Physical Properties of Granular Metal Films and Their Applications for Electronic Devices

研究了Pt/SiO_2颗粒金属膜的电导率与温度的关系。当薄膜厚度足够薄时，在低温区观察到安德森局域化导致的金属-绝缘子转变。随着膜厚的增加，安德森局域化减弱，这种转变受到干扰。光化学能量转换粒状金属薄膜用于稳定半导体电极，用于光解水。对颗粒状金属包覆硅电极的光电化学性能进行了系统的研究，结果表明包覆硅电极可显著提高水分解反应的效率。Pt/TiO_2颗粒金属薄膜的电阻率受环境气体的影响较大：引入氢气使其电阻率降低，引入氧气使其电阻率升高。灵敏度与颗粒状金属膜中的金属含量有关。复合氧化膜研究了由不同中间体组成的二元和三元氧化膜。根据薄膜的红外吸收光谱研究，根据金属的相对离子半径不同，复合氧化物的晶体结构是氧盐型或双氧化物型。粒状半导体粒状性质扩展到半导体-绝缘体复合系统。尝试用各种方法制备分散在绝缘体薄膜中的半导体微粒。在Si/SiO_2颗粒状半导体体系中发现了一些光学吸收光谱的异常现象和吸收边的蓝移现象。

Electronic Transport Properties of Pt/SiO_2 Granular Metal FilmsTemperature dependence of the electrical conductivity of granular metals with intermediate metal contents( 40%) were investigated. Metal-insulator transition due to the Anderson localization was observed at low temperature region when the film thickness was thin enough. The transition was disturbed with increasing film thickness because of weakend Anderson Localization.Photo-Chemical Energy ConversionGranular metal films were utilized for stabilizing semiconductor electrodes for the photoelectrolysis of water. Systematic studies on the photoelectrochemical properties of the granular metal-coated Si electrodes revealed that the efficiency of the water decomposition reaction was improved signifcantly by the coating.Granular-Film Gas SensorThe electrical resistivity of Pt/TiO_2 granular metal films was found to be influenced strongly by ambient gases: The resistivity decreases by introducing hydrogen, whereas it increased by introducing oxygen. The sensitivities were dependent upon the metal fraction in the granular metal films.Complex Oxide FilmsBinary and ternary oxide films composed of various metas were investigated. According to the studies of infrared absorption spectra of the films, crystallographically preferable structure of the complex oxides was either an oxy-salt or a double oxide depending upon the relative ionic radii of the metals.Granular SemiconductorsThe granular nature was extended to semiconductor-insulator composite systems. Semiconducting fine particles dispersed in insulator films were tried to be fabricated with various methods. Some anomalies in optical absorption spectra as well as the blue-shift in the absorption edge were noted in a Si/SiO_2 granular semiconductor system.