Layer-by-Layer Oxidation Induced Electronic Properties in Transition-Metal Dichalcogenides

Recent progress in transition-metal dichalcogenides has opened up new possibilities for atomically thin nanomaterial based electronic device applications. Here we investigate atomic-scale self-assembled heterojunction modulated by layer-by-layer controlled oxidation in monolayer and few-layer dichalcogenide systems and their electronic properties within a first-principles framework. Pristine dichalcogenide systems exhibit semiconducting behavior. We observe reduction of the band gap for partial oxidation of the top layer. However, complete oxidation of the top layer makes the system metallic, owing to the charge transfer from the pristine to the oxidized layer, as observed in recent experiments. When the bottom layer gets partially oxidized with fully oxidized top layers, the system shows unprecedented semimetallic behavior. The appearance of valence band maximum and conduction band minimum at different k-points can introduce valley polarization. Therefore, our study shows controlled oxidation induced varying electronic properties in dichalcogenide based heterojunctions that can be exploited for advanced electronic, optoelectronic, and valleytronic device applications