Material-selective doping of 2D TMDC through AlxOy encapsulation

For the integration of 2D Transition Metal Di-Chalcogenides (TMDC) with high performance electronic systems, one of the greatest challenges is the realization of doping and comprehension of its mechanisms. Low temperature atomic layer deposition of aluminum oxide is found to n-dope MoS2 and ReS2, but not WS2. Based on electrical, optical, and chemical analysis, we propose and validate a hypothesis to explain the doping mechanism. Doping is ascribed to donor states in the bandgap of AlxOy, which donate electrons or not, based on the alignment of the electronic bands of the 2D TMDC. Through systematic experimental characterization, carbon incorporation is identified as the likely cause of such states. By modulating the carbon concentration in the capping oxide, the doping can be controlled. This is the first study to correlate 2D TMDC doping to the carbon incorporation on dielectric encapsulation layers. We highlight the possibility to engineer dopant layers in order to control the material selectivity and ...