Growth and microstructural characterization of SnSe-SnSe2 composite

As the Sn-Se eutectic solidification produces a lamellar structure, formed by SnSe and SnSe2 compound, which are p and n semiconducting type, respectively, the SnSe-SnSe2 in situ composite is a promising material to be used in photovoltaic device manufacturing. In this work, the Sn-Se alloys corresponding to the eutectic composition as well as to SnSe and SnSe2 composition were processed by direction solidification at several solidification rates in a vertical Bridgman-Stockbarger crystal growth unit. The aim of the experiments was to evaluate the eutectic microstructure behavior as a function of directional solidification parameters. The obtained microstructures were analyzed by using X-ray diffraction and scanning electron and optical microscopies. The results obtained show that a very regular and aligned structure formed by the SnSe and SnSe2 solid phase can be achieved. It was found that the presence of imperfections in the eutectic microstructure depends on the growth rate, and mainly, on the alloy homogenization process. (C) 1999 Kluwer Academic Publishers.