010.
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In this paper phonon and emission properties of ZnO films grown by metalorganic chemical vapour
deposition (MOCVD) at ambient pressure and by molecular beam epitaxy (MBE) are investigated using
Raman and photoluminescence (PL) spectroscopy. It is shown that high-frequency shift of non-polar phonon
modes corresponds to elastic compressive strain in the plane parallel to c-axis and is equal to 3.2×10−3
and 2.2×10−3 for ZnO film grown by MOCVD and MBE, respectively. The possibility of obtaining highquality
ZnO films grown by MOCVD was demonstrated.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35010
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Chornokur, Ganna. "Photoluminescence spectroscopy of bioconjugated quantum dots and their application for early cancer detection." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002801.
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Bilgi, Seda. "Photoluminescence Study Of Ge-implanted Gase And Inse Single Crystals Grown By Bridgman Method." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607482/index.pdf.
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In this study, photoluminescence properties of as grown, Ge implanted GaSe and InSe crystals with doses 1013, 1014, and 1015 ions/cm2 and 1015 ions/cm2 Ge implanted and annealed GaSe and InSe single crystals grown by using 3-zone vertical Bridgman-Stockbarger system have been studied by photoluminescence spectroscopy (PL). PL spectra of as grown and implanted GaSe samples with three different doses have been studied in the ranges within the wavelength interval 570-850 nm and in the temperature ranges between 21 and 110 K. Temperature dependencies of all observed bands revealed that the peak with highest energy has excitonic origin and most of the others originate from donor-acceptor pair recombination. For GaSe samples implanted with 1013 and 1015 ions/cm2 Ge, PL spectra exhibited four emission bands while for as grown and the sample implanted with 1014 ions/cm2
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Ge had three bands. Variations of emission peaks were studied as a function of temperature. It was observed that centers of all bands shifted towards red continuously with temperature. The intensities of the emission peaks showed similarities with those obtained from as grown, 1013 and 1014 ions/cm2 Ge implanted GaSe while the peak intensities of the sample implanted with 1015 ions/cm2 Ge decreased with the temperature continuously. Using the temperature variation of the peak intensities and peak energy values activation energies were obtained and these results revealed that the two bands with low wavelength to be excitonic origin for the implanted samples with the doses 1013 and 1015 ions/cm2 Ge. Similar results were obtained for the implanted with 1015 ions/cm2 Ge and annealed sample. The other two peaks observed for these samples were attributed to donor acceptor pair transitions. In addition, direct band gaps were found to be 2.12 eV at 32 K for as grown, 2.121 eV at 25 K for 1013 ions/cm2 Ge implanted, 2.121 eV at 21 K for 1014 ions/cm2 Ge implanted, 2.124 eV at 33 K for 1015 ions/cm2 Ge implanted GaSe samples and lastly 2.113 eV at 28 K for 1015 ions/cm2 Ge implanted and annealed GaSe. PL spectra of as grown, 1013, 1014, 1015 ions/cm2 Ge implanted, and 1015 ion/cm2 Ge implanted and annealed InSe samples were also obtained at 20 K. Two broad bands were observed in the spectrum of all InSe crystals and considered to be due to impurity levels within the materials.
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Aouadi, Mohamed-Samir. "Sputter-deposition of epitaxial CdTe and PbTe layers plasma emission spectroscopy of the discharge and photoluminescence spectroscopy of the layers." Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5530.
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Seyhan, Ayse. "Photoluminescence Properties Of Si Nanocrystals Embedded In Sio2 Matrix." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611750/index.pdf.
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This thesis examines the luminescence properties of nanoscale silicon (Si) by
using spectroscopic techniques. Since the development of new optical devices
requires understanding light emission mechanism optical spectroscopy has
become more important tool in the analysis of these structures. In this thesis, Si
nanocrystals embedded in SiO2 matrix will be studied.
Photoluminescence (PL) and Time-resolved photoluminescence spectroscopy
(TRPL) have been used to detect the light emission in UV-Vis-NIR range.
Experiments have been performed in the temperature range 10-300 K. PL is
sensitive to impurities and defects that affect materials quality and device
performance. In this context, the role of defects in limiting the luminescence of Si
nanocrystals and the removal of these defects by hydrogen passivation has been
investigated.
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TRPL was employed to determine the time evolution of photoluminescence as
function of temperature. The decay time of the PL spectra was determined by a
stretched exponential function and perfectly fitted to an expression based on three
excitonic levels. Carrier lifetimes associated with these three levels were
determined and compared with literature.
Additionally, temporal variation of PL from free-standing Si nanoparticles is
studied under a strong laser illumination. The observed bleaching behavior (time
dependent emission intensity), which is reversible, have discussed in terms of
exciton trapping at the interface between nanocrystal and the surrounding oxide
layer.
The results of this thesis will provide new insight on the understanding of light
emission mechanism of Si nanocrytals.
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Xie, Xing. "Optical properties of ZnO thin film : raman spectroscopy, optical reflection, photoluminescence and stimulated emission /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202005%20XIE.
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Mjåland, Terje Sund. "Micro-photoluminescence spectroscopy of self-catalyzed zincblende GaAs nanowires grown by molecular beam epitaxy." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19066.
Full textAbstract:
In this thesis, single zincblende GaAs nanowires grown by molecular beam epitaxy using the self-catalyzed approach were studied with m-photoluminescence spectroscopy in order to assess the optical quality of self-catalyzed GaAs nanowires grown for the first time at NTNU and to compare the optical properties of self-catalyzed GaAs nanowires with Au-assisted GaAs nanowires and bulk GaAs references. The low temperature and temperaturedependence measurements revealed type II recombinations between zincblende and wurtzite segments occurring at the nanowire tips, however it was established that radiative recombination does not take place in the zincblende GaAs nanowire core. As the thesis progressed, valuable feedback was given to the growers in order to optimize nanowire growth conditions. The thesis builds upon data from earlier work within this project andprovides a foundation for future work on self-catalyzed GaAs nanowire devices at NTNU.
