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The purposes of this thesis are to prepare ZnO and tin-doped In2O3 (ITO) films at low temperature and study their microstructure and optoelectronic properties. Low-temperature growth of undoped ZnO films with high transparency and low electrical resistance was prepared by ion beam sputtering. After systematic testing, a sheet resistivity as low as 2.95 x 10-3 £[-cm was obtained at a substrate temperature of 150 oC, ion source voltage of 850 V, and ion beam current of 30 mA. The transmittance of the ZnO films was in the range of 85-90%. Hall measurements showed that a high mobility of 21.41 cm2/Vs was obtained for films less than 200 nm thick. The related microstructures and physical properties were measured and discussed. ZnO nanofilm of (2-1-10) and (01-11) surfaces were prepared on NaCl (001) surface at 200 oC and 400 oC to produce nearly pure (2-1-10) and (01-11) textures respectively and the orientation relationships were determined and the interface discussed. By dissolving the NaCl substrate, the ZnO (2-1-10) and (01-11) surfaces several cm2 in area, which may have some useful applications, can be easily prepared. The photoluminescence spectrum from the (2-1-10) surface showed only a near-band-edge UV emission peak while the (01-11) surface showed a near band-edge UV emission and a broad green emission. Low-temperature preparation of transparent conducting electrode is essential for flexible optoelectronic devices. ITO films of high transparency and low electrical resistance were prepared at room temperature with a radio-frequency ion beam sputtering system. Specimens with a low sheet resistivity of 10-4 £[-cm and a high visible-light transmittance of 85-90% were obtained. Hall measurement was used to measure the mobility and carrier concentrations and the effects on resistivity were discussed. ITO films were deposited on glass substrates at 200 oC at various oxygen flow rates. At low oxygen flow rate the film surface has ITO whiskers with metallic In tips and a crystallographic relationship of (010)In//(110)ITO and (001)In//(001)ITO is present between them. The In tips act as the seeds for the growth of ITO whiskers by a vapor-liquid-solid growth mechanism. As the oxygen flow rate increases, the crystallinity of the ITO film decreases till an amorphous phase is formed. The microstructure, resistivity and transmittance of the films were studied as a function of oxygen flow rate. Thin films of high transmittance (~90%) and low resistivity (6 x 10-4 Ω-cm) were prepared at an intermediate oxygen flow rates.

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Aluminum nitride (AlN) thin film is a promising material as buffer layer in GaN-based optoelectronic and electronic devices or as a substrate to fabricate Surface Acoustic Wave (SAW) and Film Bulk Acoustic wave Resonant (FBAR) devices in high frequency in wireless (>1GHz) communication technology. Aluminum nitride, thin film with the c-axis normal to the film is favored in a low energy deposition condition because it places the packed hexagonal basal plane parallel to the substrate surface. Grains of this orientation have a low surface energy which favors rapid growth in a columnar structure. In this experiment r.f. dual ion beam sputtering (DIBS) system is used to prepare the AlN films on Si (100) substrate. Various processing variable were tested to deposit AlN films with desirable properties. After systematic testing, a high quality film with preferred c-axis orientation was grown successfully on Si (100) substrate with Al target under the process parameters of 700 ev energy flux; 55% N2 / (N2+Ar) ratio; 4X10 - 4 torr working pressure with no heating of substrate. The AlN target is also used. The results show the great sensitivity of the films to oxygen-containing environments. Only under low residual oxygen pressure, could aluminum nitride be grown well. The deposited AlN thin film characteristic were studied by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Electron Spectroscopy for Chemical Analysis (ESCA).

