Studies of metal-semiconductor transition by using a newly developed desk-top-type high-rate sputtering apparatus

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Major results obtained in the last two years are summarized below.1. A desk-top-type DC high-rate sputtering apparatus is designed and constructed with the following concepts : a target is only 30 mm in diameter and, hence, is small enough to be prepared by arc-melting in our laboratory and an amorphous film as thick as 0.5 mm can be deposited within 3 days in a continuous automatic operation mode. The construction of the apparatus has completed at the end of the first year of this project, March 1991.2. Its performance has been tested in 1992. After various adjustments and test, we have reached a stage which fulfills all of our originally proposed requirements.3. The amorphous V_<50>Si_<50> films of 0.3 mm thick can be formed using this newly built sputtering apparatus. The atomic structure has been investigated by X-ray and neutron diffractions. The results are now subjected to a comparison with the data for amorphous alloys synthesized by other techniques like mechanical alloying. Measurements of the low-temperature specific heat and the electrical resistivity have also started. More data are being accumulated.4 The electron transport mechanism of metallic glasses and quasicrystals in the metal-semiconductor regime has been investigated. We could analyze all data consistently in a unified picture, using as critical parameters the electron diffusion coefficient D and the so called g-factor, which is defined as the ratio of the density of states at the Fermi level over the corresponding free electron value. It is also realized that further accumulation of data about the atomic and electronic structures near the metal-insulator transition regime is of urgent necessity. Our newly built apparatus will promise us to furnish these fundamental data.