Abstract
The emergence of metallic conduction in layered dichalcogenide semiconductor materials by chemical doping is one of key issues for two-dimensional (2D) materials engineering. At present, doping methods for layered dichalcogenide materials have been limited to an ion intercalation between layer units or electrostatic carrier doping by electrical bias owing to the absence of appropriate substitutional dopant for increasing the carrier concentration. Here, we report the occurrence of metallic conduction in the layered dichalcogenide of SnSe2 by the direct Se-site doping with Cl as a shallow electron donor. The total carrier concentration up to ~1020 cm−3 is achieved by Cl substitutional doping, resulting in the improved conductivity value of ~170 S·cm−1 from ~1.7 S·cm−1 for non-doped SnSe2. When the carrier concentration exceeds ~1019 cm−3, the conduction mechanism is changed from hopping to degenerate conduction, exhibiting metal-insulator transition behavior. Detailed band structure calculation reveals that the hybridized s-p orbital from Sn 5s and Se 4p states is responsible for the degenerate metallic conduction in electron-doped SnSe2.
Highlights
Characteristic Cl 2p core level peak at 199.05 eV was observed with sample H while sample A did not show any Cl related one
From the fact that the measured core level corresponds well with Cl– state which is almost identical to the Cl 2p position in the form of CdCl213, it indicates that the Cl dopant exists as Cl– state which could serve well as an electron donor if it substitutes on Se2− site
With sample H, we could observe the downshift and the peak broadening occurred for A1g mode compared to those from sample A14
Summary
From the fact that the measured core level corresponds well with Cl– state which is almost identical to the Cl 2p position in the form of CdCl213, it indicates that the Cl dopant exists as Cl– state which could serve well as an electron donor if it substitutes on Se2− site. It strongly evidences that Cl dopant well substitutes on Se-site as decreasing the force constant in SnSe2 as reported in other substitutionally doped materials[15,16,17].
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