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Brar, Jamie. "Photoluminescence Spectroscopy of CdSe/Cd[0.5]Zn[0.5]S Core/Shell Colloidal Quantum Dots." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20089.
Full textAbstract:
The photoluminescence (PL) of dense aggregates of CdSe/Cd0.5Zn0.5S core/shell colloidal quantum dots (cQDs) was investigated to gain insight into bleaching processes, quantum efficiency behaviour, band gap energy temperature dependence, and the phonon-coupling contribution to thermal broadening. This work also encompassed a study of various sample preparation techniques. These newly investigated strain-engineered core/shell cQDs, having an effective lattice constant in between that of CdS and ZnS, fosters the study of novel properties not present in the previous two systems. The bleaching behaviour, studied subject to strong optical pumping for different external cQD environments, showed effective shell passivation, thus limiting non-radiative processes mainly to the core or shell structures. The relative quantum efficiency was determined as a function of temperature, showing two distinct regimes, with activation of a phonon process above ~ 180 K. The band gap energy was found to follow the empirical Varshni relation describing the temperature dependence of a semiconductor material, dominating any thermally induced changes of the cQD volume and confinement potential. The PL spectral width change with temperature showed highly coupled carrier-phonon scattering behaviour.
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Wahl, Markus Solberg. "Micro-Photoluminescence Spectroscopy of Au-assisted MBE Grown AlGaAs Nanowires with Axial GaAs Inserts." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19338.
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AlGaAs nanowires (NWs) with axial GaAs inserts, grown with molecular beam epitaxy will be investigated with micro-photoluminescence spectroscopy, including CW and pulsed excitation at cryogenic and ambient temperatures.
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Laura, M. Robinson. "USING TIME-RESOLVED PHOTOLUMINESCENCE SPECTROSCOPY TO EXAMINE EXCITON DYNAMICS IN II-VI SEMICONDUCTOR NANOSTRUCTURES." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin980259259.
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Colombier, Léo. "Spectroscopie optique de nanotubes de carbone : complexes excitoniques et cavités plasmoniques." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20058/document.
Full textAbstract:
Cette thèse porte d'une part sur l'étude de la stabilité du biexciton dans le nanotube de carbone et, d'autre part, sur le contrôle de l'émission du nanotube par le couplage des nanotubes de carbone à des antennes plasmoniques. La technique de spectroscopie optique non-linéaire de saturation d'absorption, appliquée aux nanotubes de carbone, nous a permis d'effectuer la première observation du biexciton dans cette nanostructure. Plus précisément, deux raies d'absorptions induites sont observées et attribuées au trion et à l'exciton par des études en températures et en puissance du laser de pompe. La mise en oeuvre d'une configuration à trois faisceaux basée sur un schéma en double-pompe permet de confirmer la photo-génération du biexciton en tant qu'excitation élémentaire du nanotube de carbone. Le biexciton est observé avec une énergie de liaison de 107 ± 1 meV pour la chiralité (9,7) et présente un profil asymétrique de Fano. Une première estimation de la dynamique de recombinaisondu biexciton est donnée par description quantitative du processus de Fano. Le modèle est basé sur le formalisme de la susceptibilité non-linéaire du troisième ordre χ(3) incluant le couplage coulombien entre le biexciton et le continuum des paires électron-trou de la première singularité de Van Hove. Le facteur de Fano est évaluée à q = 5 et conduit à l'estimation du taux de recombinaison Auger du biexciton B ∈ [0.1; 1] μm·ps−1 . Le rendement radiatif du biexciton est ainsi estimé à 10−6 .Dans le but d'étudier les nanotubes en cavité plasmonique, une expérience de micro-photoluminescence et une expérience de spectroscopie en champ sombre, sont développés dans le domaine spectrale des télécommunications (1.3 μm et 1.55 μm). La caractérisation de divers types échantillons de nanotube et des antennes plasmoniques sont présentés. Des résultats préliminaires sur un échantillon de nanotubes associés dans une configuration patch à des antennes plasmoniques montrent une corrélation entre la position des antennes et les zones luminescentes, ainsi qu'un changement de l'allure des spectres de photoluminescence. Ces premiers résultats constituent une transition dans la démarche de notre projet. L'étape de calibration des expériences est en phase de finition et l'étude des propriétés physique des nanotubes en cavité plasmonique représente désormais une activité opérationnelle au sein de notre équipeThis thesis focus on both the biexciton's stability in carbon nanotubes, and the control of the nanotube emission through its coupling to plasmonic antenna.We report the first observation of biexciton in carbon nanotubes by means of spectral holeburning nonlinear optical spectroscopy. More precisely, two induced absorption lines are detected and assigned to trion and biexciton after investigation of their temperature and pump power dependences. An additional proof of the detection of the biexciton, as an elementary excitation of carbonnanotubes, is given in a three-beam configuration based on a two-pump scheme. The biexciton of the (9,7) chirality is observed with a binding energy of 107 ± 1 meV and shows an asymetric Fano lineshape. A first estimation of the biexciton's recombinaison dynamics is given by the quantitative analysis of the nonlinear signal. Our analytic model is formulated in the framework of the chi(3) nonlinear response, including coulomb interaction between biexcitons and free electron-hole pairs lying in the first Van Hove singularity. A Fano factor of about q = 5 is determined, which drives us to the estimation of biexciton's Auger recombinaison rate B ∈ [0.1; 1] μm · ps−1 . The Biexciton's radiative yield is then estimated of the order of 10−6 .In order to study nanotubes in plasmonic cavities, we developed micro-photoluminescence and dark-field spectroscopy experiments in the optical fiber telecommunication wavelengths (1.3 μm and 1.55 μm). Caracterisation of nanotube samples and plasmonic antenna are presented. Preliminary results on nanotubes inserted in a patch antenna have shown correlation between antenna's position and the spatial distribution of luminescence. Moreover, a change in the carbon nanotube's photoluminescence profile is observed. These results appear to be a turning point in our work. The calibration of our experiment is at its end and studies of optical properties of carbon nanotubes coupled to plasmonic antenna are now on stream in our team
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Federspiel, Francois. "Etude optique du transfert d'énergie entre une nanostructure semiconductrice unique et un feuillet de graphène." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE015/document.
