Crystallographic properties and optical energy gap values for (CuIn)x(AgIn)yCd2zTe2 alloys

Abstract
Polycrystalline samples of (CuIn)x(AgIn)yCd2zTe2 were prepared by a melt and anneal technique. Guinier x‐ray powder photographs were used to determine equilibrium conditions and lattice parameter values. Two single‐phase fields, with zinc‐blende and chalcopyrite structures, are found to exist in the diagram. Comparison of the experimental results with the expressions proposed by Jaffe and Zunger has been made. It was found that these equations, used with Phillips radii, give good agreement for parameter a for Cu‐rich samples but poorer agreement elsewhere and also for c and c/a. Optical absorption measurements were carried out on most of the samples to determine values of the optical energy gap E0 at room temperature. These values of E0 are found to show a nonlinear variation with z. This variation is discussed in terms of the effects of pd hybridization on the valence band and the change in crystal structure.

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