CLOSE-SPACED VAPOR TRANSPORT OF CUINSE2, CUGASE2 AND CU(GA, IN)SE2

We have grown CuInSe2, CuGaSe2 and Cu(Ga, In)Se2 thin films by a simple method using the close-spaced vapour transport technique. The deposits were made at temperatures lower than 620-degrees-C, in glass tubes sealed under vacuum after the introduction of solid iodine. Glass or molybdenum substrates may be used. The thin films obtained at temperatures above 550-degrees-C have a composition close to the stoichiometric composition. A thermodynamic study of the transport is carried out, and the chemical reactions are established. We show that the transport is mainly governed by diffusion, except for low iodine concentrations (less than 0.1 mg cm-3), for which limitations due to reaction and surface kinetics appear, and high iodine concentrations (above 0.5 mg cm-3), for which surface mechanisms at the substrate limit the deposition.