Dissertations / Theses on the topic 'Photoluminescence'
To see the other types of publications on this topic, follow the link: Photoluminescence.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Photoluminescence.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Chiu, Sheng-Kuei. "Photoluminescent Silicon Nanoparticles: Fluorescent Cellular Imaging Applications and Photoluminescence (PL) Behavior Study." PDXScholar, 2015. http://pdxscholar.library.pdx.edu/open_access_etds/2455.
Full textAbstract:
Molecular fluorophores and semiconductor quantum dots (QDs) have been used as cellular imaging agents for biomedical research, but each class has challenges associated with their use, including poor photostability or toxicity. Silicon is a semiconductor material that is inexpensive and relatively environmental benign in comparison to heavy metal-containing quantum dots. Thus, red-emitting silicon nanoparticles (Si NPs) are desirable to prepare for cellular imaging application to be used in place of more toxic QDs. However, Si NPs currently suffer poorly understood photoinstability, and furthermore, the origin of the PL remains under debate.
This dissertation first describes the use of diatomaceous earth as a new precursor for the synthesis of photoluminescent Si NPs. Second, the stabilization of red PL from Si NPs in aqueous solution via micellar encapsulation is reported. Thirdly, red to blue PL conversion of decane-terminated Si NPs in alcohol dispersions is described and the origins (i.e., color centers) of the emission events were studied with a comprehensive characterization suite including FT-IR, UV-vis, photoluminescence excitation, and time-resolved photoluminescence spectroscopies in order to determine size or chemical changes underlying the PL color change. In this study, the red and blue PL was determined to result from intrinsic and surface states, respectively.
Lastly, we determined that the blue emission band assigned to a surface state can be introduced by base addition in originally red-emitting silicon nanoparticles, and that red PL can be restored by subsequent acid addition. This experimentally demonstrates blue PL is surface state related and can overcome the intrinsic state related excitonic recombination pathway in red PL event. Based on all the data collected and analyzed, we present a simple energy level diagram detailing the multiple origins of Si NP PL, which are related to both size and surface chemistry.
2
Vijh, Uma Parvathy. "Photoluminescence by Interstellar Dust." See Full Text at OhioLINK ETD Center (Requires Adobe Acrobat Reader for viewing), 2005. http://www.ohiolink.edu/etd/view.cgi?toledo1122478565.
Full textAbstract:
Thesis (Ph.D.)--University of Toledo, 2005.Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Physics." Bibliography; leaves 209-225.
3
Al-Ajili, Adwan Nayef Hameed. "Photoluminescence of nanostructured silicon." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/26999.
Full textAbstract:
The photoluminescence (PL) emitted by porous silicon has been investigated under different conditions of excitation using a pulsed nitrogen laser source, and the continuous tunable DV synchrotron source at Daresbury Laboratory. The project involved sample preparation, and PL measurements using a custom-built optical laser-based system for lifetime measurements. This in itself necessitated software and hardware development to enable interfacing and data-logging using an IBM-compatible PC. The equipment development formed a major part of the project.
4
Xiao, Bin, and 肖斌. "Photoluminescence study of ZnO materials." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47153593.
Full textAbstract:
Zinc oxide (ZnO) is a wide band gap (3.4eV at 300K) II-VI semiconductor with an exciton binding energy up to 60meV and is promising in the realization of excitonic or polaritonic lasing effect. Photoluminescence is widely used in studying the band gap and defect levels of ZnO. However, understanding in defects of ZnO is still far from satisfaction and remains controversial. Different authors suggest different explanations and mechanisms.
In the present study we investigate in the photoluminescence spectra of four kinds of ZnO single crystal, namely as-grown (not implanted) Zn-face polished, Zn-implanted, O-implanted and He-implanted. The samples are annealed both in air and argon gas at a temperature of 350, 650, 750, 900 and 1200oC. The results show that O-implanted sample is weaker in excitonic emission and has an annealing effect tendency not consistent with that of Zn-implanted and He-implanted. Ion implantation would introduce defects in favor of yellow luminescence and the defects would anneal out gradually as the annealing temperature is rising.published_or_final_version
Physics
Master
Master of Philosophy
5
Alrrshedan, Marrwa. "Photoluminescence from Bulk GaN Substrates." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2802.
Full textAbstract:
Photoluminescence (PL) has been studied from different types of bulk GaN samples grown by hydride vapor phase epitaxy technique at Kyma Technologies. Point defects in bulk and at the surface affect the electrical and optical properties of GaN and could be analyzed by PL. The surface of the samples was polished with different techniques: one is chemical mechanical polish (CMP) and another is mechanical polish (MP). PL data from MP and CMP surfaces show that PL intensity from the CMP-treated surface is much higher than that from the MP-treated surface. This can be explained by defects formed during the process of MP polish. However, after the MP-treated surface is etched with RIE method, the optical quality of the MP-treated surface improves. In particular, as the depth of etching increases from 50 nm to 700 nm, the PL intensity increases by a factor of 1000. PL from the CMP surfaces of undoped bulk GaN samples contains a broad red luminescence (RL) band and a broad green luminescence (GL) band. However, PL from the CMP surfaces of Fe-doped GaN samples contained a blue luminescence band (labeled as BL2 in literature) and the yellow luminescence (YL) band. PL from MP-treated surfaces (both undoped and Fe-doped) was very weak and it contained relatively narrow red and green bands. These bands, labeled RL2 and GL2, respectively, are quenched at relatively low temperatures, in contrast to the RL and GL bands which are almost independent of temperature in the range from 15 to 300 K.
6
Zheng, Wan Hua. "Photoluminescence study of porous silicon." HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/138.
Full text
7
Ngan, Mei Lun. "Photoluminescence excitation of porous silicon." HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/139.
Full text
8
Faklaris, Orestis. "Photoluminescent diamond nanoparticles as labels in cells : study of their optical properties and investigation of their cellular uptake mechanism." Cachan, Ecole normale supérieure, 2009. http://tel.archives-ouvertes.fr/tel-00439561/fr/.