Full textAbstract:
Mes travaux de thèse portent sur l’interaction de type FRET (tranfert d’énergie résonant de Förster) entre une nanostructure semiconductrice colloïdale individuelle et le graphène. La première partie concerne l’établissement de la théorie du FRET et ce pour plusieurs types de nanostructures. Vient ensuite la partie expérimentale, à commencer par le montage optique ainsi que les méthodes d’analyse, tant pour la spectroscopie que pour la photoluminescence. Par la suite, nous décrivons les résultats obtenus pour divers types de nanocristaux sphériques en interaction directe avec le graphène (incluant des multicouches) : le transfert d’énergie a des effets drastiques sur la photoluminescence mais aussi sur le clignotement des nanocristaux. Puis nous étudions la dépendance du FRET avec la distance ; dans le cas des boîtes quantiques, nous observons une loi en 1/z^4. Par contre, dans le cas de nanoplaquettes, la fonction est plus complexe et dépend de la températureMy PhD subject is the FRET interaction (Förster-like resonant energy transfer) between single colloidal semiconductor nanostructures and graphene. The first part is about the development of the interaction theory with the graphene for several types of nanostructures. Then comes the experimental part, and firstly the optical setup together with the analysis methods, for both spectroscopy and photoluminescence. After that, we describe our results about different types of spherical nanocrystals directly interacting with graphene (which can be multilayer) : the energy transfer has a huge effect on the photoluminescence, as well as the blinking behaviour of the nanocrystals. Then we measure the dependency of the energy transfer as a function the distance ; in the case of quantum dots, we observe a 1/z^4 law. On another hand, in the case of nanoplatelets, the function is more complex and depends on the temperature
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Chanda, Sashi Kumar. "INVESTIGATION OF DEFECTS IN N-TYPE 4H-SIC AND SEMI-INSULATING 6H-SIC USING PHOTOLUMINESCENCE SPECTROSCOPY." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07072005-102232/.
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Photoluminescence spectroscopy is one of the most efficient and sensitive non-contact techniques used to investigate defects in SiC. In this work, room temperature photoluminescence mapping is employed to identify different defects that influence material properties. The correlation of the distribution of these defects in n-type 4H-SiC substrates with electronic properties of SiC revealed connection between the deep levels acting as efficient recombination centers and doping in the substrate. Since deep levels are known to act as minority carrier lifetime killers, the obtained knowledge may contribute to our ability to control important characteristics such as minority carrier lifetime in SiC. In semi-insulating (SI) 6H-SiC, the correlation between room temperature infrared photoluminescence maps and the resistivity maps is used to identify deep defects responsible for semi-insulating behavior of the material. Different defects were found to be important in different families of SI SiC substrates, with often more than one type of defect playing a significant role. The obtained knowledge is expected to enhance the yield of SI SiC fabrication and the homogeneity of the resistivity distribution across the area of large SiC substrates.
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Rowland, Gareth Llywelyn. "Photomodulated reflectance spectroscopy of novel semiconductor materials." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/843223/.
Full textAbstract:
Room temperature photomodulated reflectance (PR), Photoluminescence (PL) and double crystal x-ray diffraction (DCXRD) measurements have been performed on a series of tensilely strained InxGa1-xAs (0.316 ≤ x ≤ 0.533) multiple quantum well (QW) structures, with In0.80Ga0.20As0.43P0.57 barriers. The DCXRD measurements provided accurate information on composition, strain and layer thickness, while PR was used to determine the energies of the full manifold of allowed and forbidden critical point interband QW transitions. A three-band effective mass formalism was used to model the QW transitions to derive structural information on each sample. The energies of the ground-state QW transitions, H11 and L11, were found to increase with tensile strain, becoming degenerate near 0.36% tensile strain. Room temperature PR and conventional reflectance (R) measurement have been performed on two I.R. emitting InGaAs/GaAs/A1As vertical cavity surface emitting laser (VCSEL) structures. The R measurements were modelled using a transfer matrix formalism to determine errors in the growth fluxes. A new PR lineshape model has been developed based on energy dependent Seraphin coefficients, to describe the cavity mode interaction with a confined-state QW transition. The model is demonstrated on a set of PR spectra, and used in a novel way to derive the Deltaepsilon2 spectrum of the QW layers directly. The results are compared with those taken of the QW layers directly after removing the top Bragg stack reflector. Whilst the QW layers in one sample were found to be close to nominal, the in composition of QW in the other sample was found to depart significantly from the nominal 23%, and was found to be 28%. Room temperature and ~ 80K PR measurements were performed on three InAs/GaAs self-assembled quantum dot (QD) structures: a sample with a single layer of QDs, and two with two layers. The PR revealed five equally spaced confined-state QD transitions, at both 80K and room temperature, with ~ 54 meV separation. The behaviour of the QD1 transition as a function of temperature was investigated and an anomalous increase in linewidth was observed on cooling. Annealing of one of the samples produced a strong blue shift (~ 250 meV) and narrowing of the QD transitions.
