Band alignment at interfaces of synthetic few-monolayer MoS₂ with SiO₂ from internal photoemission

Electron band alignment at interfaces of SiO₂ with directly synthesized few-monolayer (ML) thin semiconducting MoS₂ films is characterized by using field-dependent internal photoemission of electrons from the valence band of MoS₂ into the oxide conduction band. We found that reducing the grown MoS₂ film thickness from 3 ML to 1 ML leads to 400 meV downshift of the valence band top edge as referenced to the common energy level of the SiO₂ conduction band bottom. Furthermore, comparison of the MoS₂ layers grown by a H-free process (sputtering of Mo in sulfur vapor) to films synthesized by sulfurization of metallic Mo in H₂S indicates a significant (500 meV) electron barrier increase in the last case. This effect is tentatively ascribed to the formation of an interface dipole due to the interaction of hydrogen with the oxide surface.