The effect of silicon doping on the strain in c-plane InN films grown on c-plane GaN by plasma-assisted molecular beam epitaxy is investigated. Strain is measured by x-ray reciprocal space mapping and Raman spectroscopy. The silicon doping concentration of our sample is about 1018 cm-3 by Hall measurement. Relation between the strain and the silicon concentration is obtained. To understand the increase in tensile stress caused by Si doping is discussed in terms of a crystallite coalescence model.

Recently, synthesis of Diamond-Like Carbon (DLC) films has received considerable interest. Owing to their similar characteristics of diamonds, such as extreme hardness, chemical stability, and high heat conductivity etc, DLC films are regarded as one of the most promising materials. But the practical applications have been limited due to their high internal stress and insufficient adhesion at the interface between DLC film and substrate. Several methods used to the deposition of Me-DLC films have been proposed. Studies have shown that the internal stress was released and the adhesion also improved by doping metallic element into DLC films. Conventionally, metal incorporation in DLC films were prepared by vapor deposition. The requirement of high vacuum equipment makes the process complicated. Besides, there are many merits in electrodeposition, such as low cost, simplicity of experimental set up, and availability for deposition on complex shapes substrate in large area. In this study, electrodepositing technique was used to synthesize the amorphous Cu-DLC films deposited on ITO substrate, in which the pH value of electrolyte varied, to study the characteristics and the composition of DLC films. According to the I-t curves of deposition, the end of current density was used for the impedance comparison of films. With the addition of Cu, the resistance of the electron transportation in Cu-DLC was reduced, and the awl-shaped surface morphology was observed by AFM measurement, which could enhance the electron field emission properties of thin films. For Raman analysis, the effect of Cu addition would promote the sp2 bonding¡F this result corresponds with the increasing ID/IG value. It indicates that film becomes graphitization due to the addition of Cu and leads the shift of G-peak position toward lower wavenumber. ESCA spectra of C1s and Cu2p indicate no obvious evidence of Cu-C formation. The sp2/(sp2+sp3) ratio increases with the pH value. In addition, we found that Cu-DLC in acidic environmental condition, or doping as [Cu(NH3)n]2+ complex is more conducive to the growth of copper metal in DLC films, and has the lowest optical band gap value deduced by n&k analyzer. Finally, we discussed the thin film growth mechanisms and the characteristic of electron field emission for the applications in the future.

The most widely used transparent conducting thin films, Indium-Tin-Oxide (ITO), will surly encounter difficulties for Indium is naturally limited and its price rising fast very year. Searching for Indium free transparent conducting oxides (TCO) becomes one of the important issues in this field. Among of which, ZnO:Al (AZO) is the most import candidate and is used, now, in photovoltaic industry. In the future, flexible substrates are necessary, therefore, to preventing degrading of TCO crystal by repeatedly bending, TCO should be produced in amorphous or nano-crystal types. By properly doping of Ti in ZnO lattice, a certain form of amorphous-nanocrystal mixture films can be obtained at room temperature. Unfortunately, amorphous or nano-crystal with poor crystal structure suppress the electric conduction. Growth films at few hundred degrees may enhance the crystallization, however, the flexible substrate, such as PET, can only sustained temperature lower than 150oC. In this project, an UV assisted film growth technique is used to study the effect of the UV assistant growth on films properties. The aim of this study is wish to grow films with better crystallization at lower growth temperature. Physical properties of films are investigated by the transmittance spectroscopy (N&K analyzer), X-ray dffractometer (XRD) and atomic force microscopy (AFM). It is found that the optical band gap increases and shows an obvious blue shifting due to the short range order in the present films. All films exhibits high level of transparency in the visible range. The grazing angle incident X-ray diffraction (GID XRD) indicates that high ratio of amorphous phase for films grown at high working gas pressure and low RF power. For certain growth conditions, pure amorphous films can be obtained. Oppositely, films grown at low working gas pressure and high RF power manifest crystal growth along all directions resulting shifting and broadening in XRD peaks. Higher the Ti doping levels higher the amorphous ratio. By gown films at higher temperatures, (002) peak dominates the GID XRD measurements. It is found that the 266nm UV assisted growth enhances crystallization and roughness of films at relatively low temperature, lower than the highest sustainable temperature of PET.

