Thin films are used in many energy conversion applications, ranging from photodetectors to solar cells. Accurately predicting the radiative properties of thin films when they possess rough surfaces is critical in many instances, but can be challenging due to the complexity arising from light scattering and interferences at the microscale. This work describes measurements of the spectral transmittance and reflectance of several thin-film materials (including crystalline silicon wafers and a polycrystalline diamond film) in the mid-infrared spectral region (2 20 m) using a Fourier-transform infrared (FT-IR) spectrometer. The transmittance and reflectance were calculated using thin-film optics for the double-side polished samples and scalar scattering theory for the single-side polished samples. The effects of partial coherence are considered using a fringe smoothing technique. The interval used for fringe smoothing was assumed to be linearly dependent on the wavenumber. Good agreement between the predicted and measured transmittance was achieved for the double-side polished silicon wafers and for the diamond film. The disagreement for some single-side polished silicon wafers may be inherently related to their surface microstructures, as suggested from surface topographic data and images obtained from surface profilometry and microscopy. By comparing the intervals used for fringe smoothing with the instrumental resolution, beam divergence in the spectrometer was found to be a major factor contributing to the partial coherence. Future research is proposed to investigate the correlation between the detailed surface characteristics and the conical-conical transmittance and reflectance.

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I have explored the use of the matrix assisted pulsed laser evaporation (MAPLE) and MAPLE direct write (MDW) to create thin films of biological materials. MAPLE is a novel physical vapor deposition technique used to deposit thin films of organic materials. The MAPLE process involves the laser desorption of a frozen dilute solution (1-5%) containing the material to be deposited. A focused laser pulse (~200 mJ/cm2) impacts the frozen target, which causes the solvent to preferentially absorb the laser energy and evaporate. The collective action of the evaporated solvent desorbs the polymeric solute material towards the receiving substrate placed parallel and opposite to the target. The bioresorbable polymer PDLLA and the anti-inflammatory pharmaceutical dexamethasone were processed using MAPLE, and characterized using Fourier transform infrared spectroscopy, atomic force microscopy and x-ray photoelectron spectroscopy. MDW is a CAD/CAM controlled direct writing process. The material to be transferred is immersed in a laser-absorbing matrix or solution and coated onto a target or support positioned microns to millimeters away from a receiving substrate. Using a UV microscope objective, a focused laser pulse is directed at the backside of the ribbon, so that the laser energy first interacts with the matrix at the ribbon/matrix interface. This energy is used to gently desorb the depositing material and matrix onto the receiving substrate. I have deposited neuroblasts within a three-dimensional extracellular matrix. These two laser processing techniques have enormous potential for functional medical device and tissue engineering applications.

As the minimum feature size in complementary metal-oxide-semiconductor (CMOS) devices shrinks, the leakage current through the gate insulator (silicon oxide) will increase sufficiently to impair device operation. A high dielectric constant (k) insulator is needed as a replacement for silicon oxide in order to reduce this leakage. Hafnium-based materials are among the more promising candidates for the gate insulator, however, it is hampered by material quality and thus has been slow to be introduced into high volume integrated circuit production. Hafnium oxynitride films are deposited by Metalorganic Chemical Vapor Deposition (MOCVD) and downstream microwave Plasma Enhanced Chemical Vapor Deposition (PECVD) employing different oxidants including O2, N2O, O2 plasma, N2O plasma, N2O/N2 plasma, and O2/He plasma in the current research. The effects of oxidants on deposition kinetics, morphology, composition, bonding structure, electrical properties and thermal stability of the resultant films each are investigated. The possible chemical/physical causes of these observations are developed and some mechanisms are proposed to explain the experimental results. Oxygen radicals, which are known of present in oxidizing environments are determined to play an essential role in defining both structures and the resultant electronic properties of deposited hafnium oxynitride films. This systematic investigation of oxidant effects on CVD grown hafnium oxide/oxynitride layers, in the absence of post-deposition annealing, provides new understanding to this area with potential importance to the integrated circuit industry.