Full textAbstract:
Ce travail de thèse porte sur l'utilisation des NanoDiamants Photoluminescents (NDPs) pour des applications en bio-imagerie. Les nanodiamants (NDs) sont photoluminescents grâce à la présence de centres colorés azote-lacune (NV) dans leur maille cristalline. Le manuscrit est divisé en deux parties. La première concerne l'étude des propriétés optiques des centres colorés NV dans des NDs. Après l'optimisation de la concentration des centres NV, nous comparons la photoluminescence des NDPs à celle des nanoparticules semi-conductrices commerciales; nous concluons qu'elle peut être équivalente, même supérieure dans le cas des NDPs. Pour augmenter le contraste d'imagerie intracellulaire des NDPs, nous avons étudié l'excitation à 2-photons des centres NV. Lors de cette étude avec un laser impulsionnel, nous avons découvert que le signal de photoluminescence des NDPs excité à un photon chute très fortement lorsque l'impulsion infrarouge est simultanée de l'excitation visible. Nous avons étudié la façon d'utiliser cet effet pour l'imagerie de super-resolution. La deuxième partie porte sur l'étude des applications des NDPs comme sondes pour la bio-imagerie. Dans le but d'utiliser des NDPs comme véhicules de biomolécules, nous avons étudié leurs mécanismes d'internalisation et avons élucidé leur localisation intracellulaire, en inhibant des voies différentes d'internalisation et par des expériences d'immunofluorescence. De plus, nous avons montré que les NDPs ne sont pas toxiques pour des cellules en culture. Un premier essai de vectorisation a été mené avec de NDPs couverts d'ADN plasmidiqueThis thesis work studies the use of Photoluminescent NanoDiamonds (PNDs) for bio-imaging applications. Nanodiamonds are photoluminescent thanks to embedded nitrogen-vacancy (NV) color centers. The thesis is divided in two parts. The first part concerns the study of the optical properties of NV color centers in nanodiamonds. After optimization of the NV center concentration, we compared the photoluminescence of PNDs to commercial Quantum Dots (QDs) and conclude that it can be similar or even higher in the case of PNDs. To enhance the imaging contrast of internalized by cells PNDs, we studied the 2-photon excitation properties of NV centers. While implementing a pulsed excitation laser, we discovered that simultaneous one- and two-photon excitation (IR+VIS pulses) quenches the photoluminescence signal of PNDs. We examined how this effect can serve for super-resolution imaging of NV color centers in nanodiamonds. The second part of the work is devoted to the applications of PNDs as bio-imaging probes. In the prospect of applications of PNDs as drug delivery vehicles, we studied the uptake mechanisms of PNDs and elucidated their intracellular localization by blocking different entry mechanisms and by immunofluorescence experiments. Moreover, we ensured that PNDs are not toxic for cells in culture. As a first try of vectorization we covered PNDs with plasmid DNA and examined the transfection efficiency
9
Wilde, Fabian. "Unidirectional photoluminescence emission of pierced microdisks /." München : Dr. Hut Verlag, 2009. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=017120456&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Full text
10
Seyhan, Ayse. "Photoluminescence Specroscopy Of Cds And Gase." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1258383/index.pdf.
Full textAbstract:
With the use of photoluminescence (PL) spectroscopy one can able to get a
great deal of information about electronic structure and optical processes in
semiconductors by the aid of optical characterization. Among various compound
semiconductors, Cadmium Sulfide (CdS) and Gallium Selenide (GaSe) are
interesting materials for their PL emissions. Particularly, due to its strong anisotropy,
investigation of GaSe necessitates new experimental approaches to the PL technique.
We have designed, fabricated and used new experimental set-up for this purpose.
In this thesis, we have investigated the PL spectra of both CdS and GaSe as a
function of temperature. We observed interesting features in these samples. These
features were analyzed experimentally and described by taking the band structure of
the crystals into account. From the excitonic emissions, we determined the bandgap
energy of both materials. We studied various peaks that appear in the PL spectra and their origin in the material. We have found that donor acceptor transitions are
effective in CdS at low temperatures. A transition giving rise to a red emission was
observed and attributed to a donor level which is likely to result form an S vacancy
in CdS crystal. The PL peaks with energy close to the bandgap were observed in
GaSe. These peak were attributed to the bound excitons connected either to the direct
or indirect band edge of GaSe. The striking experimental finding in this work was the
PL spectra of GaSe measured in different angular position with respect to the crystal
axis. We observed that PL spectra exhibit substantial differences when the angular
position of the laser beam and the detector is changed. The optical anisotropy which
is responsible for these differences was measured experimentally and discussed by
considering the selection rules of the band states of GaSe.
11
Ratmann, Cristiane Wienke Raubach. "Metal sulfides: photoluminescence and photocatalytic properties." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/6279.
Full textAbstract:
Made available in DSpace on 2016-06-02T20:34:46Z (GMT). No. of bitstreams: 1
5401.pdf: 5113907 bytes, checksum: bc63a1e068663b50eac2b2108398f3f0 (MD5)
Previous issue date: 2013-08-30Universidade Federal de Minas Gerais
In this work we report an experimental and theoretical study of photoluminescence (PL) and photocatalytic activity of pure metal sulfides and systems furnished prepared by microwave assisted solvothermal (MAS) method. The theoretical model of the decorated system was created in order to analyze the electronic transition, especially in their interfaces. The results show that the system interface decorated (core-shell) produces an electron charge transfer of holes from cadmium sulfide (CdS) to zinc sulfide (ZnS), which helps increase the PL and photocatalytic activity of the system. For the pure systems, was observed the efficacy of the method synthesis employed verified that the process for obtaining the ZnS and calcium sulfide (CaS) was extremely important. Through the theoretical models was possible to evaluate the influence caused by the solvothermal influence caused by the MAS method. The variation in the synthesis parameters shows a direct influence on the PL properties of sulfides obtained which can be attributed to structural organization. The theoretical results how this order and disorder of the system can affect these properties of the obtained materials.
