An optical, contact-free method for measuring minority carrier diffusion lengths is developed and demonstrated for a range of semiconductor materials used in high efficiency triple junction solar cells. This method uses a Scanning Electron Microscope (SEM) coupled with an optical microscope. The diffusion lengths, combined with minority carrier lifetime measured via time-resolved photoluminescence, allow for the computation of minority charge carrier mobility. The technique uses images to extract diffusion length measurements from GaAs, InGaAs, and InGaP heterostructures at different SEM beam energies and probe currents. Excellent correlation between measurements shows the reproducibility of this technique. Diffusion lengths from 2-63 microns have been measured in a variety of GaAs, InGaAs, and InGaP samples. Effects of alloy ordering, doping, and lattice matching have been investigated. Several areas for further research are offered, including detailed radiationdamage mapping of solar cell layers. Further anisotropic studies of the solar cell layers are suggested to investigate the directional dependence of diffusion length within the InGaP heterostructures. Finally, new and emerging solar cell materials would benefit from this technique, allowing for the complete characterization of minority charge transport properties before growing an entire solar cell.

by Cheung Wing-yiu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [170-185]). / ACKNOWLEDGMENT --- p.I / abstract --- p.II / contents --- p.IV / figure captions --- p.C-1 / table captions --- p.C-10 / photo captions --- p.C-11 / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Novel Silicon-Based Materials Structures - Background and Perspectives --- p.2 / Chapter 1.2 --- Light Emission from Porous Silicon --- p.3 / Chapter 1.2.1 --- Quantum size effect --- p.7 / Chapter 1.2.2 --- Chemical luminescence model --- p.9 / Chapter 1.3 --- Germanium Silicon Alloy --- p.11 / Chapter 1.3.1 --- Formation of germanium silicon alloy by ion implantation --- p.16 / Chapter 1.4 --- Scope of this Work --- p.19 / Chapter CHAPTER 2 --- EXPERIMENTAL METHODS --- p.20 / Chapter 2.1 --- Preparation of Porous Silicon Layers --- p.20 / Chapter 2.1.1 --- Anodization --- p.21 / Chapter 2.1.2 --- Post - anodization treatments --- p.25 / Chapter 2.2 --- Preparation of Germanium Silicon Alloy --- p.27 / Chapter 2.2.1 --- Ion implantation --- p.27 / Chapter 2.2.2 --- Thermal treatment --- p.27 / Chapter 2.3 --- Characterization Methods --- p.28 / Chapter 2.3.1 --- Microscopy studies --- p.28 / Chapter 