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 an gle (bulk analysis) x-ray diffraction techniques were employed to inve stigate the existence of a miscibility gap in the Hg1-xCdxTe system. S amples of initial composition Hg0.46Cd0.54Te were annealed at 140 and 400-degrees-C, respectively, for four weeks. The diffraction planes (5 31) and (642) have been selected for the x-ray diffraction analysis. T he results of this work provide the first, direct experimental evidenc e for the existence of a miscibility gap at lower temperature in the H g1-xCdxTe system. The phase separation occurs primarily in a thin surf ace layer at 140-degrees-C and is reversible after annealing at 530-de grees-C. The compositions of the two compounds at the tie-line at 140- degrees-C are Hg0.22Cd0.78Te and Hg0.63Cd0.37Te.