Neste trabalho relata-se um estudo teórico e experimental da atividade fotoluminescente (FL) e fotocatalítica de sulfetos metálicos puros e em sistemas decorados preparados por intermédio do método solvotérmico assistido por micro-ondas. O modelo teórico do sistema decorado foi criado de forma a analisar a transição eletrônica, principalmente nas suas interfaces. Os resultados mostram que a interface do sistema decorado (core-shell) produz uma transferência de carga do elétron do sulfeto de cádmio (CdS) para os buracos do sulfeto de zinco (ZnS), o que ajuda a aumentar a atividade fotoluminescente e fotocatalítica do sistema. Para os sistemas puros, observou-se a eficácia do método de síntese empregado, sendo verificado que o processo de obtenção do ZnS e sulfeto de cálcio (CaS) foi de extrema importância. Por intermédio dos modelos teóricos foi possível avaliar a influência causada pelo método. A variação nos parâmetros de síntese mostra uma influência direta nas propriedades FL dos sulfetos obtidos que pode ser atribuída a organização estrutural. O modelo teórico mostra como essa ordem e desordem do sistema podem afetar essas propriedades dos materiais obtidos.
12
Mosor, Sorin. "Photoluminescence of Quantum Confined Semiconductor Structures." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1309%5F1%5Fm.pdf&type=application/pdf.
Full text
13
Makuc, Boris. "Photoluminescence of ZnSe grown by MOVPE." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61819.
Full text
14
Gower, Joanne Elizabeth. "Photoluminescence of point defects in silicon." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300758.
Full text
15
Sun, Ye. "Synthesis and photoluminescence of ZnO nanostructures." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440141.
Full text
16
House, Jody L. (Jody Lee) 1970. "Optical characterization of ZnSe by photoluminescence." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36430.
Full text
17
Wilkinson, Victoria Ailsa. "High pressure photoluminescence of semiconductor structures." Thesis, University of Surrey, 1990. http://epubs.surrey.ac.uk/844514/.
Full textAbstract:
High pressure photoluminescence has been used to study semiconductor structures. The measurements have been made in a miniature cryogenic diamond anvil cell (DAC). The results reported cover a wide range of materials and many different aspects are discussed. This in part serves to demonstrate the versatility and importance of the technique. New developments in DAC technology are fully described, in particular the introduction of electrical feedthroughs and the importance of the gasket geometry. The technologically important material system GaAs/AlXGa1-X As has been studied under hydrostatic pressure. Band offsets and their pressure dependencies are determined with spectroscopic accuracy and show interesting deviations from the expected behaviour. The effect of substrate orientation on the band offsets has also been investigated. The binding energy of excitons in GaAs/AlAs super lattices in the vicinity of F-X (Type I to Type II) crossover is measured for the first time. The emerging new material systems containing strained layers have been studied, particularly In GaXAs1-X grown pseudomorphically on GaAs. In this system the pressure coefficients of the PL from strained quantum wells are found to have an unexpected dependence on the composition. Comparison with strained InAs/InP quantum wells suggests that this is in fact a strain effect rather than alloy. The band line-up in InXGa1-XAs/GaAs and InXGa1-XAs/AlyGa1-y As quantum well structures is determined from the crossing of P and X states. A preliminary study of the dilute magnetic semiconductor Cd1-XMnXTe is made. High pressure magnetic field measurements on this material are expected to yield information on the nature of the exchange interactions. To this end CdTe/CdMnTe super lattices have been characterised under hydrostatic pressure. Films of a-Si:H are studied under pressure. The intensity of the PL is found to be maintained upto ~90 kbar, in contrast with previous published data. The PL exhibits a small red shift of 1.9 meV/kbar which is compared with the pressure coefficients of the PL from other amorphous materials.
18
Lefez, Benoît. "Caractérisation d'oxydes de cuivre par photoluminescence." Rouen, 1991. http://www.theses.fr/1991ROUES047.
Full textAbstract:
La caractérisation d'oxydes de cuivre par photoluminescence a nécessité le développement d'un spectrofluorimètre. La sensibilité de la méthode a été testée sur des échantillons non-stoichiométriques. La corrélation de données obtenues par différentes méthodes optiques (spectroscopie de réflexion dans l'ultraviolet proche infrarouge, photoluminescence) a permis de préciser les domaines énergétiques mis en jeu lors des transferts radiatifs. La structure et la composition d'un film d'oxydation multicouches ont été établies (spectroscopie dans l'infrarouge, microsonde de Castaing). Un oxyde de cuivre(i), de composition Cu302, a été caractérisé. Différentes applications de la photoluminescence ont été proposées telles que l'aide à l'analyse de la corrosion d'un laiton ou la mise en évidence d'une étape de l'absorption dissociative de l'oxygène
19
Islangulov, Radiy Rashitovich. "Low Power Photoluminescence and Photochemical Upconversion." Bowling Green State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1162244082.
Full text
20
Olsen, Anita. "Thermal Quenching of Photoluminescence from GaN." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2796.
Full textAbstract:
GaN is a III-V semiconductor that is a promising material used in production of light emitting devices and high power/high frequency electronics. The electronic and optical properties of GaN are subdued by defects that occur during the growth processes of this material. The emitted photoluminescence (PL) from optically excited GaN gives insight into the origins and effects of point defects within the crystal lattice structure of GaN. In this study, PL spectroscopy is used to examine and analyze the point defects that occur in Zn-doped GaN. The blue luminescence band seen in undoped and Zn-doped GaN have identical fine structure and properties. This band is attributed to a ZnGa acceptor. In Zn-doped, the PL intensity quenches abruptly at certain temperatures, which increase with increasing excitation intensity. This behavior is different from the PL quenching in undoped GaN. The PL behavior was simulated with a phenomenological model based on rate equations. A program created with mathematical modeling software, in conjunction with the basic rate equations, was used to explain the unusual behavior of the abrupt thermal quenching observed in Zn-doped GaN.
21
Jain, Swati. "Photoluminescence study of cadmium zinc telluride." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1876.
Full textAbstract:
Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains x, 84 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 79-83).
22
Patel, Bhavnesh. "Photoluminescence and kinetics of zinc oxide doped with rare earths." Ohio : Ohio University, 1998. http://www.ohiolink.edu/etd/view.cgi?ohiou1176402695.