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Issac, Abey. "Photoluminescence Intermittency of Semiconductor Quantum Dots in Dielectric Environments." Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601267.
Full textAbstract:
The experimental studies presented in this thesis deal with the photoluminescence intermittency of semiconductor quantum dots in different dielectric environments. Detailed analysis of intermittency statistics from single capped CdSe/ZnS, uncapped CdSe and water dispersed CdSe/ZnS QDs in different matrices provide experimental evidence for the model of photoionization with a charge ejected into the surrounding matrix as the source of PL intermittency phenomenon. The distribution of the dark state lifetimes can be described by a power law over a wide range while that of bright state can be described by a power law at shorter times followed by an exponential decay. The lifetimes of the bright and dark states are influenced by the dielectric properties of the surrounding environment. Our experimental results show that the lifetime of the dark state increases with the dielectric constant of the matrix. This is very clear from the linear correlation between αoff and f (ε). We propose a self-trapping model to explain the increase of dark state lifetimes with the dielectric constant of the matrix. A charge will be more stabilized in a medium with high dielectric constant. An energetically more favourable state for an electron in a high dielectric medium decreases the return probability which eventually increases the duration of the off-time. Moreover, the self-trapping model establishes a general model for distribution of states in a matrix. We like to mention, that in the case of bright states, a qualitative observation is the cross over of the on-time power law behavior to an exponential one. The power law part of the decay is nearly matrix independent while the exponential decay, which limits the maximum on-time, strongly depends on dielectric properties of the environment. The exponential part of the on-time probability decays much faster in a high dielectric medium and there exists a linear relation between the time constant of the exponential decay and f (ε). Theoretical background has been provided for the observed results using the recently published DCET model which correlates PL intermittency of QDs with properties of the environment. This supports our previous conjecture of a general model for matrix controlled blinking process. The disagreement between experimentally observed dependence of αoff and f (ε) for different matrices with that of the static tunnelling model proposed by Verberk is due to the fact that the tunneling model considers only an electron transfer between a QD and spatially distributed trap states in vacuum. These states are already stabilized states. It does not assume any medium in between. Therefore, matrix dependent blinking kinetics can not be explained quantitatively by tunneling model even though tunneling between a QD and spatially distributed trap states gives a power law distribution for the blinking kinetics. DCET is a more general (dynamic) model. The bright and dark state parabolas contain QD, charge and the matrix. Therefore, this model could in principle explain matrix dependent blinking kinetics in a better way, for example, the energy difference between the minima of the bright and dark state parabolas (-ΔG0) is defined by the stabilization energy of the system provided by the matrix. However, due to lack of the relevant intrinsic parameters we did not compare this relationship and dependence qualitativelyBetrachtet man die Fluoreszenz einzelner Farbstoffmoleküle oder Halbleiternanokristalle bei kontinuierlicher Anregung, so stellt man fest, dass die im Zeitverlauf beobachtete Intensität einer stochastischen Variation unterliegt, d. h. dass das Chromophor zwischen emittierenden und nicht emittierenden Zuständen, auch Hell- und Dunkelzuständen genannt, hin- und herschaltet. Dieses als Blinken bekannte Phänomen ist physikalisch wie auch technologisch herausfordernd, lässt es doch einerseits die Realisierbarkeit einer Reihe von quantenoptischen Anwendungen, so z. B. auf dem Gebiet der Quantenkryptographie, dem Quantum Computing oder der optischen Schaltungstechnik auf Basis einzelner Quantenobjekte, in naher Zukunft möglich erscheinen. Andererseits setzt es gewissen Anwendungen, die auf die permanente Sichtbarkeit des Chromophors aufbauen, Grenzen, so zum Beispiel der Verwendung als Lumineszenzmarker in der medizinischen Diagnostik. Weiterhin ist festzustellen, dass das Blinken kritisch von den äußeren Bedingungen und von den Umgebungsparametern abhängt. Aus diesen und anderen Gründen ist ein fundamentales Verständnis der physikalischen Ursachen und der Wechselwirkungsprozesse unerlässlich. Die Forschung dazu steckt noch in den Kinderschuhen. Basierend auf umfangreiche Messungen der Fluoreszenzzeitreihen einzelner Nanokristalle aus CdSe und CdSe/ZnS in verschiedenen Umgebungen, zeigt diese Dissertation exemplarisch den Einfluss der Dielektrizitätsparameter auf das Blinken. Zur Erklärung des Sachverhalts wird ein so genanntes Self-Trapping-Modell zu Rate gezogen. Demnach kommt es zu einer Ionisation des Quantenobjekts und anschließender Ladungstrennung, woraufhin die abgetrennte Ladung für eine gewisse Zeit in der Umgebung lokalisiert bleibt. Die Dauer der Lokalisierung und damit der emittierenden und nicht emittierenden Perioden hängt von der dielektrischen Funktion des umgebenden Materials ab. Dies ist als direkter Nachweis für den photoinduzierten Ladungstransfer als Ursache des Fluoreszenzblinkens zu deuten. Die Arbeit demonstriert, dass die experimentellen Zeitreihen die charakteristischen Merkmale eines diffusionsgesteuerten Ladungstransferprozesses besitzen und nimmt dabei den gegenwärtigen wissenschaftlichen Diskurs über geeignete theoretische Modelle des Fluoreszenzblinkens auf
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Dai, Xuemin, and 戴學敏. "Experimental and theoretical studies of defects related emissions in ZnO crystals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B4163388X.
