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, respecti vely, the SnSe-SnSe2 in situ composite is a promising material to be used i n photovoltaic device manufacturing. In this work, the Sn-Se alloys corresp onding 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 exp eriments was to evaluate the eutectic microstructure behavior as a function of directional solidification parameters. The obtained microstructures wer e analyzed by using X-ray diffraction and scanning electron and optical mic roscopies. The results obtained show that a very regular and aligned struct ure formed by the SnSe and SnSe2 solid phase can be achieved. It was found that the presence of imperfections in the eutectic microstructure depends o n the growth rate, and mainly, on the alloy homogenization process. (C) 199 9 Kluwer Academic Publishers.