Substitutional Fluorine Doping of Large-Area Molybdenum Disulfide Monolayer Films for Flexible Inverter Device Arrays

Reliable and controllable doping of transition metal dichalcogenides (TMDCs) is a mandatory requirement for practical large-scale electronic applications. However, most of the literature on the doping methodologies of TMDCs has focused on n-type doping and multilayer TMDC rather than a monolayer one enabling large-scale growth. Herein, we report substitutional fluorine doping of a chemical vapor deposition (CVD)-grown molybdenum disulfide (MoS₂) monolayer film using a delicate SF₆ plasma treatment. Our SF₆-treated MoS₂ monolayer shows a p-type doping effect with fluorine substitution. The doping concentration is controlled by the plasma treatment time (2–4.9 atom %) while maintaining the structural integrity of the MoS₂ monolayer. Such reliable and tunable substitutional doping is attributed to preventing direct ion bombardment to the MoS₂ monolayer by our gentle plasma treatment system. Finally, we fabricated MoS₂ homojunction flexible inverter device arrays based on the pristine and SF₆-treated MoS₂ monolayer. A clear switching behavior is observed, and the voltage gain is approximately 8 at an applied V_DD of 2 V, which is comparable to that of CVD-grown MoS₂-based inverter devices reported previously. Obtained voltage gain is also stable even after 500 bending cycles at an applied strain of 0.5%.