2.3.2 --- Structural studies --- p.30 / Chapter 2.3.3 --- Compositional studies --- p.31 / Chapter 2.3.4 --- Electron spin resonance --- p.32 / Chapter 2.3.5 --- Optical methods --- p.36 / Chapter 2.3.6 --- Electrical measurements --- p.38 / Chapter 2.3.6.1 --- Spreading resistance profiling --- p.38 / Chapter 2.3.6.2 --- Other electrical measurements --- p.40 / Chapter CHAPTER 3 --- POROUS SILICON - RESULTS --- p.41 / Chapter 3.1 --- General observation of on the Appearance of Samples --- p.41 / Chapter 3.2 --- Formation Current Voltage Characteristics --- p.41 / Chapter 3.3 --- Surface Morphology --- p.52 / Chapter 3.4 --- Electron Spin Resonance --- p.56 / Chapter 3.5 --- Composition Characteristics --- p.68 / Chapter 3.6 --- Optical Characteristics --- p.72 / Chapter 3.6.1 --- Infra-red transmittance studies --- p.72 / Chapter 3.6.2 --- Photoluminescence --- p.74 / Chapter 3.7 --- Electrical Properties --- p.82 / Chapter CHAPTER 4 --- POROUS SILICON - DISCUSSION --- p.84 / Chapter 4.1 --- Formation Properties --- p.84 / Chapter 4.2 --- Structural Properties --- p.87 / Chapter 4.3 --- Paramagnetic Centres in Porous Silicon --- p.88 / Chapter 4.4 --- Compositional Properties --- p.93 / Chapter 4.5 --- Photoluminescence --- p.95 / Chapter 4.6 --- Electrical Properties --- p.105 / Chapter 4.7 --- Summary --- p.106 / Chapter CHAPTER 5 --- GERMANIUM SILICON ALLOY - RESULTS --- p.108 / Chapter 5.1 --- Structural Characteristics --- p.108 / Chapter 5.1.1 --- Defect structure --- p.109 / Chapter 5.1.2 --- Crystal structure --- p.115 / Chapter 5.2 --- Optical Characteristics --- p.127 / Chapter 5.3 --- Electrical characteristics --- p.129 / Chapter 5.3.1 --- Spreading resistance profiling --- p.129 / Chapter 5.3.2 --- Other electrical measurements --- p.138 / Chapter CHAPTER 6 --- GERMANIUM SILICON ALLOY - DISCUSSION --- p.142 / Chapter 6.1 --- Structure Analysis --- p.142 / Chapter 6.2 --- Optical Properties --- p.146 / Chapter 6.3 --- Electrical Properties --- p.147 / Chapter 6.4 --- Summary --- p.150 / Chapter CHAPTER 7 --- CONCLUSIONS --- p.152 / Chapter 7.1 --- Porous Silicon --- p.152 / Chapter 7.2 --- Germanium Silicon Alloys --- p.154 / Chapter CHAPTER 8 --- FURTHER WORK --- p.156 / Chapter 8.1 --- Porous Silicon --- p.156 / Chapter 8.2 --- Germanium Silicon Alloys --- p.156 / APPENDIX / Chapter I --- SPECTRA OF GERMANIUM SILICON ALLOY --- p.A1 / Chapter 1.1 --- Rutherford Backscattering Spectra --- p.A2 / Chapter 1.2 --- Spreading Resistance Depth Profile --- p.A8 / Chapter II --- PUBLICATIONS --- p.A14 / BIBLIOGRAPHY --- p.A15

