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

现将过去两年取得的主要成果总结如下：设计和制造了一台台式直流高速溅射装置，它的概念是：靶的直径只有30 mm，因此小到可以在我们实验室用电弧熔化的方法制备，并且可以在连续自动操作模式下在3天内沉积出厚度为0.5 mm的非晶膜。该装置的建造已于本项目第一年结束时完成，1991.2年3月。它的性能在1992年进行了测试。经过多次调整和测试，我们已经达到了最初提出的所有要求的阶段。用这套新研制的溅射装置可以制备0.3 mm厚的非晶态V_(50)；Si_(50)；50&gt；薄膜。用X射线和中子衍射法研究了它的原子结构。现在将结果与通过机械合金化等其他技术合成的非晶态合金的数据进行比较。低温比热和电阻率的测量也已经开始。更多的数据正在积累中。4研究了金属玻璃和准晶在金属-半导体区域的电子输运机制。我们可以在统一的图像中一致地分析所有数据，使用电子扩散系数D和所谓的g因子作为关键参数，g因子被定义为费米能级上的态密度与相应的自由电子值的比率。人们还认识到，迫切需要进一步积累关于金属-绝缘体过渡区域附近的原子结构和电子结构的数据。我们新建造的仪器将向我们承诺提供这些基本数据。

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.