Tin monosulfide (SnS) epitaxial films grown by RF magnetron sputtering and sulfurization on MgO(100) substrates

The crystallographic and electrical properties of tin monosulfide (SnS) epitaxial thin films grown by RF magnetron sputtering and sulfurization were investigated. The SnS(040)-oriented films were grown on a MgO(100) substrate. Two types of four-fold rotational symmetrical in-plane orientations, offset by 45° from each other, were observed using X-ray diffraction. The rotational symmetry was also observed using cross-sectional transmission electron microscopy. The electrical properties of the SnS films were controlled by varying the sulfurization temperature, and the carrier transport of all the SnS epitaxial films was mainly limited by grain boundary scattering. The activation energies of the carrier concentration before and after sulfurization of the films were estimated to be approximately 0.26 ± 0.02 eV and 0.20 ± 0.01 eV, respectively, based on temperature-dependent Hall measurements. These values mainly correspond to the acceptor level energy of Sn vacancy with a high/low potential barrier height around the grain boundary.