Effect of hydrogen and oxygen plasma on the photoelectronic current and photo-response time of SnS2 flakes

Abstract

The photoelectronic properties of SnS2 flakes have been widely studied due to the abundance and environmentally friendly qualities of this material. However, the defects and residual molecules adsorbed on the SnS2 surface can have a negative influence on the photoelectronic current and photo-response time. In this paper we examine the effects of these two factors on the photoelectronic currents of SnS2 flakes. Defects on a single crystal SnS2 surface are fabricated using hydrogen and oxygen plasma and are characterized by atomic force microscopy, confocal micro-Raman spectroscopy and photoluminescence spectroscopy. Doping by oxygen plasma can be demonstrated by x-ray photoelectron spectroscopy. Both the photoelectronic current and the switching speed (on and off times) are reduced after hydrogen plasma treatment. However, oxygen plasma has two effects on SnS2 thin film transistors. First, oxygen plasma can remove the residual molecules within a short irradiation time. In this case, the photoelectronic current of SnS2 treated with oxygen plasma is enhanced several times. Second, with a longer treatment time oxygen plasma induces many defects and doping on the SnS2 flake surface, as reflected in the reduced photoelectronic current and switching speed. Results of this work have significant practical applications for photoelectronic detection with SnS2 flakes.