Single- and few-layer 2H-SnS2 and 4H-SnS2 nanosheets for high-performance photodetection

The properties of two-dimensional (2D) materials are highly dependent on their phase and thickness. Various phases exist in tin disulfide (SnS 2 ), resulting in promising electronic and optical properties . Hence, accurately identifying the phase and thickness of SnS 2 nanosheets is prior to their optoelectronic applications . Herein, layered 2H-SnS 2 and 4H-SnS 2 crystals were grown by chemical vapor transportation and the crystalline phase of SnS 2 was characterized by X-ray diffraction, ultralow frequency (ULF) Raman spectroscopy and high-resolution transmission electron microscope . As-grown crystals were mechanically exfoliated to single- and few-layer nanosheets , which were investigated by optical microscopy, atomic force microscopy and ULF Raman spectroscopy . Although the 2H-SnS 2 and 4H-SnS 2 nanosheets have similar optical contrast on SiO 2 /Si substrates, their ULF Raman spectra obviously show different shear and breathing modes, which are highly dependent on their phases and thicknesses. Interestingly, the SnS 2 nanosheets have shown phase-dependent electrical properties. The 4H-SnS 2 nanosheet shows a current on/off ratio of 2.58 × 10 5 and excellent photosensitivity, which are much higher than those of the 2H-SnS 2 nanosheet. Our work not only offers an accurate method for identifying single- and few-layer SnS 2 nanosheets with different phases, but also paves the way for the application of SnS 2 nanosheets in high-performance optoelectronic devices .