Formation Conditions and Structure of Thin Epitaxial Germanium Films on Single-Crystal Substrates

Abstract

An experimental investigation of the effects of formation conditions on the structural characteristics of thin Ge films vacuum deposited onto synthetic single crystals of CaF2, NaCl, NaF, and MgO is reported. Formation conditions include substrate temperature during deposition, rate of deposition, and heat treatment. The amorphous to crystalline transformation of Ge was found to occur in the 300–350°C substrate temperature range. It is shown that single-crystal films, 1500 Å thick, can be formed on CaF2 substrates at temperatures between 450° and 700°C by proper choice of rate of deposition. Crystalline structure, porosity, complexity of imperfections, and film adhesion are dependent on the rate of deposition and deposition temperature.