Structure and short-range order of vapour-deposited Si_1−xSn_x amorphous alloys

Abstract

Amorphous Si_1−x Sn_x alloy films have been prepared by the simultaneous evaporation of Si and Sn in high vacuum onto various substrates held at liquid nitrogen temperature. The structure of the alloys was investigated using scanning high-energy electron diffraction, density measurements and Mössbauer spectroscopy. For x<0·5, Sn atoms are shown to be substituted for Si, and selectively surrounded by Si atoms in almost perfect tetrahedral units, in a random continuous network. This trend of the alloys towards order can be traced to the size difference between Si (d = 2·35 Å) and Sn (d = 2·80 Å).