Controlling tin oxysulfide thin film compositions and electronic band structures using atomic layer deposition and vacuum annealing process

Abstract

In this work, we investigated anion-mixed tin oxysulfide thin films in order to search for stable p-type semiconductor materials that can be deposited through atomic layer deposition (ALD). Tin oxysulfide thin films were fabricated through super-cycle repetition of tin sulfide and tin oxide thin films including vacuum annealing process and were analyzed via grazing-incidence X-ray diffraction (GI-XRD), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV–vis.) spectroscopy, and ultraviolet photoelectron spectroscopy (UPS) to investigate the crystallinity, grain size, atomic composition, and electrical and optical properties of the materials according to their ratio of tin sulfide and tin oxide. AES analysis showed that the composition of the thin films changed corresponding to the ratio between sulfur and oxygen. Orthorhombic SnS and rutile SnO2 phase were mixed in the tin oxysulfide thin films. Oxygen from the tin oxides diffused into tin sulfides to produce sulfur vacancies, which changed to p-type characteristics by increasing the oxygen ratio. Through this work, anion-mixed p-type semiconductors with good phase stability can be synthesized and are expected to be applicable to various fields such as p-type material-based transistors, thin film transistors (TFT) and photodetection, biochemical sensors, and photovoltaic energy devices.