Sulfur vacancy defect control: Favorable impact on the photodetection performance of MoS2/WSe2 van der Waals heterojunction

Two-dimensional (2D) transition metal chalcogenides (TMDs) exhibit enormous potential in the field of optoelectronic devices. Chemical vapor deposition (CVD) is considered a promising method for the preparation of high-quality TMDs. However, through the CVD method, defects are easily introduced into TMDs. In order to fundamentally suppress the generation of defects, we for the first time proposed the time stepping method. This method regulates the concentration of S steam by turning the heating time of S source. We discovered suitable concentration of S steam can promote S-Mo covalent bonding, inhibit the generation of sulfur vacancy (VS) defects, and facilitate the acquisition of high crystalline quality MoS2. The optimized MoS2 has been used to construct a MoS2/WSe2 heterojunction photodetector with high responsivity (41.15 A & sdot;W-1) and fast response speed (102 mu s). This work provides valuable insights into the regulation of VS defects density, and extends its application field in high-performance optoelectronic devices.