Full text
23
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.
Full text
24
Zhao, Shen. "Propriétés optiques de nanorubans et boites quantiques de graphène." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN032/document.
Full textAbstract:
Ce manuscrit présente une étude expérimentale sur les propriétés optiques des nanorubans de graphène (acronyme anglais : GNRs) et des boites quantiques de graphène (acronyme anglais : GQDs) synthétisés par la chimie ascendante.Pour la partie sur les GNRs, les spectres d'absorption et de photoluminescence ainsi que les mesures de la durée de vie sur la dispersion impliquent la formation d'états excimères résultant de l'agrégation des GNRs. Au moyen de la microscopie confocale et de la microscopie à force atomique, nous observons l'émission de petits agrégats de GNRs confirmant leur capacité à émettre de la lumière à l'état solide. D'autre part, les caractérisations optiques des GNRs synthétisés sur une surface d’or présentent des caractéristiques de Raman remarquables, impliquant les propriétés vibrationnelles spécifiques des GNRs par rapport au graphène et aux nanotubes de carbone. La PL observée est spectralement large avec une énergie plus élevée que celle de la bande interdite des GNRs. Cela pourrait être lié aux défauts créés lors de la préparation de l'échantillon.Pour la partie sur les GQDs, les résultats de spectroscopie optique indiquent que les GQDs sont individualisées en dispersion plutôt que sous la forme d’agrégats. Ensuite, grâce à la microphotoluminescence, nous abordons directement les propriétés intrinsèques des GQDs uniques. Des mesures de corrélation de photons de second ordre révèlent que les GQDs présentent une émission de photons uniques avec une grande pureté. De plus, l'émission de GQD présente une bonne photo-stabilité avec une brillance élevée. Comme premier exemple de l'accordabilité optique des GQDs via le contrôle de la structure, nous observons que l'émission de GQDs fonctionalisés avec des atomes de chlore est décalée de près de 100 nm tout en maintenant une émission de photons uniquesThis manuscript presents an experimental study on the optical properties of graphene nanoribbons (GNRs) and graphene quantum dots (GQDs) synthesized by bottom-up chemistry.For the part on GNRs, the optical absorption and photoluminescence spectra as well as the life-time measurements on the dispersion of solution-mediated synthesized GNRs implies the formation of excimer states as a result of aggregation of GNRs. By means of confocal fluorescence microscopy and atomic force microscopy, we observe the emission of small GNR aggregates confirming the ability of GNRs to emit light in the solid state. On the other hand, the optical characterizations of on-surface synthesized GNRs shows remarkable Raman features, implying the distinct vibrational properties of GNRs compared to graphene and carbon nanotubes. The observed PL is spectrally broad with higher energy instead of a bright bandgap emission, which might be related to the defects created during the sample preparation.For the part on GQDs, the optical spectroscopy results indicate that GQDs are individualized in dispersions rather than in the form of aggregates. Then by means of microphotoluminescence, we directly address the intrinsic properties of single GQDs. Second-order photon correlation measurements reveal that GQDs exhibit single-photon emission with a high purity. Notably, the emission of GQDs has good photo-stability with high brightness. As a first example of the optical tunability of GQDs through the control of their structure, we observe that the emission of single edge-chlorinated GQDs is redshifted by almost 100 nm while maintaining the single-photon emission
25
Feng, Lin. "Photoluminescence studies of single zinc oxide nanostructures /." View abstract or full-text, 2010. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202010%20FENG.
Full text
26
Mbulanga, Crispin Munyelele. "Defect-related photoluminescence of zinc oxide nanorods." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/10318.
Full textAbstract:
In this dissertation, Zinc oxide (ZnO) nanorods grown by a two-step chemical bath deposition method on Si substrate is characterized. Research was conducted on ZnO nanorods for the understanding of their optical properties at room temperature (RT), with the emphasis on the visible luminescence. To this end, controlled thermal treatments of as-grown ZnO nanorods were conducted under different conditions, such as annealing time and environment, at atmospheric pressure. Results related to the following studies are reported: an investigation of the structure of ZnO nanorods, an analysis of the chemical composition of the surface, an investigation of the surface stoichiometry of the rods, and a study of defect-related photoluminescence of ZnO nanorods upon thermal treatment in different ambients.To achieve this, the samples were investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and room temperature (RT) photoluminescence Spectroscopy (PL). As-grown ZnO nanorods exhibit a hexagonal shape and have the wurtzite structure; they have, respectively, an average length and diameter of ~900 nm and ~50 nm, and most of the rods are perpendicular to the substrate. The main extrinsic species found in as-grown nanostructures are C, H, F, S, and Cl. ToF-SIMS and XPS confirmed the presence of H related-defects, and the oxygen 1 S XPS peak at 531.5 eV is therefore assigned to oxygen bound to H-related defects. Based on stoichiometry studies, it is found that the near surface regions of as-grown ZnO nanorods (2 to 10 monolayers) are rich in Zn. The RT luminescence of as-grown ZnO nanorods exhibits a near band edge emission centered at ~379.5 nm and deep level emission extending from ~450 nm to ~850 nm. When these nanorods are thermally treated at high temperatures (>850 oC), it is found that even though their crystalline quality is preserved, their morphology is significantly affected, regardless of annealing ambient. Furthermore, in the near surface regions of annealed ZnO nanorods it is found that the Zn/O stoichiometric ratios deviate from unity. Specifically, oxygen vacancies form within the first 100 nm from the sample surface. Further from the surface, the material is deficient in Zn. It is deduced from XPS and AES that the ambient affects the activation rate of intrinsic defects. Furthermore, the only extrinsic defects that are affected by thermal treatment are found to be H-related defects. At high annealing temperatures (300 oC to ~700 oC), H-related defects are removed, and this removal process is found to affect significantly the RT luminescence properties of ZnO nanorods. Specifically, hydrogen passivates vacancy-related defects, depending on the thermal treatment. PL spectroscopy is used to follow this passivation effect as a function of annealing temperature, which causes an initial quenching followed by an enhancement of the green and the red luminescence, regardless of the ambient. Finally, the green luminescence that arises following annealing above ~800 oC is assigned to Zn vacancy-related defects, while the red luminescence that dominates the visible band of ZnO nanorods upon annealing between 400 oC and 600 oC is suggested to be due to oxygen vacancy-related defects.
