AQUEOUS-SOLUTION EPITAXY OF CDS LAYERS ON CUINSE2

Epitaxial CdS thin films have been deposited from an aqueous ammonia s olution containing cadmium ions and thiourea as precursors on single c rystalline CuInSe2 films prepared by MBE on Si(1 1 1) and GaAs(1 0 0) substrates. The structure and quality of the films were investigated b y RHEED, glancing angle XRD and HRTEM in cross-section. The films are cubic on (1 0 0) substrates, and mixed cubic and hexagonal on (1 1 1) substrates due to the presence of stacking faults parallel to the subs trate. The growth is under surface kinetic control with an activation energy of 85 kJ mol(-1). Epitaxy improves with increasing temperature and an epitaxial transition temperature at approx. 60 degrees C is dem onstrated in the selected experimental conditions. The epitaxy is very sensitive to the preparation of the surface. Beneficial effects of in situ or ex situ chemical etching are found. Similarities between aque ous solution and vapor-phase chemical depositions are pointed out. (C) 1998 Published by Elsevier Science B.V. All rights reserved.