High contact resistance remains a central obstacle to the integration of two-dimensional (2D) semiconductors in electronic devices. Recent advances have demonstrated that contact performance can be dramatically improved through interface engineering, including the use of group-V semimetals and charge-transfer contacts based on strong interfacial doping. Here, we show that controlled interfacial oxidation provides an effective route to convert a semimetal contact into a charge-transfer contact that degenerately n-dopes single layer MoS2. Using a combination of angle-resolved photoemission spectroscopy, X-ray photoelectron diffraction, low-energy electron diffraction and scanning tunnelling spectroscopy, we demonstrate that putting single layer MoS2 in contact with a pristine Bi layer merely results in weak doping, whereas oxidation of the Bi layer leads to a pronounced occupation of the MoS2 conduction band with an electron density on the order of 1013~cm−2. The cause of this strong electron doping is the fact that an ultrathin β-Bi2O3 layer forms below the MoS2 and that this has a particularly low work function, thereby acting as an efficient electron donor to MoS2. Interfacial oxidation thus emerges as a powerful design knob for engineering charge-transfer contacts to 2D semiconductors.
@article{arxiv.2602.24057,
title = {Interfacial Oxidation Enables Charge-Transfer Contacts and Degenerate n-Doping in Monolayer MoS$_2$},
author = {Marco Bianchi and Daniel Lizzit and Alberto Turoldo and Ezequiel Tosi and Paolo Lacovig and Monika Schied and Davide Curcio and Charlotte E. Sanders and Silvano Lizzit and Philip Hofmann},
journal= {arXiv preprint arXiv:2602.24057},
year = {2026}
}