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Dai, Xuemin. "Experimental and theoretical studies of defects related emissions in ZnO crystals." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B4163388X.
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Wen, Xiaoming, and n/a. "Ultrafast spectroscopy of semiconductor nanostructures." Swinburne University of Technology, 2007. http://adt.lib.swin.edu.au./public/adt-VSWT20070426.110438.
Full textAbstract:
Semiconductor nanostructures exhibit many remarkable electronic and optical properties.
The key to designing and utilising semiconductor quantum structures is a physical understanding
of the detailed excitation, transport and energy relaxation processes. Thus the nonequilibrium
dynamics of semiconductor quantum structures have attracted extensive attention in recent years.
Ultrafast spectroscopy has proven to be a versatile and powerful tool for investigating transient
phenomena related to the relaxation and transport dynamics in semiconductors.
In this thesis, we report investigations into the electronic and optical properties of various
semiconductor quantum systems using a variety of ultrafast techniques, including up-conversion
photoluminescence, pump-probe, photon echoes and four-wave mixing. The semiconductor
quantum systems studied include ZnO/ZnMgO multiple quantum wells with oxygen ion
implantation, InGaAs/GaAs self-assembled quantum dots with different doping, InGaAs/InP
quantum wells with proton implantation, and silicon quantum dots. The spectra of these
semiconductor nanostructures range from the ultraviolet region, through the visible, to the
infrared. In the UV region we investigate excitons, biexcitons and oxygen implantation effects in
ZnO/ZnMgO multi-quantum wells using four-wave mixing, pump-probe and photoluminescence
techniques. Using time-resolved up-conversion photoluminescence, we investigate the relaxation
dynamics and state filling effect in InGaAs self-assembled quantum dots with different doping,
and the implantation effect in InGaAs/InP quantum wells. Finally, we study the optical properties
of silicon quantum dots using time-resolved photoluminescence and photon echo spectroscopy on
various time scales, ranging from microseconds to femtoseconds.
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He, Shijiang. "Near infrared photoelasticity of polycrystalline silicon and it's relation to in-plane residual stresses." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-08052005-121255/.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Sergei Ostapenko, Committee Member ; Shreyes N. Melkote, Committee Member ; Ajeet Rohatgi, Committee Member ; Jianmin Qu, Committee Member ; I. Charles Ume, Committee Member ; Steven Danyluk, Committee Chair. Vita. Includes bibliographical references.
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Bieker, Steffen [Verfasser], and Wolfgang [Gutachter] Ossau. "Time and Spatially Resolved Photoluminescence Spectroscopy of Hot Excitons in Gallium Arsenide / Steffen Bieker. Gutachter: Wolfgang Ossau." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1112041168/34.
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Wotherspoon, Alex. "An investigation of electron irradiated type IIa and N-doped CVD diamonds by microscopic photoluminescence (PL) spectroscopy." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288449.
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Furkert, Suzanne. "An investigation of electron irradiation and implantation damage centres in silicon carbide by microscopic photoluminescence (PL) spectroscopy." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409832.
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Evans, Geraint Andrew. "Characterisation of point defects in SiC by microscopic optical spectroscopy." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391196.
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Songprakob, Wantana. "Optical studies of highly-doped GaAs:C." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28927.
Full textAbstract:
Infrared reflectivity and transmittance measurements (200=5000 cm^-1) were carried
out on heavily-doped GaAs:C films grown by molecular beam epitaxy. With increasing
carbon concentration, a broad reflectivity minimum develops in the
1000=3000 cm^-1 region and the one-phonon band near 270 cm^-1 rides on a progressively increasing
high-reflectivity background. An effective-plasmon/one-phonon dielectric
function with only two free parameters (plasma frequency Ï p and damping constant
γp) gives a good description of the main features of the reflectivity spectra. The
dependence of effective plasma frequency on hole concentration p is linear. At each doping, the effective-plasmon damping
constant is large and corresponds to an optical hole mobility that is about half the
Hall mobility at that p. Secondary-ion mass spectroscopy and localized-vibrational-mode
measurements indicate that the Hall-effect-derived hole concentration is close
to the carbon concentration and that the Hall factor is close to unity, so that the Hall
mobility provides a good estimate of the actual dc mobility. Also, analysis shows that,
for our highly-doped samples, the observed dichotomy between the dc and infrared
mobilities is not a statistical-averaging artifact of the approximations involved in the
model. The explanation of the small infrared mobility resides in the influence of
intervalence band absorption on the effective-plasmon fit, which operationally defines
that mobility via the effective-plasmon damping.
The optical properties obtained with the use of the effective-plasmon model for
GaAs:C yield a phenomenological, approximate, overall picture of the infrared spectra.
But the neglect of intervalenceband transitions, for this p-type semiconductor,
is shown (in this dissertation) to be a serious drawback of this simple model. In
order to obtain the optical properties of GaAs:C in a model-independent way, and to
attempt to resolve the apparent dc/infrared mobility dichotomy, we made use of a
recently-developed spectroscopic-analysis procedure. Using direct numerical-solution
techniques for the reflectance (R) and transmittance (T) equations of a multilayer
structure, we analyzed our infrared R and T results for highly-doped films having
hole concentrations from 2Ã 10^19 up to 1.4Ã 10^20 cm^-3. The optical properties were
determined for photon energies from 0.07 to 0.6 eV, in which region plasmon (intraband)
and intervalenceband contributions are in competition. Our results for the
optical absorption coefficient resolve two separate peaks located (at high doping) at
about 0.1 and 0.2 eV. (The effective-plasmon model necessarily missed the two-peak
character of the actual absorption spectrum.)
