Efficient n- and p-Type Molecular Dopings in Large-Scale Monolayer Dichalcogenides for High-Performance Field-Effect Transistors

Abstract

Doping engineering has been actively investigated for two-dimensional (2D) transition metal dichalcogenides (TMDs) to enhance their electrical behavior, particularly for use in field-effect transistors (FETs). Here, we propose unprecedented redox-active n-type and p-type dopants, naphthalene and WCl₆, respectively, for large-scale monolayer MoS₂ films synthesized via low-pressure chemical vapor deposition using a Na₂S promoter. These molecular dopants were selected based on their high redox potentials versus the reference ferrocene, which facilitated the ionization of the dopants via charge transfer. Along with the suppression effect of sulfur vacancies in the monolayer, the electronic transport behavior exhibits an ultrahigh electron mobility of 331.7 cm² V^–1 s^–1 for the n-doped MoS₂ FET and an excellent hole mobility of 31.8 cm² V^–1 s^–1 with a high on/off ratio of ∼10⁷ for the p-type FET, all of which are record-setting values among those reported for large-scale monolayer MoS₂ and chemically doped TMD-based FETs. The modulation in the dopant concentration and its correlation with the transistor performance are mainly demonstrated, along with the adjusted band structures as the potential origin of the exceptional outcomes. The extended exploration of multiple FET devices within a single large-scale monolayer film demonstrated uniform electrical characteristics.