Ab initio study of adsorption behaviors of molecular adsorbates on the surface and at the edge of MoS2

Two dimensional (2D) semiconducting materials such as MoS₂ have been actively investigated for their applications in nanodevices and gas sensors (or detectors). In this connection, we have investigated atomic and electronic structures of specific adsorbates on the surface of MoS₂ and the edge of MoS₂ armchair nanoribbons (ANRs) using density functional theory (DFT) calculations. Our calculations reveal that molecular adsorbates are well adsorbed at the edge of MoS₂ than on the surface of MoS₂. Despite the weak van der Waals (vdW) interaction between molecular adsorbates and MoS₂ surface, paramagnetic molecules such as NO and NO₂ induce the reduced band gap in MoS₂ by making the states within the bandgap. On the other hand, adsorbed CO, NO, NO₂, and O₂ at the edge of MoS₂ ANRs have much influence on the band structures of MoS₂ ANRs via dissociation into their constituent atoms, while adsorbed CO₂, NH₃, H₂, and N₂ at the edge of MoS₂ ANRs do not much change the band structure of MoS₂ ANRs due to no dissociation. Further, we identify that dissociated molecules rearrange the charge densities of MoS₂ ANRs by making the states within the bandgap.