Ng Ching Man = 在不同氣體中一的維硒化鋅鈉米結構的發光研究 / 吳靜雯. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 67-69). / Text in English; abstracts in English and Chinese. / Ng Ching Man = Zai bu tong qi ti zhong yi de wei xi hua xin na mi jie gou de fa guang yan jiu / Wu Jingwen. / Contents / Acknowledgements --- p.ii / Abstract --- p.iii / Chapter Chapter 1- --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Motivation --- p.3 / Chapter 1.3 --- Our Work --- p.4 / Chapter Chapter 2 - --- Experiment --- p.5 / Chapter 2.1 --- MOCVD System --- p.5 / Chapter 2.2 --- Metalorganic Sources --- p.5 / Chapter 2.3 --- Substrates --- p.7 / Chapter 2.4 --- Growth of ZnSe Nanowires --- p.7 / Chapter 2.5 --- Sample Passivation --- p.8 / Chapter 2.6 --- PL measurements --- p.8 / Chapter 2.7 --- Ambient Gases --- p.9 / Chapter 2.8 --- Gases Handling Apparatus --- p.9 / Chapter 2.9 --- Ambient Gases and Laser Power Control in PL Measurements --- p.11 / Chapter Chapter 3 - --- Characterization --- p.13 / Chapter 3.1 --- Photoluminescence --- p.13 / Chapter 3.2 --- Secondary Electron Microscopy --- p.14 / Chapter 3.3 --- X-Ray diffraction --- p.15 / Chapter Chapter 4 - --- Results --- p.16 / Chapter 4.1 --- ZnSe Nanowires Grown on Si(100) --- p.16 / Chapter 4.1.1 --- Morphology and Structure of the As Synthesized Sample --- p.16 / Chapter 4.1.2 --- Morphology and Structure of the Sample after Passivation --- p.17 / Chapter 4.2 --- Effect of Ambient Condition on Photoluminescence --- p.19 / Chapter 4.2.1 --- PL in Vacuum Ambient --- p.20 / Chapter 4.2.2 --- PL Spectra in different Ambient Gases --- p.21 / Chapter 4.2.3 --- PL Reversibility --- p.23 / Chapter 4.3 --- "Effect of Pressure, Concentration and Power of Excitation on the Photoluminescence of Nanowires" --- p.26 / Chapter 4.3.1 --- Ambient Pressure --- p.27 / Chapter 4.3.1.1 --- H2S --- p.27 / Chapter 4.3.1.2 --- H2 --- p.30 / Chapter 4.3.1.3 --- CO --- p.32 / Chapter 4.3.2 --- Ambient Concentration --- p.33 / Chapter 4.3.2.1 --- H2S --- p.33 / Chapter 4.3.2.2 --- H2 --- p.36 / Chapter 4.3.3 --- Excitation Power --- p.38 / Chapter 4.3.3.1 --- H2S --- p.38 / Chapter 4.3.3.2 --- H2 --- p.40 / Chapter 4.3.3.3 --- CO --- p.41 / Chapter Chapter 5 - --- Discussions --- p.42 / Chapter 5.1 --- Quality of nanowires --- p.42 / Chapter 5.2 --- Surface Reaction --- p.43 / Chapter 5.2.1 --- Surface States --- p.43 / Chapter 5.2.2 --- Gas-surface interaction --- p.46 / Chapter 5.2.2.1 --- Physiosorption --- p.46 / Chapter 5.2.2.2 --- Chemisorption --- p.47 / Chapter 5.3 --- (NH4)2S passivation --- p.48 / Chapter 5.3.1 --- Etching --- p.48 / Chapter 5.3.2 --- (NH4)2S passivation --- p.48 / Chapter 5.4 --- PL increase in Vacuum --- p.50 / Chapter 5.5 --- Effects of different Gases --- p.50 / Chapter 5.5.1 --- H2S --- p.50 / Chapter 5.5.2 --- H2 --- p.53 / Chapter 5.5.3 --- CO --- p.54 / Chapter 5.5.4 --- Other explanations --- p.54 / Chapter 5.6 --- The amount of Intensity Change --- p.56 / Chapter 5.7 --- Rates of Adsorption and Desorption --- p.56 / Chapter Chapter 6 - --- Conclusions --- p.58 / Appendices --- p.60 / Chapter I - --- Fitted parameter of the adsorption and desorption of H2S and CO --- p.60 / Chapter II - --- Calculation of gas and photon fluxes --- p.65 / References --- p.67

