Research of Metal-Nonmetal Transition of Electron-Hole System under Size Quantization in Bi in Strong Magnetic Field

采用真空蒸发技术在BaF_2单晶（111）面衬底上制备了铋薄膜。为了改善由于Bi和BaF_2之间晶格常数失配约3.6%而引起的薄膜退化，在略低于熔点（273 ℃）的温度下进行热处理。通过X射线衍射分析，证实薄膜为单晶，并具有垂直于衬底表面的择优取向。实验结果如下：（1）在BaF_2单晶衬底上，在80 ℃左右成功地制备了Bi薄膜。(2)对140 ~ 2800 μ m不同厚度的薄膜，均得到了平整的表面，并有分层生长。(3)在140 ~ 2800 μ m的厚度范围内，电输运的厚度和温度依赖性都存在经典的尺寸效应。(4)还证实了以布罗意波长为周期的尺寸量子化。(5)在420* 和560* 之间的载流子厚度依赖性中证实了金属半导体转变。

By a vacuum evaporation technique, bismuth thin films were prepared on BaF_2 single crystal substrate with (111) surface. To improved the degradation of films due to a misfiting of the lattice constant between Bi and BaF_2 by about 3.6%, the heat treating was carried out at a temperature just below the melting point(273ﾟC). By X ray analysis, it was confirmed that the films were single crystal and had a preferred orientation perpendicular to the surface of the substrate. The experimental results are summarized as follows :(1) Bi thin films were prepared reproducibly on BaF_2 single crystal substrate at around 80ﾟC.(2) Flat surface with layring growth were obtained for films with different thickness from 140*to2800*.(3) A classical size effect was confirmed for the thickness and temperature dependence of electrical transport for the films with different thickness from 140* to 2800*.(4) The size quantization with a period of de Broglie wave length was also confirmed.(5) The metal semiconductor transition was confirmed in the thickness dependence of carriers between 420* and 560*.