By carrying out theoretical calculations of the intervalenceband (IVB) absorption
processes for our dopings, we identify the peak near 0.2 eV with light-hole
to heavy-hole IVB transitions, and we attribute the lower-energy peak to the hole
plasmon. Our experimental absorption spectra are very well described by a model
combining the intervalenceband contribution to the dielectric function with a plasmon
contribution. The hole-plasmon parameters omega_plasmon and gamma_plasmon that we obtain
for highly-doped p-GaAs yield an infrared mobility which (unlike the too-small IVB-entangled
infrared mobility implied by the use of the usual effective-plasmon model)
is in substantial agreement with the dc mobility. Therefore, in actuality, there is no
dc/infrared mobility discrepancy. The discrepancy implied by the use of the usual,
standard-operating-procedure, effective-plasmon model is a consequence of the inadequacy
of that model for p-type semiconductors exhibiting intervalenceband infrared
absorption.
Raman-scattering measurements were carried out on the GaAs:C films. Only the
phononlike coupled plasmon-phonon mode is observed. The non-occurrence of the
plasmonlike mode is due to the large damping of the hole plasmon and the competition
with strong Raman scattering by intervalenceband transitions among the
heavy-hole, light-hole, and split-off bands. Analysis of the phononlike coupled mode,
within the framework of the wavevector-dependent Lindhard-Mermin dielectric function,
supports the hole properties that we determined by Hall and infrared studies.
Photoluminescence measurements showed that the split-off band also participates in
the photoluminescence of GaAs:C, giving rise to an above-bandgap emission band
corresponding to transitions from the conduction band to the split-off valence band.Ph. D.
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Wang, Dake Park Minseo. "Optical spectroscopy of wide-band-gap semiconductors raman and photoluminescence of gallium nitride, zinc oxide and their nanostructures /." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Fall/Dissertations/WANG_DAKE_24.pdf.
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Sedhain, Ashok. "Optical properties of ALN and deep UV photonic structures studied by photoluminescence." Diss., Kansas State University, 2011. http://hdl.handle.net/2097/8522.
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Doctor of PhilosophyDepartment of Physics
Jingyu Lin
Time-resolved deep ultraviolet (DUV) Photoluminescence (PL) spectroscopy system has been employed to systematically monitor crystalline quality, identify the defects and impurities, and investigate the light emission mechanism in III-nitride semiconducting materials and photonic structures. A time correlated single photon counting system and streak camera with corresponding time resolutions of 20 and 2 ps, respectively, were utilized to study the carrier excitation and recombination dynamics. A closed cycle He-flow cryogenic system was employed for temperature dependent measurements. This system is able to handle sample temperatures in a wide range (from 10 to 900 K). Structural, electrical, and morphological properties of the material were monitored by x-ray diffraction (XRD), Hall-effect measurement, and atomic force microscopy (AFM), respectively. Most of the samples studied here were synthesized in our laboratory by metal organic chemical vapor deposition (MOCVD). Some samples were bulk AlN synthesized by our collaborators, which were also employed as substrates for homoepilayer growth. High quality AlN epilayers with (0002) XRD linewidth as narrow as 50 arcsec and screw type dislocation density as low as 5x10[superscript]6 cm[superscript]-2 were grown on sapphire substrates. Free exciton transitions related to all valence bands (A, B, and C) were observed in AlN directly by PL, which allowed the evaluation of crystal field (Δ[subscript]CF) and spin-orbit (Δ[subscript]SO) splitting parameters exerimentally. Large negative Δ[subscript]CF and, consequently, the difficulties of light extraction from AlN and Al-rich AlGaN based emitters due to their unique optical polarization properties have been further confirmed with these new experimental data. Due to the ionic nature of III-nitrides, exciton-LO phonon Frohlich interaction is strong in these materials, which is manifested by the appearance of phonon replicas accompanying the excitonic emission lines in their PL spectra. The strength of the exciton-phonon interactions in AlN has been investigated by measuring the Huang-Rhys factor. It compares the intensity of the zero phonon (exciton emission) line relative to its phonon replica. AlN bulk single crystals, being promising native substrate for growing nitride based high quality device structures with much lower dislocation densities (<10[superscript]4 cm[superscript]-2), are also expected to be transparent in visible to UV region. However, available bulk AlN crystals always appear with an undesirable yellow or dark color. The mechanism of such undesired coloration has been investigated. MOCVD was utilized to deposit ~0.5 μm thick AlN layer on top of bulk crystal. The band gap of strain free AlN homoepilayers was 6.100 eV, which is ~30 meV lower compared to hetero-epitaxial layers on sapphire possessing compressive strain. Impurity incorporation was much lower in non-polar m-plane growth mode and the detected PL signal at 10 K was about an order of magnitude higher from a-plane homo-epilayers compared to that from polar c-plane epilayers. The feasibility of using Be as an alternate p-type dopant in AlN has been studied. Preliminary studies indicate that the Be acceptor level in AlN is ~330 meV, which is about 200 meV shallower than the Mg level in AlN. Understanding the optical and electronic properties of native point defects is the key to achieving good quality material and improving overall device performance. A more complete picture of optical transitions in AlN and GaN has been reported, which supplements the understanding of impurity transitions in AlGaN alloys described in previous reports.
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Yeo, Inah. "A quantum dot in a photonic wire : spectroscopy and optomechanics." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY076/document.
