Large-area MoS2-MoOx heterojunction thin-film photodetectors with wide spectral range and enhanced photoresponse

We report the enhanced photoresponse in MoS2-MoOx heterojunction thin film structures on SiO2/Si substrates to demonstrate the feasibility of using them as highly responsive photodetectors with a wide spectral range from visible to near-ultraviolet light. Vertically stacked MoS2-MoOx heterojunction structures were obtained through two-step chemical vapor deposition composed of MoOx thin film deposition and subsequent sulfurization of the topmost region of as-deposited MoOx into MoS2. The formation of heterojunction structures was revealed by transmission electron microscopy and x-ray photoelectron spectroscopy analysis. Under an incident light of 405 nm and 638 nm in wavelength, our MoS2-MoOx heterojunction thin film structures exhibited significantly higher absorbance, photoresponsivity, and specific detectivity than MoOx thin films. Moreover, a highly uniform photoresponse was obtained throughout heterojunction thin film structures. These results demonstrate that MoS2-MoOx heterojunction thin film structures can be a potentially promising material system scalable into large-area photodiode arrays to build active-matrix high-energy-selective photodetectors.