No description available.

Organic light emitting diodes (OLEDs) are an emerging display technology with the advantages of being efficient, bright, portable and flexible. In this work, a number of novel compounds have been developed for incorporation into OLEDs as emitting dopants. A series of ligands containing dipyrido[3,2-a:2�,3�-c]phenazine substituted at the 11-position with ethyl ester, bromo-, nitrile and 5-phenyl-1,3,4-oxadiazole moieties have been synthesised. Each of the ligands were coordinated to Re(I), Cu(I), Ru(II) and Ir(III) metal centres. Ligands and complexes were characterised by �H NMR and IR spectroscopy, mass spectrometry and microanalysis. Single crystal X-ray analyses were performed on fac-chlorotricarbonyl(dipyrido[3,2-a:2�,3�-c]phenazine-11-carboxylic ethyl ester)rhenium (triclinic, P-1, a = 6.403(5) Å, b = 10.388(5) Å, c = 16.976(5) Å, α = 84.087(5)�, β = 84.161(5)�, γ = 79.369(5)�, Z = 2, R1 = 0.0536, wR2 = 0.0978), fac-chlorotricarbonyl(11-bromodipyrido[3,2-a:2�,3�-c]phenazine)rhenium.CH₃OH (monoclinic, C2/c, a = 19.506(5) Å, b = 18.043(5) Å, c = 13.320(5) Å, α = γ = 90�, β = 114.936(5)�, Z = 4, R1 = 0.0345, wR2 = 0.0827), fac-chlorotricarbonyl(11-cyanodipyrido[3,2-a:2�,3�-c]phenazine)rhenium (triclinic, P-1, a = 6.509(5) Å, b = 12.403(5) Å, c = 13.907(5) Å, α = 96.88(5)�, β = 92.41(5)�, γ = 92.13(5)�, Z = 2, R1 = 0.0329, wR2 = 0.0701), bis-2,2�-bipyridyl(2-(11-dipyrido[3,2-a:2�,3�-c]phenazine)-5-phenyl-1,3,4-oxadiazole)ruthenium triflate.2CH₃CN (triclinic, P-1, a = 10.601(5) Å, b = 12.420(5) Å, c = 20.066(5) Å, α = 92.846(5)�, β = 96.493(5)�, γ = 103.720(5)�, Z = 2, R1 = 0.0650, wR2 = 0.1458) and bis-(2-phenylpyridine-C�,N�)(dipyrido[3,2-a:2�,3�-c]phenazine)iridium(III) hexafluorophosphate.(CH₃)₂CO (triclinic, P-1, a = 13.505(5) Å, b = 16.193(5) Å, c = 19.788(5) Å, α = 92.857(5)�, β = 98.710(5)�, γ = 93.432(5)�, Z = 2, R1 = 0.0494, wR2 = 0.1097). The ground and excited state properties of the ligands and complexes were investigated by a range of techniques, including electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and excited state lifetime studies. Complexes of dppz-based ligands typically show MOs which are segregated over either the bpy or phz region of the dppz backbone. The properties of the Ru(II) and Ir(III) complexes of the ligand series investigated in this work were consistent with this model, and the LUMOs of these complexes were assigned as the b₁(phz) phz-localised MO. The Re(I) and Cu(I) complexes of the ligand series appeared to show MOs which were delocalised over the entire dppz ligand. A modular complex containing an electron transport group, hole transport group and emitting centre was synthesised. The complex fac-tricarbonyl(trans-(E)-1-((2,2�:5�,2��-terthiophen)-3�-yl)-2-(4�-pyridyl)-ethane)(2-(11-dipyrido[3,2-a:2�,3�-c]phenazine)-5-phenyl-1,3,4-oxadiazole)rhenium(I) hexafluorophosphate was oxidised and reduced readily, encouraging efficient transport of both holes and electrons. However, this resulted in the complex having a small band gap and hence a low quantum yield of emission. Emission from this complex appeared to be from more than one state. The complexes containing the dppz-based ligand series show complicated excited state behaviour. Emission behaviour is consistent with input from more than one state for many of the Re(I), Cu(I) and Ir(III) complexes. The Ru(II) complexes of the ligand series emit from a �MLCT state between metal-based and bpy-based MOs located on the dppz ligands, as is usual for complexes of this type. All complexes containing 11-cyanodipyrido[3,2-a:2�,3�-c]phenazine showed extremely short excited state lifetimes consistent with extremely efficient non-radiative deactivation of the excited state. Ligands and complexes were incorporated into OLEDs with the structure [ITO/PEDOT:PSS/PVK:BuPBD:dopant/BCP/Alq₃/LiF/Al] to test their ability to behave as emissive dyes. Many of the compounds behaved poorly as dopants due to their low emission quantum yields, and poor alignment of HOMO and LUMO energy levels with those of the other compounds within the device. �MLCT-based emission was achieved through energy transfer from the PVK host for the devices containing chlorotricarbonylrhenium(I) complexes of the ligand series. The OLEDs containing Ru(II) and Ir(III) complexes also emitted from dopant-centred �MLCT states. In these devices, dopant excitation appeared to occur through direct charge trapping from the adjacent hole transport and electron transport layers.

