Covalent Nitrogen Doping and Compressive Strain in MoS2 by Remote N2 Plasma Exposure

TL;DR

This study demonstrates a novel nitrogen doping method in MoS2 using remote plasma, which induces covalent bonding and compressive strain, enhancing its electronic properties for device applications.

Contribution

It introduces a remote N2 plasma technique for covalent nitrogen doping in MoS2 and reveals strain effects caused by substitutional doping.

Findings

Nitrogen covalently bonds with MoS2 surface.

Nitrogen doping induces p-type conductivity.

Doping causes measurable compressive strain.

Abstract

Controllable doping of two-dimensional materials is highly desired for ideal device performance in both hetero- and p-n homo-junctions. Herein, we propose an effective strategy for doping of MoS2 with nitrogen through a remote N2 plasma surface treatment. By monitoring the surface chemistry of MoS2 upon N2 plasma exposure using in-situ X-ray photoelectron spectroscopy, we identified the presence of covalently bonded nitrogen in MoS2, where substitution of the chalcogen sulfur by nitrogen is determined as the doping mechanism. Furthermore, the electrical characterization demonstrates that p-type doping of MoS2 is achieved by nitrogen doping, in agreement with theoretical predictions. Notably, we found that the presence of nitrogen can induce compressive strain in the MoS2 structure, which represents the first evidence of strain induced by substitutional doping in a transition metal dichalcogenide material. Finally, our first principle calculations support the experimental demonstration of such strain, and a correlation between nitrogen doping concentration and compressive strain in MoS2 is elucidated.