Interfacial Oxidation Unlocks Degenerate n‑Doping in Monolayer MoS₂

Combining photoelectron spectroscopy, diffraction, and microscopy, we demonstrate that placing single-layer MoS₂ in contact with a pristine Bi layer results only in weak <i>n</i>-doping and no detectable conduction-band occupation, whereas oxidation of the Bi layer produces a pronounced occupation of the MoS₂ conduction band with an electron density on the order of 10¹³ cm^–2.

We attribute this strong <i>n</i>-type charge transfer to the formation of an ultrathin <i>β</i>-Bi₂O₃-like layer with an unusually low effective work function, consistent with our measurements and calculations for an ideal Bi-terminated <i>β</i>-Bi₂O₃(201) surface. These results establish interfacial oxidation as a means to engineer strong <i>n</i>-type charge transfer at transition metal dichalcogenide interfaces and motivate future transport studies of oxide-mediated contact architectures.