As the progress of the precision of optical analysis material, Raman spectra is developed as a popular optical and material analysis method. The samples of Raman spectra are low population and prepared easily and fast. Raman spectra would not destroy the samples. GaN is an ideal blue light substrate and a popular nitrogen compound of semi-conductor in III-V group . The character of the GaN is it has a wild direct band gas, high thermal conductivity and high chemical stability. This study is focus on analyzing if there is any difference of the structure of GaN growing on the different substrates. It is compared with photoluminescence spectrum to make sure the accuracy of the result of Raman spectra.

ZnO thin film is a suitable material for the phosphor layer of green emission of the electroluminescence (EL) device. Therefore, the luminescence mechanism of green emission of ZnO thin film is a key issue to be investigated. In this thesis, ZnO thin films are deposited on SiO2/Si substrates using sol-gel method and sputtering technology, and then post-annealed by a rapid thermal annealing (RTA) process under various annealing temperatures (200¢J~900¢J) and atmospheres (vacuum, ambient atmosphere and oxygen). The physical and photoluminescence (PL) characteristics were first discussed. Secondly, the relationship between the chemical composition and the PL properties were also investigated to figure out the dominant luminescent center of ZnO thin film. Finally, ZnO thin film was applied as the phosphor layer of AC thin film EL device and the characteristics were discussed. According to the experimental results of ZnO thin film prepared using sol-gel method and RTA process, the XRD patterns show a preferred (002) orientation after annealing. The grain size became larger with the increasing annealing temperature. From PL measurement, two ultraviolet (UV) luminescence bands were obtained, and the intensity became stronger when the annealing temperature was increased. The strongest UV light emission appeared at annealing temperature of 900¢J in oxygen. The X-ray photoelectron spectrum (XPS) demonstrated that a more stoichiometric ZnO thin film was obtained upon annealing in oxygen and more excitons were generated from the radiative recombination carriers consistently, and resulted in the strong UV emission. However, no green emission was obtained from ZnO thin film prepared by sol-gel method. The XRD patterns also exit an excellent preferred (002) orientation of ZnO thin film deposited using sputtering and RTA process. The grain size of ZnO thin film annealed at 200¢J~500¢J increased with the increasing annealing temperature, and then exhibited a melting state with the temperature of 600¢J~700¢J. A large and complete grain was observed at the temperature of 900¢J. The PL spectrum illustrated that a stronger UV emission intensity appeared at annealing temperature of 500¢J. On the other hand, the green light emission could be obtained as ZnO films were annealed above 500¢J and reached a maximum intensity at 900¢J. Based on the XPS analysis, the O1s peak of ZnO film revealed that the concentration of oxygen vacancy increased with the annealing temperature from 600¢J to 900¢J under an ambient atmosphere. The PL results demonstrated that the intensity of green light emission at 523nm also increased with temperature. Under various annealing atmospheres, the analyses of PL indicated that only one emission peak (523nm) was obtained, indicating that only one class of defect was responsible for the green luminescence. The green light emission was strongest and the concentration of oxygen vacancies was highest when the ZnO film was annealed in ambient atmosphere at 900¢J. According to the experimental results manifested above, room temperature was used to deposit films to increase the ratio of Zn atoms inside the thin film when using sputtering technique to deposit ZnO thin film. With the modulation of the annealing parameters, stronger green light emission could be obtained. The luminescence mechanism of the emission of green light from a ZnO thin film is associated primarily with oxygen vacancies. In addition, only UV light emission of ZnO thin film prepared using sol-gel method was obtained because of the better stoichiometry.

Thèse de doctorat : Dispositifs de l'Electronique Intégrée : Villeurbanne, INSA : 2002. / Titre provenant de l'écran-titre. Bibliogr. p.139-141.

Thèse doctorat : Dispositifs de l'Electronique Intégrée : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Réf. bibliogr. à la fin de chaque chapitre.

Reproduction de : Thèse doctorat : Physique : Reims : 2007. / Thèse en co-tutelle. Titre provenant de l'écran titre. Bibliogr. f.