Analysis of p-Type Doping in Graphene Induced by Monolayer-Oxidized TMDs

Doping is one of the most difficult technological challenges for realizing reliable two-dimensional (2D) material-based semiconductor devices, arising from their ultrathinness. Here, we systematically investigate the impact of different types of nonstoichiometric solid MO x (M are W or Mo) dopants obtained by oxidizing transition metal dichalcogenides (TMDs: WSe 2 or MoS 2 ) formed on graphene FETs, which results in p -type doping along with disorders. From the results obtained in this study, we were able to suggest an analytical technique to optimize the optimal UV-ozone (UVO) treatment to achieve high p -type doping concentration in graphene FETs (∼2.5 × 10 13 cm –2 in this study) without generating defects, mainly by analyzing the time dependency of D and D ′ peaks measured by Raman spectroscopy. Furthermore, an analysis of the structure of graphene sheets using TEM indicates that WO x plays a better protective role in graphene, compared to MoO x, suggesting that WO x is more effective for preventing the degradation of graphene during UVO treatment. To enhance the practical application aspect of our work, we have fabricated a graphene photodetector by selectively doping the graphene through oxidized TMDs, creating a p – n junction, which resulted in improved photoresponsivity compared to the intrinsic graphene device. Our results offer a practical guideline for the utilization of surface charge transfer doping of graphene toward CMOS applications.