Effects of plasma conditions on sulfurization of MoO3 thin films and surface evolution for formation of MoS2 at low temperatures

Recently, two-dimensional (2D) MoS2 with the superior properties has been extensively investigated as a nextgeneration semiconductor channel material to electronic and optoelectronic devices. In order to apply MoS2 thin films to the industrial application, it is important not only to secure excellent properties but also to develop a suitable process for their large area synthesis. Among the various kinds of synthesis methods, the plasma sulfurization of transition metals or oxides has been considered a promising way to form 2D transition metal sulfides at low temperatures. However, there have been an insufficient number of systematic studies of surface phenomena during the plasma sulfurization. Therefore, this study examined the effects of the plasma conditions on the sulfurization process to form uniform MoS2 thin films. It was discovered that the introduction of hydrogen to the H2S gas during the plasma period and the thickness of the initially formed MoO3 thin films had important effects on the obtaining of continuous MoS2 thin films. Furthermore, a model of the surface evolution occurring during the plasma sulfurization process was proposed based on the observations. The results of this work could inspire other researchers and assist in the study of the sulfurization of various other oxides films.