Fast optoelectronic gas sensing with p-type V₂O₅/WS₂/Si heterojunction thin film

Abstract

The efficiency of ultraviolet (UV) illumination in gas adsorption/desorption is remarkable due to its capacity to activate and energize CO₂ molecules, rendering them more reactive and prone to surface interactions. A heterojunction device for room-temperature optoelectronic gas sensing has been fabricated. This was achieved through the deposition of an orthorhombic vanadium pentoxide (V₂O₅) thin film onto a wafer scale 2D p-type tungsten disulfide (WS₂)/silicon (Si). The incorporation of the V₂O₅ layer brings about alterations in WS₂'s electronic properties, resulting in increased energy states for photo-generated carriers and a promising approach to enhance the intensity of exciton and trion peaks. Specifically, the WS₂ film exhibits a carrier concentration of 3.67 × 10¹⁸ cm⁻³, while incorporating the V₂O₅ layer significantly raises this concentration to 1.20 × 10²⁰ cm⁻³. The experiments reveal a rapid response time of 0.4 s and a recovery time of 0.2 s, respectively, demonstrating the swift desorption capability of the device in a CO₂ environment. Remarkably, this device exhibits high optoelectronic performances, boasting a detectivity of 1.22 × 10¹³ Jones and a responsivity of 177.21 A/W. These findings have the potential to advance the development of improved gas-sensing devices, offering heightened sensitivity and selectivity in diverse optoelectronic applications.