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This thesis investigates the use of an avalanche Platinum Silicide (PtSi) Schottky Barrier Diode as a detector in fiber optic communication systems for the 1.3 to 1.5 mum spectral region. The avalanche process is used to amplify the signal prior to electrical interfacing in order to enhance the signal-to-noise ratio. The amount of multiplication is predicted by the impact ionization coefficients for electrons and holes, alpha and beta, respectively. By using PtSi Schottky diodes, where alpha > beta, pure electron injection can be accomplished by irradiating with photons of energy psi hnu Eg (where psi is the Schottky Barrier height and Eg is the bandgap of silicon), thus maximizing multiplication and minimizing noise. An alternative means for avalanching involves the quantum effects of impurity-band ionization. By using a heavily doped semiconductor and operating at low temperatures, one can achieve noise-free gain at lower electric field strengths. (Abstract shortened with permission of author.)

An experimental and theoretical analysis of the effects of ion bombardment on Schottky diodes is presented. The experimentally observed shifts in diode performance are compared to the conditions of ion exposure. These experiments show that Schottky diodes exposed to ion beams show decreases in effective barrier heights and ideality factors, as well as increased incidence of premature reverse breakdown. The change in barrier height is found to be proportional to the energy of the individual ions and the total number of ions delivered to the surface. A numerical simulation of the damage process and device performance is developed. The model considers only the effect of ion exposure on the potential distribution within the metal-semiconductor junction. Comparison of experimental and modelled barrier shifts shows fair agreement, suggesting that enhancement of tunnelling currents is the dominant mechanism for barrier lowering.

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In the past decades, polymeric light-emitting diode (PLED) have been a focus of research interest to scientists all over the world due to its potential application in flat panel displays. In previous studies, tremendous progresses in material developments, device engineering and theoretical modeling for PLEDs have been achieved. However, there are still a number of crucial problems to be solved in order for PLEDs to be widely employed in commercial flat panel displays. In this thesis, we present studies of PLEDs that used a high work-function metal aluminum as the cathode. The device exhibits a highly enhanced efficiency by modifying the cathode using certain non-ionic surfactant polymers. Based on this finding, we further demonstrated top-emitting PLEDs with environmentally stable cathodes. In another development, we show that a three-coloremitting device with a bilayer emitting polymer structure can be achieved by a dry photo-patterning process. Each of the red, green and blue emission in the device has a comparable emitting efficiency to the traditional standard red, green or blue device with single color emission. These results are believed to be important and beneficial for obtaining low-cost, large-scale and long life-time flat panel displays based on PLEDs. / by Deng Xianyu. / "September 2006." / Adviser: King Young Wong. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1871. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 92-101). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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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.

The widespread adoption of wavelength division multiplexing to increase the bandwidth of optical fiber communication systems has provided a major impetus for research on low cost, single-mode, wavelength stable tunable diode lasers for use in optical telecommunications due to the large volume of lasers required. Other applications, such as demodulation of fiber Bragg grating sensor systems can also make use of inexpensive tunable laser diodes. In addition, the steady increase in the amount of computational power available has led to the widespread use of computers to model physical systems both to predict system performance and to gain insight into physical behavior. Following a brief review of the application and construction of optical fiber Bragg gratings and a discussion of diode lasers and common methods of tuning diode laser wavelengths, a coupled-cavity approach to modeling laser diode output spectra, the construction of a fiber Bragg grating wavelength tunable laser, and the coupled cavity model of the fiber Bragg grating wavelength tunable diode laser are detailed. The physical laser system consists of a commercial Fabry-Perot diode laser with a cavity length of 300 microns, antireflection coated with a single layer of SiO, and coupled into an optical fiber containing a fiber Bragg grating. Wavelength tuning is accomplished by applying axial strain to the fiber grating. The coupled cavity model directly includes the antireflection coating, includes the fiber Bragg grating as an index step, and is the first reported implementation of this method to model fiber Bragg grating coupled laser diodes. The measured output spectra of the physical laser diode system and the calculated output spectra are given and compared. Continuous tuning of the diode laser by applying axial strain to the fiber grating is not observed nor calculated to occur for a single-layer silicon monoxide antireflection coating. To achieve continuous wavelength tuning, better antireflection coatings will need to be developed. / Graduation date: 2004