Chemical epitaxy of π-phase cubic tin monosulphide

Abstract

Thin films of tin monosulfide were chemically deposited on GaAs substrates and on GaAs with intermediate PbS layers. GaAs surface treatments with alkaline solutions containing Pb²⁺ were shown to facilitate the formation of π-SnS, a new cubic polymorph in the tin monosulfide system. Compactness and phase purity of the films were further improved when depositing onto a chemically deposited PbS intermediate layer, resulting in epitaxial orientation relations between the layers. Deposition onto GaAs(111) resulted in (111)[01]_PbS‖(111)[01]_π-SnS, while deposition onto GaAs(100) resulted in (110)[001]_PbS‖(110)[001]_π-SnS. Polarized Raman measurements demonstrated inherent anisotropy, as expected for epitaxial films.