Materials Science Forum Vols. 475-479

Abstract: Fe films have been grown on different oriented Si substrates by metal organic chemical vapor deposition (MOCVD), and then samples are put in the air without any protection for nearly fifteen years. In this paper, using methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM), we make a detailed research on the samples. We identify the composition and structure of the epitaxial films on different oriented substrates and compare the difference both in composition and magnetic properties. Different orientation of the substrates results in different epitaxial film with different characteristic. We also confirm the existence of single crystal iron in the heteroepitaxial film grown on Si (001), and discuss the possible reason why the single crystal iron film still exists without complete oxidation in air for such a long time.

Abstract: In this paper, the influences of depositing angles on TbFe film magnetic and magnetostrictive characteristics were discussed. TbFe films were deposited by DC magnetron sputtering. With the decrease of depositing angles from 900 to 150, TbFe film in-plane magnetization measured at 1600kA.m-1 external field is greatly increased. With the decrease of depositing angles from 900 to 150, the magnetostrictive saturation field is decreased. TbFe film in-plane magnetostriction is improved when depositing angles are changed from 900 to 150. Magnetic domain structures detected by MFM indicates that film easy magnetization direction is gradually changed from perpendicular to parallel with the decrease of depositing angles. The variation of film magnetic and magnetostrictive performances can be explained by the oblique anisotropy associated with columnar grain morphology of the films.

Abstract: Transport properties of YBa2Cu4O8 (YBCO)/La0.67Ca0.33MnO3 (LCMO) multilayers were studied. The metal-semiconductor transition temperature shows an oscillatory behavior with a period ~ 12 nm. In contrast to that for LCMO films, the magnetoresistance ratio for multilayers is enhanced and strongly depends on the thickness of the YBCO layer. These results imply that the magnetic spin interaction between the LCMO layers may exist through the normal-conductive YBCO layer.

Abstract: ZnO thin film, as a promising piezoelectric material, possesses unique electrical, acoustical, and optical properties. In this paper, Al/ZnO thin film was deposited on Si wafer by magnetron sputtering. Highly oriented, dense, and fine-grain polycrystalline ZnO films with excellent surface flatness and high resistivities have been obtained, when the sputtered gas pressure was 0.9 Pa, the temperature was 200 °C and the Ar-to-O2 ratio was 1:3. A 780MHz surface acoustic wave filter (SAWF) has been successfully fabricated using the Al/ZnO film on silicon wafer.

Abstract: To obtain both high power durability and fine-dimensional control in high-frequency surface acoustic wave devices, a highly oriented (111) texture was developed in electronic beam evaporated Al films on Zr underlayer. In this paper, the effects of Zr underlayer on the microstructure and resistivity of Al/Zr/LiNbO3 films were investigated. The films show an extremely smooth surface. The optimum annealing temperature is 200 °C to obtain low resistivity. For Al films with Zr underlayer, reactive ion etching with gases containing BCl3 can be more easily performed than that for Al films with Cu underlayer.

Abstract: GaN films are grown on Si(111) with low-temperature GaN (LT-GaN) layers as buffer layers by hydride vapor phase epitaxy (HVPE). The LT-GaN layers are deposited at different temperatures ranging from 400 to 900 °C. The surface property, the structure and optical properties of the GaN films with different LT-GaN layers are studied. When deposition temperature of LT-GaN layer is 600 °C, the GaN film shows the best properties.

Abstract: One of the most challenging problems to develop polycrystalline silicon thin-film solar cells is the growth of crystalline silicon on foreign, low-cost and low-temperature substrates. In this paper, a laser doping technique was developed for the plasma-deposited amorphous silicon film. A process combination of recrystallization and dopant diffusion (phosphorous or boron) was achieved simultaneously by the laser annealing process. The doping precursor was synthesized by a sol-gel method and was spin-coated on the sample. After laser irradiation, the grain size of the doped polycrystalline silicon was examined to be about 0.5~1.0 µm. The concentrations of 2×1019 and 5× 1018 cm-3 with Hall mobilities of 92.6 and 37.5 cm²/V-s were achieved for the laser-diffused phosphorous- and boron-type polysilicon films, respectively.