Reducing fabrication and operation costs while maintaining high performance is a major consideration for the design of a new generation of solid-state ionic devices such as fuel cells, batteries, and sensors. The objective of this research is to fabricate nanostructured materials for energy storage and conversion, particularly porous electrodes with nanostructured features for solid oxide fuel cells (SOFCs) and high surface area films for gas sensing using a combustion CVD process. This research started with the evaluation of the most important deposition parameters: deposition temperature, deposition time, precursor concentration, and substrate. With the optimum deposition parameters, highly porous and nanostructured electrodes for low-temperature SOFCs have been then fabricated. Further, nanostructured and functionally graded La0.8Sr0.2MnO2-La0.8SrCoO3-Gd0.1Ce0.9O2 composite cathodes were fabricated on YSZ electrolyte supports. Extremely low interfacial polarization resistances (i.e. 0.43 Wcm2 at 700¡ãC) and high power densities (i.e. 481 mW/cm2 at 800¡ãC) were generated at operating temperature range of 600¡ãC-850¡ãC. The original combustion CVD process is modified to directly employ solid ceramic powder instead of clear solution for fabrication of porous electrodes for solid oxide fuel cells. Solid particles of SOFC electrode materials suspended in an organic solvent were burned in a combustion flame, depositing a porous cathode on an anode supported electrolyte. Combustion CVD was also employed to fabricate highly porous and nanostructured SnO2 thin film gas sensors with Pt interdigitated electrodes. The as-prepared SnO2 gas sensors were tested for ethanol vapor sensing behavior in the temperature range of 200-500¡ãC and showed excellent sensitivity, selectivity, and speed of response. Moreover, several novel nanostructures were synthesized using a combustion CVD process, including SnO2 nanotubes with square-shaped or rectangular cross sections, well-aligned ZnO nanorods, and two-dimensional ZnO flakes. Solid-state gas sensors based on single piece of these nanostructures demonstrated superior gas sensing performances. These size-tunable nanostructures could be the building blocks of or a template for fabrication of functional devices. In summary, this research has developed new ways for fabrication of high-performance solid-state ionic devices and has helped generating fundamental understanding of the correlation between processing conditions, microstructure, and properties of the synthesized structures.

Metallic honeycomb structures are being studied for use as thermal protection systems for hypersonic vehicles and as structural panels in other aerospace applications. One potential concern is the growth of fatigue cracks in the thin face-sheets used for these structures. To address this concern, the fatigue behavior of thin aluminum base alloy sheets ranging from 30 m to 250 m in thickness was investigated. The effect of material roll direction was also considered at 30 m. In all cases, the fatigue crack growth rates were found to be one to two orders of magnitude higher than that of the same material of greater thickness. In addition to data for fatigue crack growth rate, data are also presented for the effect of thickness on the fracture toughness of these materials.

Non-volatile memory is slower than DRAM (Dynamic Random Access Memory) but faster than HDD (Hard Disk Drive). In addition, compared to volatile memory, the non-volatile memory can retain stored information without power, and consume only low power. These characteristics show its popularity of flash memory built in portable devices. Currently the non-volatile memory applies the polysilicon and SONOS structure as floating gate, however, the new technologies of nanocrystal non-volatile memory are processed at high temperature. The manufacturing cost is rather high, so the process at lower temperature is very necessary. In this work, mixed zinc and silica amorphous layers are applied as floating gate to construct nano thin film non-volatile memory devices. The process does not need high temperature to form crystalline, and the defects in zinc oxide can be applied for charge storage. Supercritical carbon dioxide (SCCO2) treatment has been studied for the passivation of dielectric and reducing the activation energy. Using this low-temperature SCCD process ZnO nanocrystal can be formed, and the feasibility of fabricating nanocrystal NVMs device with low temperature SCCO2 is possible. The nonvolatile memory devices with Zn nano thin film embedded in MIS structure are performed. From C-V measurement, it is found that defects in SiO2 are repaired after 500¢J annealing. Because of the thermal diffusion, the storage layer SiO2/Zn-SiO2/SiO2 in device cannot be observed and the memory window disappears when the annealing temperature is higher than 700¢J. Therefore, the annealing process should be performed between 500¢J - 700¢J in making memory device. From DLTS analysis, a species with energy level of 0.6 eV is found in the as deposited Zn-SiO2 layer. After annealing in Ar, a new energy level 0.47 eV is found, and which shifts to energy level 0.85 eV after annealing in O2. In comparison to XPS results, traps of Zn-SiO2 exist before annealing, and after annealing in Ar, Zn-SiO2 transforms into Zn-O-Si. Traps of ZnO-SiO2 have been found after annealing in O2, which increases the memory effect with a 2 Volt memory window, so that more charges can be stored in the deep level traps of ZnO-SiO2 in the storage layer.

