Thermophysical Properties of Semiconductors

Abstract

The thermophysical properties of melts of samples from the Si-Ge system were measured in the Electromagnetic Levitator on board of the International Space Station (ISS-EML). The containerless measurements of the density, thermal expansion, surface tension, viscosity, and electrical resistivity were performed with highly doped samples in the stable melt as well as in the undercooled state. The volume and the electrical resistivity show a nonlinear temperature dependence. This behavior can be interpreted in terms of a structural change (phase transition) in the melt. With decreasing temperature, covalent, tetrahedral structure elements (small range order) begin to form, and therefore, the specific volume deviates from that of a simple liquid, which is characterized by a simple two-body interatomic potential with linear thermal expansion, leading to the observed nonlinear temperature dependence. The surface tension was investigated with the oscillating drop technique. The data are comparable to previous measurements and are only slightly temperature dependent. The surface oscillations are exponentially damped. The damping is dominated by turbulent flow in the melt.