Impact of N-Doping on MoSe2 Monolayer for PH3, C2N2, and HN3 Gas Sensing: A DFT Study

In this research, the different characteristics of MoSe2 and N-doped MoSe2 monolayers were studied using density functional theory calculations. The negative cohesive energy (-5.216 eV for MoSe2 and -5.333 eV for N-MoSe2) verified their energetical stability. The variation of structural, electronic, and optical properties of MoSe2 and N-MoSe2 via adsorption of PH3, C2N2, and HN3 gases are studied. The N-doping results in a stronger adsorbent-gas interaction, resulting in maximum adsorption energy of -0.036, -0.033, and -0.198 eV for the selected gases. The MoSe2 and N-MoSe2 monolayers showed a direct band gap of 1.48 eV and 1.09 eV, respectively. However, upon interaction with the gases, a notable shift in the band gap of both adsorbents is observed. N-MoSe2 showed semiconductor-to-conductor transition via C2N2 and HN3 adsorption. The sensitivity of MoSe2 for the selected gases has improved remarkably via N-doping. Also, HN3 gas can be easily detected by the N-MoSe2 monolayer due to the greater changes in work function (0.45 eV). The absorption coefficient of both adsorbents is over 10(5) cm(-1) order in the UV region, which suffers a mild peak shifting due to gas adsorption. This study suggests that N-MoSe2 can be a potential candidate for selected gas sensing.