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Non-evaporable getters (NEG) are widely used in ultra high vacuum (UHV) systems for particle accelerators to assure distributed pumping speed. By heating the NEG to an activation temperature, the oxide layer on the surface dissolves into the material, leaving a clean (activated) surface. The activated NEG surface is capable of chemisorbing most of the residual gases present in a UHV system and will act as a vacuum pump. NEG can be sputter deposited on the inner wall of vacuum chambers, turning the whole wall from a source of gas into a pump. At the largest particle accelerator in the world, the Large Hadron Collider, more than 6 km of beam pipe has been NEG coated. In this work, a DC magnetron sputtering system dedicated for coating cylindrical vacuum chambers with NEG has been assembled, installed and commissioned. The system has been used to do NEG depositions on inner walls of vacuum chambers. The vacuum performance of the coating has been measured in terms of pumping speed, electron stimulated desorption and activation temperature. In addition, the thin film composition and morphology has been investigated by scanning electron microscopy (SEM). The work has resulted in an operational DC magnetron sputtering system, which can be used for further studies of NEG materials and compositions.

For the shortage of energy and the environmental issues, the development of solar cells has become an important technology. However, solar cells have low efficiency of energy conversion due to their high surface reflection on a flat Si substrate which is 38 %. To decrease the surface reflectance of the silicon solar cells, anti-reflection coatings (ARCs) are proposed on the solar cells. We use Lighttools software to investigate several kinds of ARCs to decrease the surface reflectance. We first consider the reflectance of the single-layer ARC with quarter wavelength. It can effectively decrease about 30 % surface reflection as compared with a flat Si substrate. The half-cylinder texture and the wave texture are designed on a PMMA single-layer coating. It is found that the half-cylinder ARC and the wave ARC can usefully diminish the surface reflectance for perpendicular light. Low reflectance can be achieved in the hemispherical microlens ARCs over an extended spectral region for omnidirectional incident light. The impact of the microlens sizes, periods, and arrangements are investigated. The lowest normal reflectance of the closely-packed triangular-lattice hemispherical microlens ARC is 4.8%. By adding smaller hemispherical microlenses, the surface reflectance of the hemispherical microlens ARC can be as low as 1.86 %. To obtain the lowest average surface reflectance, both-sided patterned surface texture ARCs are designed. Their lowest average surface reflectance is 2.24%. Finally, we simulate the reflectance of the nanowire ARCs. The influence of the wire length and the angle of inclination are discussed for high-efficiency and low-cost solar cells.

Recently, with the escalating demands for optical communications, the need for bandwidth in optical communication network has increased. The technology fiber fabrication opens the possibility for fiber bandwidth form 1.3 to 1.6£gm. Cr4+:YAG double-clad crystal fiber (DCF) grown by the co-drawing laser-heated pedestal growth method has a strong spontaneous emission spectrum from 1.3 to 1.6£gm. Such fiber is therefore, eminently suitable for optical coherence tomography (OCT), broadband optical amplifier, amplifier spontaneous emission (ASE) light source, and tunable solid-state laser applications. In this thesis, multilayer dielectric thin films were directly deposited by E-gun coating onto the end faces of the Cr4+:YAG DCF. To improve thin-film quality, we can increase transmittance of laser output, and to design for the high power laser. For broadband optical amplifier in dual-pump and double-pass scheme, a 2.8-dB gross gain, a 1.6-dB insertion loss, and a 1.2-dB net gain at 1.4-£gm signal wavelength have been successfully developed with HR coating onto one of the Cr4+:YAG DCF end faces.

High-resolution and low-cost fabrication techniques are essential for nanotechnology to overcome the commercialization barrier to benefit our society. Since its inception nanoimprint has become the ideal technology to fabricate dense sub-micron structures over large areas with low cost, which are important to many applications such as high-density storage disks and diffractive optical devices. The decade-long development in nanoimprint equipment has reached a point where large-scale manufacturing of high-density nanostructures are possible. However, there are a few remaining issues that need to be studied before the advent of commercial application of nanoimprint. In this work we look at a pressing issue, long-term stability of the mold surfactant coating. It is important to understand the details of the surfactant wear during nanoimprint in order to limit defect density to a tolerable threshold in a high-volume manufacturing process. To study this we went through a nanoimprinting procedure and measured chemical and physical alterations in the coating. The surfactant wear information also helps to optimize the time interval for surfactant recoating to keep the fabrication throughput as high as possible. In this paper we characterize the stability of two commonly used surfactants as well as prescribe a new technique for mold anti-adhesion. Through this work we see that FDTS and OTS undergo significant degradation in air and gradual degradation by chain scission is observed during the nanoimprint procedure. It is also noted that an embedded anti-adhesion layer is effective for mold releasing.

