First-principles study on the adsorption behavior of ZnO and Mn-doped ZnO with CO and NH3 gases

Abstract

The present work investigates the structural, electronic, and magnetic properties of a (3 × 3 × 1) supercell monolayer of Mn doped ZnO (Mn-ZnO), CO adsorbed on ZnO (CO-ZnO), NH₃ adsorbed on ZnO (NH₃-ZnO), and CO & NH₃ adsorbed on Mn-ZnO (CO-Mn-ZnO, & NH₃−Mn-ZnO) structures. Density functional theory (DFT) method with a projected augmented basis set has been used for this study, by employing two different exchange-correlation functionals: GGA-PBE and GGA-PBE+U through the Vienna-Ab-intio Simulation Package (VASP) software. We analyzed the lattice parameters, which reveal that doping Mn into ZnO, and adsorbing NH₃ and CO molecules on both ZnO and Mn-ZnO result in changes to the lattice parameters. Thus, the adsorbed molecules alter the lattice parameters, suggesting that both ZnO and Mn-ZnO have the ability to detect poisonous gases. Moreover, we also studied the band gap energy of considered materials using two functionals, PBE and PBE+U. The obtained band gap energies are closer to the experimental values when applying the PBE+U functional. Lastly, pristine ZnO, as well as CO, and NH₃ adsorbed ZnO (CO-ZnO, & NH₃-ZnO), are found to be non-magnetic, whereas Mn-ZnO, along with CO, and NH₃ adsorbed Mn-ZnO (CO-Mn-ZnO, & NH₃−Mn-ZnO) are found to be magnetic. Based on electronic and magnetic properties, considered materials are suited for sensing devices.