Self‐Diffusion in Selenium

Abstract

Self‐diffusion measurements have been carried out in single crystals of the semiconductor element selenium using a residual activity method and Se‐75 as the tracer in the temperature range 152 to 215 °C. In the direction of the trigonal axis (| c‐axis) the data of the lattice diffusion can be represented by D⟂ = 0.2 exp (—1.2 eV/kT) cm² s⁻¹. The diffusion along the short circuit paths can be approximately described by the values Q≈︁ 0.5 eV and Q≈︁ 0.7 eV for the activation energy and by diffusion coefficients between 5 × 10⁻¹⁰ and 10⁻⁸ cm² s⁻¹ in the temperature range considered. The vacancy formation enthalpy in selenium is estimated to be about 0.75 eV. From the diffusion data determined the vacancy migration enthalpy is estimated to be about 0.5 eV along the c‐axis and 0.7 eV perpendicular to the c‐axis. It is possible to explain the self‐diffusion in selenium on the basis of a vacancy mechanism. The anomalous self‐diffusion behaviour of the elemental semiconductors and correlation considerations are discussed. Several typical features were found and the presented results for selenium are shown to be in agreement.