RF Sputtered Nb-Doped MoS₂ Thin Film for Effective Detection of NO₂ Gas Molecules: Theoretical and Experimental...

Doping plays a significant role in affecting the physical and chemical properties of two-dimensional (2D) dichalcogenide materials. Controllable doping is one of the major factors in the modification of the electronic and mechanical properties of 2D materials. MoS₂ 2D materials have gained significant attention in gas sensing owing to their high surface-to-volume ratio. However, low response and recovery time hinder their application in practical gas sensors. Herein, we report the enhanced gas response and recovery of Nb-doped MoS₂ gas sensor synthesized through physical vapor deposition (PVD) toward NO₂ at different temperatures. The electronic states of MoS₂ and Nb-doped MOS₂ monolayers grown by PVD were analyzed based on their work functions. Doping with Nb increases the work function of MoS₂ and its electronic properties. The Nb-doped MoS₂ showed an ultrafast response and recovery time of t _rec = 30/85 s toward 5 ppm of NO₂ at their optimal operating temperature (100 °C). The experimental results complement the electron difference density functional theory calculation, showing both physisorption and chemisorption of NO₂ gas molecules on niobium substitution doping in MoS₂.