Cation-Regulated Transformation for Continuous Two-Dimensional Tin Monosulfide

The synthesis of a continuous and high-quality large-area layer is a key research area in the field of two-dimensional (2D) metal chalcogenides. To date, several techniques, including chemical vapor deposition and sulfurization/selenization, have been proposed for the synthesis of 2D metal chalcogenides. These techniques are based on the substitutional reaction of anions, that is, replacement of oxygen with chalcogen elements. This study uses a new approach based on cation-regulated transformation. An SnS2 layer, a parent material, is grown by atomic layer deposition, followed by reaction with bis(1-dimethlamino-2-methyl-2-propoxy)tin(II) at a temperature of 270 degrees C to form SnS. The reaction occurs predominantly along grain boundaries. The transformation self-terminates once the pregrown SnS2 is completely consumed. The devices utilizing the transformed layers, such as gas sensors and thin-film transistors, exhibit a p-type behavior, supporting full transformation of n-type SnS2 into p-type SnS. Consequently, complete transformation into a continuous and single-phase SnS layer is demonstrated by the cation-regulated transformation approach. This approach provides possibilities to expand approaches to the synthesis of more diverse 2D metal chalcogenides and the modulation of their properties.