Boron-doped carbon nanotubes are predicted to behave as semiconductors over a large range of diameters and chiralities and might thus constitute a suitable class of material for nanoelectronics technology. Boron-doped CNTs were reported as by-products when BC2N nanotubes were prepared by an arc-discharge method. The potential doping of CNTs with different kinds of atoms might provide a mechanism for controlling their electronic properties. We have synthesized boron-doped carbon nanotubes (CNTs) directly on copper catalyst by decomposition of B(OCH3)3 in chemical vapor deposition method. The results were characterized and analyzed by scanning electron microscopy (SEM), Raman, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), solid-state NMR and TGA.

Nitrogen-doped TiO2 nanotubes with enhanced visible light photocatalytic activity have been synthesized using commercial titania P25 as raw material by a facile P25/urea co-hydrothermal method. Morphological and microstructual characteristics were conducted by transmission electron microscopy, powder X-ray diffraction, and nitrogen adsorption/desorption isotherms; chemical identifications were performed using X-ray photoelectron spectroscopy, and the interstitial nitrogen linkage to the TiO2 nanotubes is identified. The photocatalytic activity of all nitrogen-doped TiO2 nanotubes synthesized by different urea content, evaluated by the decomposition of rhodamine B dye solution under visible light using UV¡VVis absorption spectroscopy, is found to exhibit higher degradation rate than that of P25. Factors affecting the photocatalytic activity of RB were analyzed and a possible mechanism of photodegradation was also proposed. The high photocatalytic activity was attributed to the process of two different mechanisms, one was the direct degradation of the chromophoric system and the other was successive deethylation of the four ethyl groups.

The topic of this thesis is solar pump Nd-doped double-clad fiber laser, the main characteristic of this research is we use nature and low pollution source pump unique laser gain medium. By using Neodymium-doped double-clad fiber in form of waveguide structure to replace Neodymium-doped glass, Neodymium-doped yttrium aluminum garnet crystals that have large cross-section area of the volume in the past¡F natural sunlight is used as pumped source in instead of diode laser, pulsed Xenon lamp, Krypton arc lamp¡Ketc. In order to reduce the use of electric power source and decrease the pollution . By using Solar concentration system, we focus average sunlight power density (800W/m2) to very high power density. In application, If lasers are needed in remote locations where sunlight is abundant and other forms of energy sources are scarce, this kind of solar energy usage is not a bad idea.

This thesis presents the fabrication of transparent conductive Boron-Doped CVD diamond (BDD) thin film with the appropriate processing parameters. The BDD shows the transmittance in the visible wavelength and good electrical conductivity. The depositing rate of Diamond films yields 0.37 £gm per hour with Hydrogen, Argon, Methane and oxygen as gas sources, and B(OCH3)3 was used as the doping source. Microwave plasma chemical vapor deposition (MWCVD) was performed for the BDD deposition. Also, PECVD was applied to grow diamond-like Carbon (DLC) film on silicon as substrate. Through systematical experiments, the influence of carrier gas flow rates of B(OCH3)3, the variation of ratio of Argon, and growth pressure of BDD on the transmittance in the visible light and electrical conductivity has been studied. In addition, dc bias was applied to synthesize diamond films and extend long depositing time shows the stable growth rate of diamond films. The thickness of BDD films increases and acquired more than 60% optical transmittance. BDD samples were analyzed by Raman Spectroscopy for the diamond quality, N & K Analyzer for the film thickness and optical properties. Van Der Pauw I-V Measurement and Hall Measurement were analyzed p-type diamond films carrier mobility, carrier concentration, electrical resistivity. By increasing Argon and applying negative dc bias can improve the growth rate and transmittance of diamond films. And the quality of diamond films could be improved by the coating of DLC on Si substrates. This work has achieved fabricating a transparent conducting BDD successfully.

