Thermal expansion of ZnTe and HgTe and heat capacity of HgTe at low temperatures

Abstract

The linear coefficient of thermal expansion of ZnTe and HgTe is measured between 1.5 and 30K by means of a three-terminal capacitance dilatometer; the heat capacity of HgTe is measured in this temperature range. Values gamma 0th=0.07+or-0.07 (ZnTe) and -1.2+or-0.2 (HgTe) are obtained for the zero-temperature limit of the Gruneisen parameter. The former value is in good agreement with gamma 0el=0.05 calculated from the pressure derivatives of the elastic moduli. The low-temperature limiting value of the Debye temperature theta 0th=147.5+or-2K for HgTe. The variation of gamma (T) and theta D(T) as functions of reduced temperature, T/ theta D, fit the patterns established previously for other II-VI compounds of zincblende structure.