Polycrystalline Cu(In,Al)Se2 films were deposited by four-source evaporation of Cu, In, Al, and Se using Knudsen type sources in which the elemental fluxes were coincident onto soda lime glass substrates. The single-phase films with composition of Cu:In:Al:Se = 28:15:9:48 which were confirmed by X-ray diffraction and micro-Raman spectroscopy were deposited at substrate temperature of 560¢J. Secondary phases were observed when temperature of substrate is below 560¢J due to incompletely reaction. Under fixed effusion flux, the value of Cu/(In+Al) becomes larger as temperature of substrate increase. However, the value of Al/(In+Al) keeps nearly constant as temperature increase. The band gap is 1.53 eV derived from the result of spectrophotometer. The room temperature resistivity, Hall mobility and carrier concentration of the films are 0.28 £[cm, 24.63 cm2V-1s-1 and 1.27x1019 cm-3 respectively. And the conductive type is p-type. By the way, we try to grow Cu(In,Al)Se2 film in the presence of an Sb beam at substrate temperature of 440¢J. After the addition of an Sb beam, surface morphology become smooth and compact, but there is no significant grain growth. No matter an Sb beam adds or not, secondary phases were observed in both case due to the low temperature of substrate.

Since the first discovery of amorphous alloys in 1960, researchers have explored many unique mechanical, magnetic, and optical characteristics of such materials for potential applications. Up to now, well-developed processes, such as rapid quenching, sputtering, evaporation, pulse laser deposition, etc, have been applied for different applications in micro-electro-mechanical systems (MEMS). Due to the lack of ordered structure, amorphous alloys can bear a high stress in the elastic region. Their plastic deformation stability is also of interest and has been widely studied. The shear-band characteristic, a kind of inhomogeneous deformation mechanism, dominates the deformation after yielding at room temperature. While a shear band nucleate, its propagation usually cannot be arrested or stopped. In other words, the occurrence of matured shear bands needs to be prevented. There are two major approaches in this aspect. The first is to increase the material yield strength so as to delay the shear band nucleation. Another is to incorporate intrinsic or extrinsic particles so as to absorb the kinetic energy of shear bands in the amorphous matrix. In this study, we utilize three strategies to control the propagation of shear bands in thin film metallic glasses (TFMGs): sub-Tg annealing, the addition of strong element in solute form, and the introduction of strong nanocrystalline layers. For sub-Tg annealing, the base alloy system is Zr69Cu31, with a base film hardness of 5.1 GPa measured by nanoindentation. After annealing, the hardness exhibits ~30% increase. Without the occurrence of the phase transformation, as confirmed by X-ray diffraction, the possible reaction during sub-Tg annealing is attributed to structural relaxation, not crystallization. The full width at half maximum of the X-ray peak exhibits a decreasing trend in the using X-ray and transmission electron microscopy diffraction, meaning the excess free volumes forming during vapor-to-solid deposition process would be annihilated by localized atomic re-arrangement. Moreover, the formation of medium-ordering-range clusters was confirmed utilizing high-resolution transmission electronic microscopy. The denser amorphous structure leads to the increment of hardness. For the addition of Ta in Zr55Cu31Ti14, sputtering provides a wide glass forming range with solubility of Ta approaching ~75 at%. With increasing Ta content, the elastic modulus and hardness increase slowly. A steep rise occurs at ~50 at% of Ta. Up to 75 at% of Ta, the elastic modulus and hardness approaches 140 GPa and 10.0 GPa, respectively (100% increment). Up to now, Ta-rich TFMGs exhibit the highest elastic modulus and hardness among all amorphous alloys fabricated using vapor deposition techniques. The irregular increase is attributed to the formation of Ta-Ta bonding. A large quantity of Ta bonds would lead to the formation of Ta-rich nanoclusters, drastically decreasing the strain rate while shear band propagates under nanoindentation and microcompression tests. The introduction of nanocrystalline Ta layers can not only effectively enhance the yield strength but also serve as the absorber for the kinetic energy of shear bands, revealing ductility in the microcompression test.

Abstract In this study, copper oxide thin films prepared by DC reactive magnetron sputtering using a Cu target were studied. By changing the oxygen partial pressure ratios and sputtering power and deposition temperatures during sputtering, we obtained copper oxide thin films with different properties. The structures of copper oxide thin films were characterized by glancing incident angle X-ray diffraction. Clear crystal orientation at (002) plane were observed at 50% and 60% oxygen partial pressure ratio. The preferred orientation at (111) plane were observed with heating substrate to 200¢J. The optical and electrical properties of cupric oxide thin films were measured by UV-VIS spectrophotometer and four-point probe system. The cupric oxide thin films deposited with heating substrate to 200¢J exhibited the resistivity of 0.77£[-cm and optical band gap of 1.57 eV. Keywords¡G cupric oxide, thin film, magnetron sputtering, band gap