27
Degliame, Gary. "Thermométrie par photoluminescence, application en micro/nanothermique." Thesis, Reims, 2017. http://www.theses.fr/2017REIMS021/document.
Full textAbstract:
Ce travail de thèse porte sur l’étude de la photoluminescence de microcristaux en vue de concevoir une sonde hybride permettant des mesures de la température et de la conductivité thermique d’un échantillon aux micro/nano-échelles. Pour cela, une sonde thermorésistive en Wollaston, utilisée en microscopie thermique (SThM), a été couplée à un microcristal de Cd0.7Sr0.3F2 (4% Er3+) dopé Erbium dont le spectre d’émission est sensible à la température. Dans un premier temps, les propriétés optiques du cristal massif ont été étudiées en vue de son application en thermométrie. Nous avons travaillé à l’interprétation de son spectre de luminescence obtenu par up-conversion avec une diode laser centrée à 655 nm de 4mW. Nous avons alors proposé trois méthodes de détermination des intensités de fluorescence pour accéder à cette température via la technique RIF (Rapport des Intensités de Fluorescence). Nous avons montré qu’il était possible de déterminer sa température en utilisant les intensités des émissions des sous-niveaux Stark des niveaux thermalisés. Nous avons, ensuite, étudié le comportement en température de microcristaux fixés individuellement à l’extrémité de sondes thermorésistives. Les résultats expérimentaux ont permis d’en déduire la taille optimale du microcristal et la méthode de détermination des intensités la plus adaptée à la nano/microthermométrie.Après avoir validé notre approche de la température aux microcristaux, nous nous sommes intéressés au principe d’imagerie en température à partir des spectres de photoluminescence. Nous présentons une application sur un microsystème composé de fils conducteurs de 350nm de diamètre recouverts par un film mince de SiO2This PhD work focuses on the study of microcrystals photoluminescence in order to design a hybrid probe allowing micro/nano-scales measurements of a sample’s temperature and the thermal conductivity. Thus, a Wollaston thermoresistive probe used in thermal microscopy (SThM), was coupled to an Erbium doped microcrystal of Cd0.7Sr0.3F2 (4% Er3+), whose emission spectrum is sensitive to the temperature.At first, for its applications in thermometry, the optical properties of the bulk crystal have been studied. We worked on the interpretation of its luminescence spectrum obtained by up-conversion using a laser diode centered at 655 nm and 4mW. Then, we proposed three methods to determine the fluorescence intensities to access this temperature via the RIF (Fluorescence Intensity Ratio) technique. We have shown that it is possible to determine its temperature using the Stark sub-levels of the thermalized levels emissions intensities.Furthermore, we studied the temperature behavior of the microcrystals individually fixed at the end of thermoresistive probes. The experimental results made it possible to deduce the optimal size of the microcrystal and the most adapted intensity determination method for nano/microthermometry.After validating our microcrystal temperature approach, we focused on the principle of temperature imaging from photoluminescence spectra. We present an application on a microsystem composed of wires with a diameter of 350nm covered by a SiO2 thin film
28
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.
Full text
29
Dybiec, Maciej. "Spatially resolved photoluminescence spectroscopy of quantum dots." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001767.
Full text
30
McGhee, Ewan James. "The photoluminescence spectroscopy of single quantum dots." Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/1116.
Full text
31
Winser, Andrew James. "Photoluminescence studies of arsenic-doped gallium nitride." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405387.
Full text
32
Toft, Ian. "Fibre optic micro-photoluminescence of quantum nanostructures." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614103.
Full text
33
Starck, Christophe. "Caractérisation de doubles hétérostructures laser par photoluminescence." Toulouse, INSA, 1990. http://www.theses.fr/1990ISAT0008.
Full textAbstract:
Ce memoire presente la mise au point d'une methode de caracterisation de doubles heterostructures laser gainasp/inp realisees par epl et ejm. Cette methode repose sur la determination semi-quantitative du rendement de photoluminescence de la couche active mesure dans des conditions d'injection proches du seuil laser. Nous precisons les conditions experimentales (excitation directe de la couche active, p=10#4 w/cm#2) permettant de generer une densite de porteurs voisine du seuil et montrons que la mesure du rendement dans ces conditions permet de prevoir la densite de courant de seuil des lasers. Le banc experimental permet de realiser d'une part des cartographies rapides de photoluminescence a 300 k et a forte excitation sur des substrats de diametre 50 mm ainsi que des analyses spectrales a 4,2 k. Nous precisons les limitations physiques de la methode provenant de l'echauffement a forte excitation et de phenomenes d'interferences optiques modulant le spectre emis. Nous presentons des applications de cette methode: utilisation de la cartographie pour reveler des defauts de croissance et estimation de la vitesse de recombinaison d'interface gainasp/inp. Nous avons egalement analyse la qualite des hetero-interfaces realisees par ejm en etudiant les spectres de photoluminescence a basse temperature de puits quantiques gainas/inp et gainas/gainasp
34
Shevchenko, D., V. V. Kononets, D. Dobrovolskas, S. Neicheva, N. G. Starzhinskiy, O. Ts Sidletskiy, K. Lebbou, and G. Tamulaitis. "Photoluminescence Inhomogeneity of LGSO : Ce Scintillator Crystal." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35261.
Full textAbstract:
Spatial distribution of photoluminescence (PL) parameters in Lu2SiO5 : Ce (LSO : Ce) and Lu2xGd2 – 2xSiO5 : Ce (LGSO : Ce) are investigated using confocal microscopy. The PL spectra of both crys-tals are dominated by a single band peaked at 510 nm. A low intensity sub-band peaked at 600 nm is observed in LGSO:Ce. Spatial inhomogeneities down to submicron size are observed in spectral center of mass mapping images of LGSO : Ce while the spatial distributions of spectrally-integrated PL intensity and PL peak position showed no large variations. The inhomogeneities in LGSO : Ce are caused by the spectral variation of the long-wavelength sub-band and are attributed to Ce3+ located in CeO6 polyhedra. The results are explained by Lu / Gd ratio fluctuations in mixed LGSO : Ce crystals.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35261
35
Tsagli, Kelvin Xorla. "Temperature Dependence of Photoluminescence Spectra in Polystyrene." University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1625744248503334.
