Surface charge transfer doping of monolayer molybdenum disulfide by black phosphorus quantum dots

Monolayer molybdenum disulfide (MoS₂), consisting of covalently bonded S-Mo-S sandwiched layers, has high carrier mobility and a direct bandgap of 1.8 eV, offering properties for electronic and optoelectronic devices with high performance. Usually, it is essential to modulate the carrier concentrations and conductivities of monolayer MoS₂ for practical applications. In this paper, black phosphorus (BP) quantum dots (QDs) were synthesized by a liquid exfoliation method successfully, and have a diameter of ∼5 nm as confirmed with a transmission electron microscope (TEM). BP QDs were utilized to decorate monolayer MoS₂ grown by chemical vapor deposition (CVD). The Raman and PL spectra of the BP QD/MoS₂ hybrid structure clearly indicate that BP QDs are an effective n-type doping scheme for monolayer MoS₂. Back-gated monolayer MoS₂ transistors were fabricated and show an improved source-drain current after BP QD modifications. A high electron concentration of ∼5.39 × 10¹² cm^-2 in monolayer MoS₂ was achieved, which is beneficial for designing FETs and photodetector devices with novel functions.