Synthesis of Submillimeter SnSexS2-x (0<x<1) Two-dimensional Alloy and Photoinduced Reversible Transformation between Schottky and Ohmic Contact Behaviors in Devices
Abstract
Large-scale controllable synthesis of high-quality alloyed semiconductors with precise component and electronic modulation are of great importance for their applications in electronics and optoelectronics. Here, we demonstrate the direct synthesis of two-dimensional SnSexS2-x alloy via chemical vapor deposition (CVD) technique. Size of single-crystal flakes could reach up to 750 μm, ten times larger than previously reported CVD grown SnS2 and SnSe2. Morphology of the atmospheric pressure CVD grown SnSexS2-x flakes revealed an evolution from semi-hexagon to semi-circle as content of Se atom increased, while the low-pressure CVD alloyed flakes kept a constant shape of semi-hexagon. UV-visible spectroscopy and PL measurement revealed adjustability of band in the alloy flakes, where the higher Se atom content caused a narrower band gap. The SnSexS2-x devices performed high Ilight/Idark ratio under switching between light and dark, whose rise and fall time were just 225.9 μs and 646.2 μs, respectively. More importantly, the devices showed a Schottky-contact performance in dark condition, while it turned to be Ohmic performance under illumination, leading to a tunable Ilight/Idark ratio controlled by bias voltage between drain and source. This work can help the large-area growth technique and unique electrical properties improvement of two-dimensional alloys be closer to practical applications.