Full text
36
Johnson, Matthew Bruce McGill T. C. McGill T. C. "Ultrafast time-resolved photoluminescence studies of GaAs /." Diss., Pasadena, Calif. : California Institute of Technology, 1989. http://resolver.caltech.edu/CaltechETD:etd-02062007-105824.
Full text
37
Sun, Yuxuan. "Setup for Micro Photo- and Electro-Luminescence of Optoelectronic Device Structures." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175708.
Full textAbstract:
Photoluminescence (PL) is an optical emission induced by photon absorption in a material where electrons are excited from the ground state to excited states, then relax to the lowest excited states and recombine radiatively. The PL emission provides vital information on bandgap energy, material purity and crystal quality. In this project, a PL characterization system, also capable of electroluminescence (EL) measurements, was designed and assem- bled to measure optoelectronic device structures with the capabilities of recording PL or EL spectra as well as micrometer-resolved PL or EL maps on device structures or active components. In order to realize the system with the above functions, an optical setup and a monochro- mator were used to achieve micrometer-range resolution and reasonable signal-to-noise ra- tio. A hardware control platform needed to be designed and assembled to control the precise movement of the sample stage and monochromator as well as for acquiring the signal. A PC-based control software were developed for fully automatic measurements . Furthermore, adequate alignment and calibration methods had to be developed to tune the optical path, monochromator and control program. The setup employs the basic ideas of confocal microscopy, with the parallel laser input focused on the sample surface with a spot diameter of 0.78 μm. A Czerny Turner diffraction grating based monochromator is used to measure PL emissions. A 532 nm laser diode and an InGaAs or Si detector are applied in the system for spectral range of detection of at least 850- 1600 nm, i.e. covering the important data and tele communication bands. The project builds on a platform containing EasyDrivers, an Anduino Uno micro-controller and a Labview based operation software, together working with an amplifier circuit for stepper motors actuation and signal acquisition. Finally, different quantum well samples were measured, showing that the wavelength accuracy and resolution as well as the program flexibility meet the specifications of the setup.
38
Vautravers, Nicolas R. "Polyhedral oligomeric silsesquioxanes in catalysis and photoluminescence applications." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/729.
Full text
39
Skarpeteig, Jon. "Cryogenic micro-photoluminescence of silicon solar cell materials." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11106.
Full textAbstract:
A literature review of relevant luminescence spectra for silicon solar cell materials has been performed. Three multi crystalline silicon samples in particular has been the focus of attention, one electronic grade sample R6, and two solar grade samples ES1, and MH2, where MH2 has added chromium. A list of relevant luminescence spectra has been compiled, and can be found in the appendix.The samples was measured using low temperature micro photoluminescence. They where cooled down by liquid helium in a cryostat, and excited using a laser. Photoluminescence was captured by a camera mounted on a spectrometer. Noise components was measured and removed, but are subject to changes in between measurements, causing some unwanted artifacts to appear in the end result.Luminescence due to P and B doping atoms are identified in ES1, and MH2 as expected, and a weak boron bound exciton line is also present in the clean sample R6. R6 also show signs of having a carbon-carbon complex impurity forming at grain boundaries. Lines attributed to chromium boron pairs where not observed in MH2, presumably due to the lack of such pairs. ES1 exhibits a luminescence attributed to a higher quality material, than both MH2, and R6. Expected behavior is for R6 to have such traits, but this is not the case. The reason for ES1 to show this enhanced luminescence is not known. Lines attributed to dislocations are observed in all the samples, but consist of less intense peaks than expected.Local heating is a severe problem using micro photoluminescence. Bound excitons, impurity lines, and dislocation related lines, all loose intensity at higher temperatures. The intrinsic TO line also have a substantial broadening with respect to energies, suggesting that local temperatures are as much as 70K higher than the sample holder temperature, when exciting with 128 mW using a 2 µm spot diameter.
40
Crandles, David A. "Photoconductivity and photoluminescence in ZnIn(2)S(4)." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4565.
Full text
41
Song, Young Wook. "Photoluminescence of InN with Mg and Zn Dopants." Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/1638.
Full textAbstract:
The optical properties of Mg-doped InN thin films grown on YSZ substrates have been investigated by photoluminescence (PL). A series of InN:Mg samples with various Mg cell temperatures (TMg) were produced by molecular beam epitaxy. The effect of Mg concentration on PL emission properties have been explored by various excitation power and temperature dependent measurements. The PL spectra as a function of excitation power exhibited a pronounce blueshift, indicating prominent band filling caused by the Burstein-Moss effect. Meanwhile, a typical redshift was observed as temperature increased due to bandgap shrinkage. The samples with TMg below 210 ˚C have a dominant peak at energy of 0.68 eV. In contrast, the PL peak emissions for films with a high TMg between 210~230 ˚C were centred near 0.6 eV. No PL emission was observed from the films with TMg above 230 ˚C. By fitting with an empirical Arrhenius equation, the activation energies yield approximately 20 meV and 15 meV for the lower and higher energy transitions, respectively. The fundamental optical properties of Zn doped InN were also examined. InN:Zn films were grown under In-rich conditions. The samples showed well defined PL emission spectra implying that the quality of the film has been improved over the Mg-doped series. The PL spectra of InN:Zn exhibited prominent features containing various emission peaks. The combination of excitation power and temperature dependent measurements supports a precise determination for the origins of the observed transitions. The comparison between the optical properties of Mg and Zn doped InN provide the motivation for more precise quantitative interpretation of p-type InN.
42
Thảo. "Photoluminescence spectroscopy on erbium-doped and porous silicon." Amsterdam : Amsterdam : [s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/83659.
