Spectroscopic Characterization of Colloidally Synthesized, Anisotropic 2D SnS

Solution routes afford scalable means of manufacturing size-, shape-, and composition-controlled nanoscale electronic materials. We have developed solution routes to monodisperse 2D semiconductor SnS nanostructures, an easily processable and cost-efficient alternative to exfoliation and gas-phase deposition techniques. These colloidal chemistries afford two distinct SnS morphologies: nanoribbons and square nanosheets. The uniformity and morphology of the nanocrystals were verified using TEM, SEM, AFM, and optical microscopy. A spectroscopic investigation of the inherent structural and electronic properties of nanocrystals showed the α-SnS polymorph adopts a layered orthorhombic crystal structure, isostructural with black phosphorus. These 2D crystals are anisotropic, with in-plane atoms adopting the armchair configuration along one axis and zigzag in the orthogonal direction. Detailed polarization-, wavelength- and temperature-dependent Raman spectroscopy provide key insight into the crystallographic details and low-frequency phonon behavior. Back-gated devices fabricated from individual crystals reveal electronic transport information and four-point probe methods show the anisotropic conductivity resulting from a black phosphorus-like bonding arrangement found in 2D SnS.