A tunable erbium-doped fiber ring laser using an intra-cavity Fabry-Perot filter as the tuning element is investigated. Tuning is achieved by varying the applied voltage which controls the FP cavity length. The laser's wavelength is monitored using an optical spectrum analyzer to determine the laser's spectral characteristics under static conditions at different wavelengths over its tuning range of approximately 50nm. When the laser is tuned rapidly, the frequency versus time characteristic is determined using a fiber Fabry-Perot interferometer with a photodetector to convert the optical signal to an electrical signal. The core of the research is to determine the degree of spectral broadening of the laser as a function of the spectral tuning rate. The fringe contrast of fiber Fabry-Perot interferometer transmittance curves decreases with increase in the tuning frequency. The gain at a certain wavelength becomes a function of time putting an upper limit on the tuning frequency of the system. The carrier lifetime of erbium ions dictates the maximum achievable tuning speed.

In this thesis, we study a series of Si-doped GaN thin films and nanodots. These samples are growth on c-face sapphire substrate by Molecular Beam Epitaxy. In Si-doped GaN thin film growth, different Si cell temperature are used to control the dopant concentration. Van der Pauw hall measurement is used to measure the carrier concentrations and the mobilities. As increase Si cell temperature, the carrier concentration and the mobility increase. The maximum carrier concentration is 8 ¡Ñ 1019 cm-3, and the maximum mobility is 194 cm2/V-s. As increasing the Si dopant concentration, the near band edge photoluminescence emission peak intensity increases, but the full width at half maximum broaden from 47 meV to 117 meV. In Raman measurement result, with the increasing of Si dopant concentration, the E2(high) mode shifts from 569.4 cm-1 to 567.9 cm-1. The A1(LO) mode disappears gradually. In the nanodot growth, the AFM images show that the nanodots size become large as increasing the growth time. The nanodots size is change from 1.2 nm to 5.6 nm high and 40 nm to 110 nm wide, but the density of the nanodots decreases from 1.9 ¡Ñ 1010 cm-2 to 6 ¡Ñ 109 cm-2 at 15 sec and 90 sec growth, respectively. According to the AFM image of the nanodots surface morphology, the nanodots growth mode should be the Stranski-Krastanow mode.

Non-stoichiometric barium titanate (BaTiO3) powder of TiO2-excess compositions has been investigated using both reducing sintering and acceptor-doping. Crystalline phases were analysed by XRD. Attention has been paid to the analysis of the corresponding sintered microstructure by adopting scanning and transmission electron microcopy. Reducing sintering was in the low oxygen partial pressure, so as to dominate the oxygen-deficient. According to the defect chemistry, the purpose of acceptor-doping was the same as reducing sintering. We look out for phenomena which may be indicative that oxygen vacancies generated by acceptor-doping and reducing sintering have resulted in the metastable retention of high temperature hexagonal-BaTiO3 to an ambient temperature. In the Mg-doped study investigated the possibility that Mg2+ substitutes on Ti4+ site rather than the Ba2+ site, as expected from the radii. According to the unknown phase was indexed a supercell of MgTiO3, that showed evidence of Mg2+ dissolves in BaTiO3 and occupies the Ba2+ site. To reduce in a hydrogen atmosphere was a high dark conductivity. The Ti3+ content was determined via colorimetry. Because of the defect chemistry led to oxygen-deficient h-BaTiO3, i.e.BaTi1-xTixO3-x/2. The observed volume expansion behavior under Ar-H2 atmosphere demonstrates the possibility of having various microstructures via control of oxygen partial pressure. The transformation matrix described the relation between the two reciprocal lattices of the twinning. Investigation of reciprocal lattices was shown that ordering oxygen deficient on the BaO3 layer in the twin boundary. There was evidence of XRD patterns and surface energy that explained more and more twins in the microstructure via control of the low oxygen partial pressure. According to this theory, lamellae twins were generated by oxygen-deficient. The hexagonal phase might be also expressed as the cubic BaTiO3 containing twin boundary at BaO3 planes every three layers. That demonstrates the possibility of hexagonal phase retention in BaTiO3 was oxygen vacancies.