Full text
43
Song, Young-Wook. "Photoluminescence of High Quality Epitaxial p-type InN." Thesis, University of Canterbury. Physics and Astronomy, 2013. http://hdl.handle.net/10092/8101.
Full textAbstract:
Indium nitride (InN) is a group III-V semiconductor that is part of the Al,Ga:N family. It is an infrared bandgap semiconductor with great potential for use in photovoltaic applications. Being an intrinsically n-type material, p-type doping is naturally one of the ongoing hot topics in InN research, which is of interest in the fabrication of pn junctions.
Plasma-assisted molecular beam epitaxy (PAMBE) grown Mg doped InN thin film was investigated via systematic optical characterizations. Photoluminescence (PL) measurement has been a key part of the research, exhibiting a wide range of spectral lines between 0.54 and 0.67 eV. In a critical Mg concentration range of 2.6×10¹⁷ and 1.0×10¹⁸ cm⁻³, a strong luminescence line at 0.6 eV has been associated with a Mg-related deep acceptor. Correspondingly, a variable magnetic field Hall (VFH) effect measurement has successfully
probed a buried hole-mediated conductivity path underneath a surface electron accumulation layer. This specific doping range also led to a manifestation of a “true” band-to-band transition at 0.67 eV. Such an observation has not previously been reported for InN and in our case this assignment is convincingly supported by the quadratic characteristic of the
excitation power law. This established that a rigorous control of Mg flux can sufficiently compensate the background electron concentration of InN via the substitutional incorporation on In sites (Mg_In). However, introduction of donor-like complexes somewhat suppressed this process if too much Mg or even alternative dopants such as Zn and Mn were used. Also distinctively observed was a strongly quenched PL quantum efficiency from heavily doped films, where time-resolved differential transmission (TRDT) measurement showed a biexponential carrier lifetime decay curve owing to the onset of Auger recombination processes. These observations certainly have profound implications for devices and beyond.
44
Richter, Robert [Verfasser]. "Photoluminescence of Diamondoids: Experiment and Theory / Robert Richter." Berlin : epubli GmbH, 2015. http://d-nb.info/1078816085/34.
Full text
45
Ediger, Matthias. "Photoluminescence from charged excitons in single quantum dots." Thesis, Heriot-Watt University, 2006. http://hdl.handle.net/10399/196.
Full text
46
Cheng, Yu-li, and 鄭育俐. "Photoluminescence, Photoluminescence Excitation and Absorption of m-GaN." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/bj6tyu.
Full textAbstract:
碩士國立中山大學
物理學系研究所
95
Group III nitrides have recently attracted great interest and are intensively studied for that cover continuously from the ultraviolet to nearinfrared region by proper alloying.Therefore, group III nitrides have wide applications inoptoelectronic devices, such as light-emitting diodes,ultraviolet or blue lasers, and full color displays. Unintentionally doped m-GaN thin films have been epitaxially grown on LAO by PAMBE. The optical characteristics were investigated with photoluminescence (PL), photoluminescence excitation (PLE), and absorption spectrum.
47
Wang, Wen-Han, and 王文瀚. "Photoluminescence of CulnS2." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/59588748655310179611.
Full text
48
Lai, Jui-Feng, and 賴瑞豐. "Photoluminescence from nc-SiOx:H." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/51235886546820410587.
Full textAbstract:
碩士國立中興大學
精密工程研究所
93
Abstract In this thesis, the amorphous silicon oxide (SiOx) films with various O/Si ratios were deposited by plasma-enhanced chemical vapor deposition with the pulse-modulated RF power. The influence of the pulse-on time (ton) on the O/Si ratio of the SiOx films was elucidated. These amorphous SiOx films were then annealed in N2 atmosphere at 1100℃ for 30 min to be converted into nc-SiOx films. The intensities and the peak positions of the photoluminescence (PL) of these nc-SiOx films were measured to explore how the O/Si ratio of the as-deposited amorphous SiOx films affects the PL signals of the obtained nc-SiOx films after annealing. The chamber pressure, SiH4/N2O/H2, the plasma power, the pulse-off time (toff), and the substrate temperature were fixed at 0.3 torr, 4/12/80 sccm, 30 W, 50 ms, and 70 ℃, respectively. The ton was varied from 2, 5, 12, 25, 50, 100, 150, 200, 325, 450, 800, 1200 ms, to continuous wave (cw). The thickness of all SiOx thin films was fixed at 310 nm, and the Si-O bonding modes of the SiOx films were measured by Fourier transform infrared spectrometer (FTIR). Energy dispersive spectrometer (EDS), Raman scattering spectrometer, x-ray diffraction (XRD), and high resolution transmission electron microscope (HRTEM) were used to measure and analyze the O/Si ratio and the crystalline structures and sizes of the nc-SiOx films. EDS results show that, the O/Si ratio of the SiOx films can be controlled between 0.1 and 0.57 for ton changed from 5 to 800 ms in the condition of N2O/SiH4 = 3. FTIR measurements display that there are three peaks of 850 cm-1 (Si-O bending mode), 1060 cm-1 (Si-O-Si stretching mode), and 2240 cm-1 (H-Si-O stretching mode) in each samples. For the ton = 200 ms sample, which the O/Si ratio is 0.57, the intensities of the 850 cm-1 and 2240 cm-1 peaks are in between those of the other samples, and the intensity of the 1060 cm-1 peak is close to the maximum value of all samples. The background fluorescence intensities of the Raman scattering of the nc-SiOx films obtained after annealing is lager than those of as-deposited amorphous SiOx films about 1 to 2 orders. Especially, the ton = 200 ms sample has the maximum value about 92 times. The results indicate that the increasing of the background fluorescence of Raman scattering is due to light scattering from the nanocrystalline silicon (nc-Si) existed in the nc-SiOx films. XRD results present that there are four distinct crystalline signals at , , , and in the ton = 200 ms sample. The peak positions of the PL signals of all nc-SiOx films are located at about 800 nm. The PL intensity of the nc-SiOx film is increased as the O/Si ratio increases from 0.1 to 0.57. The ton = 200 ms sample exhibiting maximum O/Si ratio (0.57) has the strongest PL intensity. Notely, the small variation of peak positions of all samples implies that there is little change in the size of nc-Si in all samples. The variation of PL intensity is mainly influenced by the fraction of nc-Si in nc-SiOx films. The HRTEM data of ton = 200 ms sample shows that the size of the nc-Si is about 3 nm. The fraction of nc-Si in nc-SiOx film is about 33 %, which is estimated from the area ratio of the nc-Si in nc-SiOx film. The O/Si ratio of the SiOx thin films can be effectively controlled by modulating ton of the pulse-modulated RF power. The PL intensity of the nc-SiOx thin films increases as the O/Si ratio increases from 0.1 to 0.57. The PL intensity of the nc-SiOx films is mainly affected by the fraction of nc-Si in nc-SiOx films.