Full textAbstract:
Dans cette thèse, nous avons étudié les propriétés optiques de boîtes quantiques InAs/GaAs contenues dans un fil photonique. Des résultats antérieurs à cette thèse ont montré que ces fils photoniques permettent d’extraire les photons avec une efficacité très élevée.Le premier résultat original de ce travail est l’observation de la dérive temporelle de la raie d’émission de la photoluminescence d’une boîte quantique. Cet effet a été attribué à la lente modification de la charge de surface du fil due à l’absorption des molécules d’oxygène présentes dans le vide résiduel du cryostat. Nous avons montré qu’une fine couche de Si3N4 permettait de supprimer cette dérive. La dérive temporelle pouvant être différente pour différentes boites quantiques, nous avons pu tirer partie de cet effet pour mettre en résonance deux boites quantiques contenues dans le même fil.Le deuxième résultat original est la mise en évidence de la modification de l’énergie d’émission d’une boîte quantique soumise à une contrainte mécanique induite par la vibration du fil. Nous avons observé que le spectre de la raie d’émission d’une boîte quantique s’élargit considérablement lorsque le fil est mécaniquement excité à sa fréquence de résonance. A l’aide d’une illumination stroboscopique synchronisée avec l’excitation mécanique, nous avons pu reconstruire l’évolution du spectre d’une boîte quantique au cours d’une période de la vibration mécanique. L’amplitude de l’oscillation spectrale de la raie de luminescence dépend de la position de la boîte dans le fil à cause d’un très fort gradient de contrainte. En utilisant deux modes d’oscillation mécanique de polarisations linéaires et orthogonales, nous pouvons extraire une cartographie complète de la position des boîtes quantiques à l’intérieur du fil. Enfin, grâce à ce gradient, on peut, dans certains cas, trouver une position du fil pour laquelle deux boites quantiques peuvent être amenées en résonanceIn the framework of this thesis, single InAs/GaAs quantum dot devices were studied by optical means. Starting with a general description of self-assembled InAs QDs, two types of single QD devices were presented. The first approach was a tapered GaAs photonic wire embedding single InAs QDs whose efficiency as a single photon source was previously shown to be 90%. We investigated several optical properties of the single QDs. The charged and neutral states of the QD were identified and selectively excited using quasi-resonant excitation.The first original result of this thesis is the observation of a continuous temporal blue-drift of the QD emission energy. We attributed this blue drift to oxygen adsorption onto the sidewall of the wire, which modified the surface charge and hence the electric field seen by the QD. Moreover, we demonstrated that a proper coating of the GaAs photonic nanowire surface suppressed the drift. The temperature effect on this phenomenon revealed an adsorption peak around 20K, which corresponds to the adsorption of oxygen on GaAs. This observation is in good agreement with previous temperature studies with a tapered photonic wire. This was the first study of the spectral stability of photonic wires embedding QDs, crucial for resonant quantum optics experiments. As an alternative, we took advantage of this temporal drift to tune QD emission energies. In a controlled way, we tuned into resonance two different QDs which were embedded in the same photonic nanowire. In the last part of this work, we studied the influence of the stress on single QDs contained in a trumpet-like GaAs photonic wire. The main effect of stress is to shift the luminescence lines of a QD. We applied the stress by exciting mechanical vibration modes of the wire. When the wire is driven at its the mechanical resonance the time-integrated photoluminescence spectrum is broaden up to 1 meV owing to the oscillating stress, The measured spectral modulation is a first signature of strain-mediated coupling between a mechanical resonator and embedded QD single light emitter. With a stroboscopic technique, we isolated a certain phase of the oscillating wire and thereby selected a value of QD emission energies. As a highlight of our study, we managed to bring two different QDs contained in the same wire into resonance by controlling their relative phase. In addition, we could extract the 2D spatial positioning of embedded QDs from the spectral shifts observed for two orthogonal mechanical polarizations.. The investigation of the strain-mediated tuning of QDs can, therefore, be an effective tool to explore the QD positions without destroying the sample
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Tainter, Gregory Demaray. "Spatially resolved charge transport and recombination in metal-halide perovskite films and solar cells." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/286026.
Full textAbstract:
Metal-halide perovskites show great promise as solution-processable semiconductors for efficient solar cells and LEDs. In particular, the diffusion range of photogenerated carriers is unexpectedly long and the luminescence yield is remarkably high. While much effort has been made to improve device performance, the barriers to improving charge transport and recombination properties remain unidentified. I first explore charge transport by investigating a back-contact architecture for measurement. In collaboration with the Snaith group at Oxford, we develop a new architecture to isolate charge carriers. We prepare thin films of perovskite semiconductors over laterally-separated electron- and hole-selective materials of SnOₓ and NiOₓ, respectively. Upon illumination, electrons (holes) generated over SnOₓ (NiOₓ) rapidly transfer to the buried collection electrode, leaving holes (electrons) to diffuse laterally as majority carriers in the perovskite layer. We characterise charge transport parameters of electrons and holes, separately, and demonstrate that grain boundaries do not prevent charge transport. Our results show that the low mobilities found in applied-field techniques do not reflect charge diffusivity in perovskite solar cells at operating conditions. We then use the back-contact architecture to investigate recombination under large excess of one charge carrier type. Recombination velocities under these conditions are found to be below 2 cm s⁻¹, approaching values of high quality silicon and an order of magnitude lower than under common bipolar conditions. Similarly, diffusion lengths of electrons and holes exceed 12 μm, an order of magnitude higher than reported in perovskite devices to date. We report back-contact solar cells with short-circuit currents as high as 18.4 mA cm⁻², giving 70% external charge-collection efficiency. We then explore the behaviour of charge carriers in continuously illuminated metal-halide perovskite devices. We show that continuous illumination of perovskite devices gives rise to a segregated charge carrier population, and we find that the distance photo-induced charges travel increases significantly under these conditions. Finally, we examine intermittancy in the photoluminescence intensity of metal-halide perovskite films.
