Chemically Tuned p- and n-Type WSe₂ Monolayers with High Carrier Mobility for Advanced Electronics

Monolayers of transition metal dichalcogenides (TMDCs) have attracted a great interest for post-silicon electronics and photonics due to their high carrier mobility, tunable bandgap, and atom-thick 2D structure. With the analogy to conventional silicon electronics, establishing a method to convert TMDC to p- and n-type semiconductors is essential for various device applications, such as complementary metal-oxide-semiconductor (CMOS) circuits and photovoltaics. Here, a successful control of the electrical polarity of monolayer WSe₂ is demonstrated by chemical doping. Two different molecules, 4-nitrobenzenediazonium tetrafluoroborate and diethylenetriamine, are utilized to convert ambipolar WSe₂ field-effect transistors (FETs) to p- and n-type, respectively. Moreover, the chemically doped WSe₂ show increased effective carrier mobilities of 82 and 25 cm² V^-1 s^-1 for holes and electrons, respectively, which are much higher than those of the pristine WSe₂ . The doping effects are studied by photoluminescence, Raman, X-ray photoelectron spectroscopy, and density functional theory. Chemically tuned WSe₂ FETs are integrated into CMOS inverters, exhibiting extremely low power consumption (≈0.17 nW). Furthermore, a p-n junction within single WSe₂ grain is realized via spatially controlled chemical doping. The chemical doping method for controlling the transport properties of WSe₂ will contribute to the development of TMDC-based advanced electronics.