49
Li, Chung-li, and 李中立. "Photoluminescence of Stereoregular Polymers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/01855021877245218250.
Full textAbstract:
碩士國立中山大學
材料與光電科學學系研究所
100
A series of stereoregular polymers including atactic, syndiotactic and isotactic poly 4(N, N-diphenyl)styrene (PNNDPS) and poly 4(N, N-ethylphenyl)styrene (PNNEPS) were synthesized to exam the tacticity effect on the photoluminescence (PL) behavior. Also, different degrees of the regularity as well as the chemical modification of the fluorophor were explored in the stereoregular polymers. Because of the increase of the steric hindrance among the bulky triphenylamine pendants in the polymer chains, a red shift of the PL emission with an accompanying increase in the emissive intensity was found in contrast to the weakened emission of triphenylamine monomers. In solution state, the PL spectra of these stereoregular polymers reveal multiple PL emissive bands including monomeric and aggregation emissions as evidenced by the time-resolved lifetime measurement. Because of the huge triphenylamine pendants, the triphenylamine pendants attached on the iPNNDPS17 (mmmmmm~50%) might encounter higher steric hindrance than that in the sPNNDPS23 (rrrrrr~59%) due to the stereoregularity evidenced by simulation. Accordingly, the iPNNDPS17 (mmmmmm~50%) exhibits more emissive intensity than the sPNNDPS23 (rrrrrr~59%) due to the effective blockage of the intramolecular rotation of the phenyl blade i.e., the restriction of intramolecular rotation (RIR). Accordingly, the RIR-active PNNDPS is highly sensitive to the temperature variations. The chemical modification of the fluorophor was carried out to examine the effect of the chemical structure. By comparison, the sPNNDPS2 (rrrrrr~70%) with high regularity exhibits much higher emissive intensity than the sPNNDPS23 (rrrrrr~59%) with low regularity due to the less solubility. However, more intense PL emission can be found in the sPNNEPS17 than aPNNEPS8 due to the ethyl substitution of the fluorophor. In aggregation solution, with the increase of the poor water contents, the PL emission decreases significantly in the sPNNDPS23 (rrrrrr~59%) and sPNNDPS2 (rrrrrr~70%) due to the formation of H-aggregate in which extra energetic loss is conducted. By contrast, the PL spectra display that the emissive intensity decreases first as fw=0.1~0.5 and then intensifies later as fw=0.6~0.9. This might be resulted from the competition between the π-π interaction and RIR effect. Interestingly, the PL emissive intensity drops down significantly in the sPNNEPS, whereas the PL emissive intensity is almost unchanged in the aPNNEPS8 with the increase of the poor water contents. We suggest that because the aPNNEPS8 might contain both syndiotactic and isotactic configurations, the isotactic configurations having the ethyl group pointing out of the plane may prevent the formation of the π-stacking between the fluorophors. The PL behavior in thin film is also explored for these stereoregular polymers. After slow cooling from melt, the crystalline sPNNDPS2 (rrrrrr~70%) thin film exhibits very strong emission in comparison with the thin film after quenching from melt, indicating the crystallization-induced emission enhancement. Although the iPNNDPS17 (mmmmmm~50%) is noncrystallizable as evidenced by differential scanning calorimetry (DSC) and polarized light microscope (PLM), the PL emissive intensity of the iPNNDPS17 (mmmmmm~50%) thin film is significantly stronger after slow cooling from melt than that after quenching from melt. We suggest that this might be attributed to the free volume effect varied with the thermal history associated with the steric hindrance. Notably, this enhanced PL emission in the iPNNDPS17 (mmmmmm~50%) thin film is extremely larger than that in the sPNNDPS23 (rrrrrr~59%) and aPNNDPS8, indicating the stereoregularity effect associated with the RIR effect. By contrast, this free volume effect is not significant in the PNNEPS thin film due to the flexible ethyl substitutions. As a result, the stereoregular polymers with different tacticities and regularities indeed exhibit distinct PL behavior in solution and thin film.
50
Yang, Tun-Chun, and 楊敦鈞. "Studies of Surface V-Defect on AlGaN Films by Micro-Photoluminescence and Photoluminescence Excitation." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/97941997470701756550.
Full textAbstract:
碩士國立交通大學
電子物理系
91
We have studied optical properties of AlGaN films grown by metal organic chemical vapor phase epitaxy under various ammonia flow rate. From micro-photoluminescence (Micro-PL) spectra, there is an extra peak in the V-defect, which is 0.1 eV lower than the near band edge emission. The origin of this extra peak is the defect band induced by V-defect. In order to determine the characteristics of Inbe, and IV, the excitation power dependent measurements were carried out indicating that they are not from donor-acceptor pair (DAP) transitions. Furthermore, the temperature dependence of Micro-PL was studied and the S-shape behavior was observed in the spectrum as due to the spatial fluctuation, for instance, Ga vacancy formed localized states. For Al0.9Ga0.91N, the activation energy of 27.8 meV and the exciton localization energy of 6.1 meV film for Inbe were obtained from the Arrhenius plot. However, for IV, the activation energy increases to 65.1 meV and the localization energy increases to 7.6 meV. By using the photoluminescence excitation (PLE) technique, we found that the V-defect created new energy levels that are responsible for the new IV emissions. We suggested that the broad band from the V-defect is probably related to acceptor-like level due to Ga vacancy.