Engineering Charge Transfer Doping of MoSe2 Monolayers via Epitaxial Orientation-Dependent Surface Electron Accumulation in high-κ Dielectric Gd2O3 Thin Films

Abstract

Precise control over the doping concentrations of 2D transition metal chalcogenide (TMDC) monolayers (MLs) effectively tunes their physical properties for desired applications. Dielectric substrate surface charge transfer doping (SCTD) which modulates carrier concentration in TMDCs by injecting or extracting carrier charges due to work-function differences, has emerged as a non-destructive and simpler alternative to conventional doping techniques. Understanding the surface properties of epitaxial high-κ dielectrics can provide an excellent platform for the SCTD engineering of TMDC MLs. In this study, we report the SCTD of MoSe2 MLs by epitaxial Gd2O3(110)/Si(100) and Gd2O3(111)/Si(111) layers through temperature-dependent photoluminescence investigations. Comparing the photoluminescence characteristics of MoSe2 MLs on hBN as control samples, we demonstrate a strong enhancement in trion emission for MoSe2 MLs in contact with epitaxial Gd2O3 layers. Enhanced trion emission, resulting from SCTD of MoSe2 MLs by epitaxial Gd2O3 layers, indicates electron doping of approximately 1.18×1010 cm-2 in case of Gd2O3(111)/Si(111), increasing to 3.81×1011 cm-2 for Gd2O3(110)/Si(100). Detailed experimental investigations and theoretical analysis revealed a higher surface concentration of oxygen vacancies for Gd2O3(110) compared to Gd2O3(111) layers, which effectively controls the surface electron accumulation and, thus, SCTD of the adjacent MoSe2 MLs. These results demonstrate a novel approach to reliably tune SCTD of 2D TMDC MLs using epitaxial dielectric substrates.