CuInSe2 phase formation during Cu2Se/In2Se3 interdiffusion reaction

Diffusion couples based upon Cu2Se/In2Se3 pairings have been examined in order to identify the kinetics of intermediate phase development and the associated phase equilibria. For the diffusion couples annealed at 550 degrees C for 1.5 h, all phases included in the Cu2Se-In2Se3 pseudobinary phase diagram section developed including the CuInSe2 (CIS) phase. Also, the In6Se7 phase formed for annealing times in excess of 1.5 h at 550 degrees C, indicating a modification of the diffusion pathway outside the pseudobinary phase diagram section. The growth of the CIS phase formed by reactive diffusion follows parabolic kinetics (x(2)=kt) with the k value of 3.3x10(-8) cm(2)/s. CIS phase precipitates with a dendritic morphology are also produced within the Cu2Se side of the diffusion couple far from the initial interface, indicating that In is the fast component during interdiffusion. Based upon electron diffraction analysis and simulation of electron diffraction patterns, the dendritic shaped CIS precipitate structure was uniquely determined to be the metastable zinc blende type rather than the stable chalcopyrite-type structure. The structure and orientation relationship between the metastable CIS phase and the Cu2Se matrix satisfy the conditions established for the development of a solid state dendritic morphology. (C) 2000 American Institute of Physics. [S0021-8979(00)06508-7].