A study of the local atomic structure in Hg0.80Cd0.20Te using x-ray diffuse scattering

Abstract

The local atomic arrangements in a commercial n-type wafer of Hg0.8Cd0.8Te were investigated by measuring the diffuse x-ray scattering in two volumes in reciprocal space. A change in contrast between the two measurements was achieved by making one volume measurement at 12037 eV and a second volume measurement at 12270 eV, i.e., near the HgLIII edge. The difference between these two measurements yielded intensity only due to Hg–Hg, Hg–Te, and Hg–Cd pair interactions. In all three patterns, peak-like features were apparent at the forbidden Bragg peak positions on thermal diffuse scattering ridges that joined major Bragg reflections; these are primarily attributed to second order displacement effects on the mixed cation sublattice. The first two Warren–Cowley short-range order parameters were determined to be α½½0 = −0.050(26) and α110 = 0.118(35). Simulations of the structure revealed small ordered regions with a preference for 3:1 Hg–Cd near-neighbor configurations. The near-neighbor Hg–Te bonds contract from that calculated from the average crystal's lattice parameter, and this Hg–Te distance is less than the distance in HgTe.