Observation of phase separation in Hg1?xCdxTe solid solutions by low incident angle x-ray diffraction

The low incident angle (surface analysis) and the conventional wide angle (bulk analysis) x-ray diffraction techniques were employed to investigate the existence of a miscibility gap in the Hg_1−xCd_xTe system. Samples of initial composition Hg_0.46Cd_0.54Te were annealed at 140 and 400°C, respectively, for four weeks. The diffraction planes (531) and (642) have been selected for the x-ray diffraction analysis. The results of this work provide the first, direct experimental evidence for the existence of a miscibility gap at lower temperature in the Hg_1−xCd_xTe system. The phase separation occurs primarily in a thin surface layer at 140°C and is reversible after annealing at 530°C. The compositions of the two compounds at the tie-line at 140°C are Hg_0.22Cd_0.78Te and Hg_0.63Cd_0.37Te.