The thesis consists of two aspects: (1) Research on regrowth by molecular beam epitaxy, and (2) Silicon monoxide coating. In part one, we used (NH4)2Sx to passivate the InAlGaAs/InP surface. From the X-ray photoelectron spectroscopy (XPS), the passivated surface shows a dramatic reduce of oxidation. A preparation chamber for the regrowth has been setup to proceed the sulfur passivation method. We can obtain a clean surface for regrowth after heating and putting samples in the high vacuum chamber. In the design of regrowth layers, we have found the best waveguide structure by regrowth. When the ridge width is 2.5 mm with etching depth 1.4 mm, a circular mode profile can be obtained by Fimmwave simulation. In the integration between devices, we have designed the best waveguide structure after regrowth by BeamProp 3D. The best design will make the propagation loss smaller than 0.21%. The second part is anti-reflection (AR) coating by silicon monoxide (SiO) deposition. The SiO refractive index of 1.8837 was obtained by transmission, and ellipsometer measurements. The corresponding AR coating thickness for InP substrate is 2057 &#x00C5;. In order to make AR coating on lasers of different effective index, we design the double-layer coating. For Beam Expander Semiconductor Optical Amplifier (BESOA), SiO2 / SiO and Si3NX / SiO double-layer coatings were compared with SiO single layer. The reflectance (R) was reduced 16.86 % and 25.12 %, respectively, and the R < 1% bandwidth extends 200 &#x00C5;.

Abstract This thesis studies the practical appraisal for pipeline inspection using the guided wave T(0,1) mode. The characteristic of reflected signals from the features of pipeline for various coated materials and fluid-filled pipes are also evaluated. The attenuation and the traveling distance of the guided wave are then calculated from the above-mentioned data for pipeline inspection in petro-chemical industries. In the experimental setup, the torsional mode is excited at one axial location using an array of transducers distributed around the circumference of the 6-inch test pipe. The reflected signals from various features, such as flanges, welds, supports, bends, defects and patches are analyzed at first at specific frequencies in the experiments. The effect of various coated material such as bitumen, PE and insulated material are also evaluated for the propagating torsional mode T(0,1) in the pipe. The results show that the attenuation of reflected signal is heavy for the bitumen-coated case because its viscosity is much higher than the other cases. Furthermore, the effect of pipe contents for defect detection using T(0,1) mode is investigated in this thesis. Various pipe contents, such as water, diesel oil, lubricant and fuel oil are deposit into the test pipe, respectively, to evaluate the influence to T(0,1). For the attenuation evaluation of reflected signal from flange in pipe, the reflected signal from an air-content pipe is measured for reference to compare with the measurements of other pipe contents in the experiments. The results show that the low viscosity liquid deposit in the pipe, such as water, diesel oil and lubricant, has no effect on the torsional mode; while the high viscous of the fuel oil deposit in the pipe attenuates the reflected signal heavily. It became evident that the torsional mode T(0,1) is most suitable for use in fluid-filled pipeline inspection.

ZnO (Zinc-oxide) is a wide bandgap (Eg~3.3 ev ) semiconductor material , it is transparent in the visible region of the spectra and therefore, also less light sensitive. ZnO-based TFT can increase the field mobility, improve the opening of AMLCD pixel and the problem of photo-excited leakage current. Here we demonstrate ZnO-based TFT which was fabricated by sol-gel material through spin-coating deposition method. The process of spin-costing deposition provides a more efficient way for depositing device components and low cost than vacuum techniques. In the experiment we controlled the conductive and carrier concentration by different annealing temperature and different annealing equipment for optimizing our device characteristic. The material analysis of ZnO film is discussed by FTIR, SEM, and n&k. The electrical characteristic was measured by the I-V measurement system.

Abstract Pool boiling process is frequently encountered in a number of engineering applications. However, it is difficult to exactly predict the heat transfer coefficient. This is because the boiling phenomenon is rather complex and influenced by many factors, such as surface condition, heater size, geometry, material, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure diameter, frequency and nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. The present study is ain at providing the pool boiling data for plasma coating and helical wire wrapped enhanced tubes. Furthermore, more fundamental of the physical phenomenon can be obtained. This study was performed experimentally. R-134a and R-600a were used as refrigerants. The surface condition will be changed with plasma spray coating and helical wire wrapped. It is expected that the surface condition can affect the nucleate boiling heat transfer in certain degree. In addition, boiling visualization was also made to broaden our basic understanding of the bubble diameter and dynamics while growing. Thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results will hopefully be helpful not only for the academia but for the industry.

Abstract Pool boiling process is frequently encountered in a number of engineering applications. However, it is difficult to exactly predict the heat transfer coefficient. This is because the nucleate pool boiling phenomenon is rather complex and influenced by many factors, such as surface roughness, areas of heater, material, geometry, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure frequency, diameter and active nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. This study was performed experimentally. R-134a was used as refrigerants, and the present study is aim at providing the pool boiling data for smooth and plasma coating enhanced tube bundles. It is expected that the surface condition, amount of test tubes, geometric of bundles and different heat flux can affect the nucleate boiling heat transfer in certain degree. In addition were calculated and developed that heat transfer coefficients and relevant corrections. Furthermore, more fundamental of the physical phenomenon can be obtained. According to the results of experiments, Boiling curves and calculations of the bundle factors and geometry factors were subsequently secured. The enhanced heat transfer coefficients with coated tube bundles are 1.1-2.0 times higher than smooth tube bundles. The 1.5-2.3 and 1.1-3.8 bundle factors obtained from the smooth tube bundles and coated tube bundles respectively. The geometry factors were about 1 for all arrangements studied herein. Thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results will hopefully be helpful not only for the academia but for the industry.