Molecular Adsorption of NH(3) and NO(2) on Zr and Hf Dichalcogenides (S, Se, Te) Monolayers: A Density Functional Theory Study

Due to their atomic thicknesses and semiconducting properties, two-dimensional transition metal dichalcogenides (TMDCs) are gaining increasing research interest. Among them, Hf- and Zr-based TMDCs demonstrate the unique advantage that their oxides (HfO(2) and ZrO(2)) are excellent dielectric materials. One possible method to precisely tune the material properties of two-dimensional atomically thin nanomaterials is to adsorb molecules on their surfaces as non-bonded dopants. In the present work, the molecular adsorption of NO(2) and NH(3) on the two-dimensional trigonal prismatic (1H) and octahedral (1T) phases of Hf and Zr dichalcogenides (S, Se, Te) is studied using dispersion-corrected periodic density functional theory (DFT) calculations. The adsorption configuration, energy, and charge-transfer properties during molecular adsorption are investigated. In addition, the effects of the molecular dopants (NH(3) and NO(2)) on the electronic structure of the materials are studied. It was observed that the adsorbed NH(3) donates electrons to the conduction band of the Hf (Zr) dichalcogenides, while NO(2) receives electrons from the valance band. Furthermore, the NO(2) dopant affects than NH(3) significantly. The resulting band structure of the molecularly doped Zr and Hf dichalcogenides are modulated by the molecular adsorbates. This study explores, not only the properties of the two-dimensional 1H and 1T phases of Hf and Zr dichalcogenides (S, Se, Te), but also tunes their electronic properties by adsorbing non-bonded dopants.