Interfacial Control of Electron Doping in MoSe₂ Monolayers via Epitaxial Orientation of High-к Dielectric Gd₂O₃

Layered transition metal dichalcogenides (TMDCs) have emerged as a central focus in 2D materials research due to their outstanding properties at the monolayer (ML) level. For practical applications, their integration with suitable dielectric substrates is crucial. The interaction between TMDCs and dielectric substrates can significantly influence excitonic properties through dielectric screening and surface charge transfer doping. Precise control over the doping concentrations of 2D TMDCs through dielectric substrate surface can be effective technique for modulating the charge carrier concentrations in TMDCs for desired applications.

We investigated the impact of the epitaxial orientation of high-k dielectric Gd₂O₃ thin films on the photoluminescence properties of MoSe₂ MLs. The integration with epitaxial Gd₂O₃ layers significantly enhanced trion emission, with a two-fold increase in trion intensity for MoSe₂ on Gd₂O₃(110) compared to Gd₂O₃(111). This enhancement is attributed to surface charge transfer doping of the MoSe₂ MLs, controlled by the epitaxial orientation of the Gd₂O₃ layers. Detailed study revealed a higher concentration of oxygen vacancies on the Gd₂O₃(110) surface compared to the Gd₂O₃(111) surface, due to surface termination-dependent formation energies of the oxygen vacancies. Our work demonstrates that altering the epitaxial dielectric substrate surface orientation can be a simple, non-invasive and efficient tool for engineering the excitonic properties of TMDCs