High-quality monolayer superconductor NbSe2 grown by chemical vapour deposition

Hong Wang,Junhao Lin,Jian Cui,F.c Ma ,Li Lü ,Weibo Gao,Qingsheng Zeng,Haibing He ,Xuewen Wang,Kazu Suenaga,Edwin Hang Tong Teo,Changlin Yu ,Jiadong Zhou,Ciqiu Yang ,Xiangwei Huang,Guangtong Liu,Peng Yu,Fucai Liu,Ting Yu,Chao Zhu,Siu Hon Tsang,Zheng Liu

doi:10.1038/s41467-017-00427-5

Abstract

The discovery of monolayer superconductors bears consequences for both fundamental physics and device applications. Currently, the growth of superconducting monolayers can only occur under ultrahigh vacuum and on specific lattice-matched or dangling bond-free substrates, to minimize environment- and substrate-induced disorders/defects. Such severe growth requirements limit the exploration of novel two-dimensional superconductivity and related nanodevices. Here we demonstrate the experimental realization of superconductivity in a chemical vapour deposition grown monolayer material—NbSe2. Atomic-resolution scanning transmission electron microscope imaging reveals the atomic structure of the intrinsic point defects and grain boundaries in monolayer NbSe2, and confirms the low defect concentration in our high-quality film, which is the key to two-dimensional superconductivity. By using monolayer chemical vapour deposited graphene as a protective capping layer, thickness-dependent superconducting properties are observed in as-grown NbSe2 with a transition temperature increasing from 1.0 K in monolayer to 4.56 K in 10-layer.

Highlights

The discovery of monolayer superconductors bears consequences for both fundamental physics and device applications
Superconducting NbSe2 monolayers can only be grown by molecular beam epitaxial (MBE) under ultrahigh vacuum (UHV) and on a dangling bond-free graphene or h-BN substrate[3, 27], in order to minimize environment- and substrate-induced disorders/defects
MBE is expensive to perform because it requires a high-priced apparatus and a UHV environment

Summary

Introduction

The discovery of monolayer superconductors bears consequences for both fundamental physics and device applications. The growth of superconducting monolayers can only occur under ultrahigh vacuum and on specific lattice-matched or dangling bond-free substrates, to minimize environment- and substrate-induced disorders/defects. Such severe growth requirements limit the exploration of novel two-dimensional superconductivity and related nanodevices. By using monolayer chemical vapour deposited graphene as a protective capping layer, thickness-dependent superconducting properties are observed in as-grown NbSe2 with a transition temperature increasing from 1.0 K in monolayer to 4.56 K in 10-layer. Superconducting NbSe2 monolayers can only be grown by molecular beam epitaxial (MBE) under ultrahigh vacuum (UHV) and on a dangling bond-free graphene or h-BN substrate[3, 27], in order to minimize environment- and substrate-induced disorders/defects. MBE is expensive to perform because it requires a high-priced apparatus and a UHV environment

Methods

Results

Conclusion