On the theory of temperature shift of the absorption curve in non-polar crystals

Abstract

On the assumption that valence or conduction electrons move in a periodic potential field produced by ions oscillating around their equilibrium positions an expression is derived for the dependence of the temperature shift of the absorption curve for non-polar substances of diamond structure or with a ZnS type of crystal lattice. By a method analogous to the procedure in investigating the temperature dependence of the intensity of Laue-Bragg maxima for the diffraction of X-rays it is shown that for lower temperatures this dependence is at first quadratic, later linear and at high temperatures an exponential function of the temperature. It is proved that in contrast to previous theories the qualitative character of this dependence is in agreement with experience. It is shown that for diamond, silicon and germanium the numerical values are also of the same order as the measured values.