The thermal expansion coefficient variations in Hg, -.Cd,Te (MCT) and Hg, -,Zn,Te (MZT) are analyzed between 4 and 280 K. The phonon density of states (DOS) is modelled with seven Einstein peaks whose weight is adjusted to fit the specific heat variations. The mean Gruneisen coefficient associated with each peak is then deduced from a fit of the experimental linear thermal expansion coefficients. The variation with x of these Gruneisen coefficients allows to compare the bond strengths in MCT and MZT. A better stability of MZT as compared to MCT is deduced.
Interatomic force constants are deduced from a fit of infrared reflectivity data of HgCdTe (MCT) and HgZnTe (MZT) mixed crystals using a basic unit model for the description of vibrational modes of low wave vector. This allows, for the first time, a direct comparison of bond strengths between MCT and MZT. The obtained results are consistent with a slight decrease in bond strength when Cd is substituted for Hg in MCT and an increase when Zn replaces Hg in MZT. These results are visualized through the bulk modulus variations with composition in both mixed crystals and are compared to known results on their thermal properties.
Specific heat measurements have been performed on Hg,,,Zn,,,Te at low temperatures. C, experimental results can be described by the interpolation of t h e Cvs of the end binaries HgTe and ZnTe, A comparison with results on HgCdTe show that the 0 K Debye temperature of HgZnTe is higher than that of HgCdTe having,the same energy gap. Experimental C, results can be modelled with a simple phonon density of states in these mixed crystals.
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