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Venturi, Linda. "Etude des propriétés de photoluminescence de nano-matériaux sous champ électrique intense." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR118.
Full textAbstract:
Dans cette thèse, la tomographie à sonde atomique assistée par laser est couplée in situ à un banc de photoluminescence (PL), où le rayonnement laser pulsé est utilize pour déclencher l’évaporation ionique des échantillons et, simultanément, pour activer l’émission à partir des centres optiquement actifs présents dans le matériau. Pour ce travail, deux matériaux différents ont été sélectionnés : des nano-aiguilles de diamant avec des défauts optiquement actifs intégrés (centres de couleur) et une hétérostructure multi-quantique (MQW) ZnO / (Mg, Zn)O, qui contient des émetteurs quantiques d’épaisseurs différentes. Grâce à cette configuration originale de photoluminescence, l’influence du champ électrique sur la structure fine de certains centres de couleur, noyés dans les nano-aiguilles de diamant, a été observée. La première étude s’est concentrée sur le centre neutre de vacance d’azote (NV0), qui est l’un des centres de couleur les plus étudiés dans la littérature. L’évolution de la signature optique NV0, en fonction du biais appliqué, a permis d’évaluer la contrainte mécanique (> 1 GPa) et le champ électrique agissant sur les pointes de diamant. Ces résultats démontrent une nouvelle méthode originale pour effectuer la piezo-spectroscopie sans contact des systems nanométriques sous une contrainte de traction uniaxiale, générée par le champ électrique. Cette méthode a également été appliquée à un autre centre de couleur, dont la nature n’est toujours pas claire dans la littérature, émettant à 2,65 eV, et plus sensible que les centres de couleur NV0 au champ de contrainte / déformation. Des nouveaux résultats sur ses propriétés opto-mécaniques ont été obtenus, mais son identité reste à comprendre. Le champ d’évaporation du diamant étant très élevé, les nano-aiguilles de diamant n’ont pas été analysées à l’aide de La-APT. Par conséquent, la technique couplée in situ a été appliquée afin d’étudier l’hétérostructure ZnO / (Mg, Zn) O MQW, en accédant à la structure, à la composition et à la signature optique de l’échantillon sondé dans une seule expérience. Les spectres de photoluminescence acquis par le spécimen au cours de son évaporation en cours représentent une source unique d’informations pour la compréhension du mécanisme de l’interaction lumière-matière et la physique de la photoémission sous champ électrique élevé. La corrélation des informations structurelles et optiques, liées à cette hétérostructure MQW, démontre que la technique couplée in situ peut chevaucher la limite de diffraction du laser PL et que, comme pour les nano-aiguilles de diamant, il est possible d’estimer le stress de traction induit. Les résultats obtenus par couplage in situ de la technique La-APT avec la spectroscopie PL montrent qu’un tel instrument est une technique innovante et puissante pour effectuer des recherches à l’échelle nanométrique. Pour cette raison, ce travail peut ouvrir de nouvelles perspectives pour une compréhension approfondie de la physique liée aux systèmes étudiés en parallèle avec l’amélioration continue de la configuration expérimentaleIn this thesis, the Laser-assisted Atom Probe Tomography is coupled in-situ with a photoluminescence (PL) bench, where the pulsed laser radiation is used to trigger the ion evaporation from the specimens and, simultaneously, to activate the emission from optically active centers present into the material. For this work, two different materials were selected: diamond nano-needles with embed- ded optically active defects (color centers) and a ZnO/(Mg,Zn)O multi-quantum-well (MQW) heterostructure, which contains quantum emitters of different thicknesses. Thanks to this original photoluminescence setup, the influence of the electric field on the fine structure of some color centers, embedded into the diamond nanoneedles, was observed. The first study focused on the neutral nitrogen-vacancy center (NV0), which is one among the most studied color centers in literature. The evolution of the NV0 optical signature, as a function of the applied bias, allowed to evaluate the mechanical stress (> 1 GPa) and the electric-field acting on diamond tips. These results demon- strate an original new method to perform contactless piezo-spectroscopy of nanoscale systems under uniaxial tensile stress, generated by the electric field. This method was applied also on another color center, which nature is still not clear in literature, emitting at 2.65 eV, and more sensitive than the NV0 color centers to the stress/strain field. New results on its opto-mechanical properties were obtained, but its identity still needs to be understood. Since the evaporation field of diamond is really high, the diamond nanoneedles were not analyzed using La-APT. Therefore the coupled in-situ technique was applied in order to study the ZnO/(Mg,Zn)O MQW heterostructure, accessing to the structure, composition and optical signature of the probed specimen in only one experiment. The photoluminescence spectra acquired by the specimen during its ongoing evaporation represents a unique source of information for the understanding of the mechanism of light-matter interaction and the physics of photoemission under high electric field. The correlation of the structural and optical information, related to this MQW heterostructure, demonstrates that the coupled in-situ technique can overlap the diffraction limit of the PL laser and that, as done for the diamond nanoneedles, is pos- sible to estimate the induced-tensile-stress. The results achieved by the in-situ coupling of the La-APT technique with the PL spec- troscopy show that such instrument is an innovative and powerful technique to perform research at the nanometric scale. For this reason, this work can open new perspectives for a deeply understanding of the physicics related to the studied systems in parallel with the continuous enhancement of the experimental setup