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Nanocrystalline £\-Zr condensates deposited by ion beam sputtering on the NaCl (100) surfaces and then annealed at 100 ¢J to 750 ¢J in air. The phases present were identified by transmission electron microscopy to be nanometer-size £\-Zr+ZrO¡B£\-Zr+ZrO+c-ZrO2¡Bc-ZrO2¡Bc-+t-ZrO2¡Bt-ZrO2¡Band t-+m-ZrO2 phase assemblages with increasing annealing temperature. The zirconia showed strong {100} preferred orientation due to parallel epitaxy with NaCl (100) when annealed between 150 ¢J and 500 ¢J in air. The c- and t-zirconia condensates also showed (111)-specific coalescence among themselves. The c- and/or t-ZrO2 formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of the neighboring grains. (Part 1) Nanocrystalline £\-Zr condensates were deposited on the NaCl (100) plane at 25 to 450 ¢J by radio frequency ion beam sputtering from a pure 99.9¢H Zr disk. The nano condensates were identified by transmission electron microscopy to be quasiamorphous, £\-Zr, £\-Zr+ZrO and £\-Zr+ZrO+c-ZrO2 phase assemblages with increasing substrate temperature. At 400 ¢J and under 1-20 sccm oxygen, c- and t-ZrO2 nanocondensates were assembled on NaCl (100) as monolayer nanocrystalline material and showed strong preferred orientation. The c- and/or t-ZrO2 were retained by small grain size, low-valence Zr cation and 2-D matrix constraint of the film. (Part 2) Nanosized c- and t-ZrO2 were formed as monolayer nanocrystalline film on NaCl (100) plane by radio frequency ion beam sputtering. The microstructure and the epitaxy relationship with the NaCl (100) plane were studied by a high resolution transmission electron microscope. The epitaxy orientation was found to be [001]Z//[001]N, [100]Z//[1 0]N (group A), and [011]Z//[001]N, [100]Z//[100]N (group B) between zirconia (Z) and NaCl (N). Group B has two variants and is the dominant type. The possible causes for the epitaxy relationship are discussed. Crystallites within the same group can merge by rotation and coalesce into a single crystal, whereas crystallites in different groups can form high-angle grain boundaries. (Part 3) Special interfaces were formed for the c- and/or t-ZrO2 (Z) nano-crystals when deposited on the NaCl (N) (100) cleavage plane by ion beam sputtering to follow the epitaxy relationships of [001]Z//[001]N, (100)Z//(1 0)N (group A); and [011]Z//[001]N, (100)Z//(100)N (group B1) or (100)Z//(010)N (group B2). The nanoparticles in group A and B were impinged and coalesced to form {220}A/{200}B and {200}A/{111}B interfaces; with anchored dislocation whereas those in group B1 and B2 form {220}B1/{200}B2 interface. The {220}A/{200}B interface is found to be of especially low energy due to good match O2¡V lattice sites, and smoothly joints {200} and {220} planes across the interfaces without mismatch strain and dislocations. The special interfaces may shed light on the epitaxial mechanism of nanocrystalline materials in general. (Part 4)

Abstract Recently, titanium dioxide¡]TiO2¡^ is one of the most extensively studied transition-metal oxides because of its remarkable photocatalyst efficiency and electronic properties. In this paper, thin films ware obtained by dual ion beam sputtering. By different processes, these samples can be classified into three categories. Firstly, thin films, deposited on 200 mash copper grids for 15 minutes, were investigated that many TiO grains is about 5 nm in size by transmission electron microscopy¡]TEM¡^. Next, TiO2 thin films, sputtered on si wafers and glass for 180 minutes in an O2 environment by using titanium target, were initially identified by X ray diffraction instrument¡]XRD¡^. The result shows that some thin films have good orientations. By TEM, TiO2 grains on bottom of films are about 20 nm. By scanning electron microscopy¡]SEM¡^, TiO2 grains on the surface are about 1~2 £gm in size and are oblong in shape. The last, TiO thin films were directly deposited on si wafer for 180 minutes in no O2 environment by using titanium target and then annealed to transform from TiO to TiO2. By XRD, the thin film, annealed at 600¢J for 1hr, has good orientation. By TEM, TiO2 grains, annealed at 1000¢J for 24hr, grow up to 1-2 £gm in size and are oblong in shap.