Electronic coupling in the F4-TCNQ/single-layer GaSe heterostructure

Abstract

Hybrid heterostructures, made of organic molecules adsorbed on two-dimensional metal monochalcogenide,generally unveil interfacial effects that improve the electronic properties of the single constitutive layers. Here,we investigate the interfacial electronic characteristics of the F4-TCNQ/single-layer GaSe heterostructure. Asharp F4-TCNQ/GaSe interface has been obtained and characterized by x-ray photoemission spectroscopy. Wedemonstrate that a high electron transfer from 1TL GaSe into the adsorbed F4-TCNQ molecules takes place,thereby yielding a reduction in the excess negative charge density of GaSe. Additionally, the direct band-structuredetermination of the heterostructure has been carried out using angle-resolved photoemission spectroscopy,shedding light on essential features such as doping and band offset at the interface. Our results indicate thatthe buried 1TL GaSe below the F4-TCNQ layer exhibits a robust inversion of the valence dispersion at thepoint, forming a Mexican-hat-shaped dispersion with 120±10 meV of depth. Our experiments also revealthat F4-TCNQ can significantly tune the electronic properties of 1TL GaSe by shifting the band offset of about0.16 eV toward lower binding energies with respect to the Fermi level, which is a key feature for envisioning itsapplications in nanoelectronics.