Metallic conduction induced by direct anion site doping in layered SnSe2.

Two dimensional (2D) materials have recently been intensively investigated due to its unique electronic and/or optical properties1,2,3,4,5,6,7. Since the remarkable properties of graphene have initiated the research, other 2D materials with layered structure are also emerged as new counterparts to exhibit striking physical properties under the 2D confined systems1,2,3. Layered dichalcogenides are one of the representative materials drawing great attention from the fact that they can be easily prepared as a form of high quality nanosheet by mechanical and/or chemical exfoliation techniques as graphene did2,4. As a practical engineering method to modulate 2D material properties, doping is an important technique especially for controlling electrical characteristics. Until now, the doping methods for 2D materials have been tried mainly by electrostatic carrier doping introduced by the electrical bias through an dielectric barrier5,6, or insertion of interstitial intercalants between the layer units which are weakly bonded each other by Van der Waals interaction7,8,9. In particular, for the case of layered dichalcogenides, striking carrier transport characteristics can be provoked by effective carrier doping5,6,8,9, but direct substitutional doping has been rarely reported due to the absence of adequate substitutional dopant to the best of our knowledge10. In this study, we report the emergence of metallic conduction in layered dichalcogenide of SnSe2 achieved by direct Se-site doping with Cl atoms. Substitutional Cl dopant on Se-site worked well as a shallow electron donor to increase carrier concentration (ne) up to ~1020 cm−3, and the transition from semiconductor to metallic state was observed when ne exceeded critical limit (~1019 cm−3). Based on the electronic structure calculation, it was clarified that the hybridization between largely spread Sn 5s and Se 4p orbital is the origin of degenerate conduction in Cl-doped SnSe2.