A comparison of force constants, mechanical and thermal properties in Hg_1−xCd_xTe and Hg_1−xZn_xTe mixed crystals

Abstract

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.

Determination of HgCdTe elasto-plastic properties using nanoindentation

“…The root-mean-square roughness values, R rms , evaluated over a surface area of 0.5 3 0.5 mm 2 that were obtained with the aid of scanning probe microscope images have confirmed a significantly rougher surface for the bulk HgCdTe (R rms, bulk % 3.5 nm) in comparison to LPE and MBE grown HgCdTe (R rms, MBE/LPE % 0.3 nm). 19 and previous E avg values measured for Bridgman grown bulk Hg 0.8 Cd 0.2 Te. 17 The experimental E avg values agree with the E Voigt average because the isostrain Voigt model is more appropriate than other average modulus models since as the nanoindentation tip deforms the crystal surface it induces strains locally, which result in nearly uniform strains around dislocations.…”

“…The hardness of bulk HgCdTe has been the topic of significant research: [8][9][10][11][12][13][14][15][16][17][18] however, investigations of the parameter that determines the mechanical performance of the material, that is the modulus of elasticity, are very limited for HgCdTe. 17,19 The mechanical properties of bulk materials as well as thin films are increasingly being determined using depth sensing indentation (DSI), [20][21][22][23][24][25] which is (Received October 17, 2005; accepted January 19,2006) generally referred to as nanoindentation. The main advantage of this method in the determination of material mechanical properties lies in the fact that no special sample shape or preparation is necessary.…”

Mechanical and Thermal Properties

“…Alternatively, one could assume reasonable elastic coefficient variations that are consistent with the composition dependence of the bulk modulus, as presented by Bagot et al . [71]. The authors present a nonsymmetric sinusoidal bulk modulus variation at 80 K, such that as x increases from zero a decrease in the bulk modulus value occurs reaching a [44] minimum of 1% lower than that for HgTe (E HgTe ≈ 46.5 GPa) near x = 0.1.…”

Optical Properties

“…The IR optical properties of Zn x Hg 1Àx Te have been studied by a number of authors [261][262][263][264]. The absorption coefficients a(E) in the fundamental absorption edge of Zn x Hg 1Àx Te have also been measured by several authors [264][265][266].…”

“…The optical properties in the reststrahlen region of Cd x Hg 1Àx Te have been investigated by a number of groups [263,[268][269][270][271]. The a(E) spectra in the IR region have also been measured by a number of authors [272][273][274][275][276][277][278].…”