Tuning the Phase and Optical Properties of Ultrathin SnSx Films

Novel materials suitable for optoelectronics are of great interest due to limited and diminishing energy resources and the movement toward a green earth. We report a simple film growth method to tune the S composition, x from 1 to 2 in semiconductor ultrathin SnSx films on quartz substrates, that is, single phase SnS, single phase SnS2, and mixed phases of both SnS and SnS2 by varying the sulfurization temperature from 150 to 500 °C. Due to the ultrathin nature of the SnSx films, their structural and optical properties are characterized and cross-checked by multiple surface-sensitive techniques. The grazing incidence X-ray diffraction (GIXRD) shows that the single phase SnS forms at 150 °C, single phase SnS2 forms at 350 °C and higher, and mixed phases of SnS and SnS2 form at temperature between. GIXRD shows structures of SnS film and SnS2 film are orthorhombic and 2H hexagonal, respectively. To complement the GIXRD, the reflection high energy electron diffraction pattern analysis shows that both pure pha...