Covalent nitrogen doping in molecular beam epitaxy-grown and bulk WSe2

Ava Khosravi,Ruoyu Yue,Jiyoung Kim,Christopher R. Cormier,Rafik Addou,Robert M. Wallace,Christopher L. Hinkle,Christopher M. Smyth

doi:10.1063/1.5002132

Abstract

Covalent p-type doping of WSe2 thin films grown by molecular beam epitaxy and WSe2 exfoliated from bulk crystals is achieved via remote nitrogen plasma exposure. X-ray photoelectron and Raman spectroscopies indicate covalently bonded nitrogen in the WSe2 lattice as well as tunable nitrogen concentration with N2 plasma exposure time. Furthermore, nitrogen incorporation induces compressive strain on the WSe2 lattice after N2 plasma exposure. Finally, atomic force microscopy and scanning tunneling microscopy reveal that N2 plasma treatment needs to be carefully tuned to avoid any unwanted strain or surface damage.

Highlights

Transition metal dichalcogenides (TMDs), a family of two-dimensional (2D) materials with layered structure, have gained much attention recently due to their unique material properties like atomic-scale thickness, sizeable bandgap, and potential applications in various electronic and optoelectronic devices such as tunneling field-effect transistors (FETs), p-n diodes, and photovoltaics.[1,2,3,4]
A more manufacturable approach, using a remote N2 plasma, has been employed previously to introduce nitrogen into the graphene lattice.[14,15]. This remote N2 plasma method was reported as a successful method for controllable doping of exfoliated MoS2.16 In this work, we extend and compare the effect of similar N2 plasma treatment on bulk WSe2 and on a few monolayers of WSe2 grown by molecular beam epitaxy (MBE)
Samples were heated to 300 ◦C under ultra-high vacuum (UHV) and held at this temperature for 2 h to remove physisorbed species induced by air exposure following exfoliation

Summary

Introduction

Transition metal dichalcogenides (TMDs), a family of two-dimensional (2D) materials with layered structure, have gained much attention recently due to their unique material properties like atomic-scale thickness, sizeable bandgap, and potential applications in various electronic and optoelectronic devices such as tunneling field-effect transistors (FETs), p-n diodes, and photovoltaics.[1,2,3,4].

Results

Conclusion