Temperature dependence of tetragonal distortion and thermal expansion of copper indium selenide

Abstract

Accurate lattice parameters of chalcopyrite semiconductor copper indium selenide (CuInSe2) have been determined as a function of temperature by X-ray powder diffraction method in the temperature range 28 to 566 degrees C. The data have been used to evaluate the coefficients of thermal expansion alpha perpendicular to and alpha /sub ///, perpendicular and parallel to the principal axis, at various temperatures by a graphical method. The average thermal expansion coefficients, alpha perpendicular to and alpha /sub ///, thus evaluated in the temperature range 28 to 566 degrees C are found to be 10.32*10-6 K-1 and 7.89*10-6 K-1. This result indicates an 'increase' in tetragonal distortion (2-c/a) with temperature. An attempt is made to explain the temperature dependence of the anisotropic thermal expansion and the tetragonal distortion of this compound, in terms of the thermal expansion of the I-VI and II-VI bonds.