Controlled Epitaxial Growth and Atomically Sharp Interface of Graphene/Ferromagnetic Heterostructure via Ambient Pressure Chemical Vapor Deposition.

Ruinan Wu,Jiayu Dai,Guang Wang,Qi Zhang,Peisen Li,Junping Peng,Dixiang Chen,Yueguo Hu,Xiangnan Xie,Yanrui Guo,Weicheng Qiu,Jiafei Hu,Ming Yang,Mengchun Pan

doi:10.3390/nano11113112

Abstract

The strong spin filtering effect can be produced by C-Ni atomic orbital hybridization in lattice-matched graphene/Ni (111) heterostructures, which provides an ideal platform to improve the tunnel magnetoresistance (TMR) of magnetic tunnel junctions (MTJs). However, large-area, high-quality graphene/ferromagnetic epitaxial interfaces are mainly limited by the single-crystal size of the Ni (111) substrate and well-oriented graphene domains. In this work, based on the preparation of a 2-inch single-crystal Ni (111) film on an Al2O3 (0001) wafer, we successfully achieve the production of a full-coverage, high-quality graphene monolayer on a Ni (111) substrate with an atomically sharp interface via ambient pressure chemical vapor deposition (APCVD). The high crystallinity and strong coupling of the well-oriented epitaxial graphene/Ni (111) interface are systematically investigated and carefully demonstrated. Through the analysis of the growth model, it is shown that the oriented growth induced by the Ni (111) crystal, the optimized graphene nucleation and the subsurface carbon density jointly contribute to the resulting high-quality graphene/Ni (111) heterostructure. Our work provides a convenient approach for the controllable fabrication of a large-area homogeneous graphene/ferromagnetic interface, which would benefit interface engineering of graphene-based MTJs and future chip-level 2D spintronic applications.

Highlights

IntroductionThe long spin-relaxation length and strong spin filtering effect have proven that graphene is an emerging material for two-dimensional (2D) spintronics [1–5]
The analysis shows thatshows the initial density is an important important factor in growing uniform monolayer graphene [20]
The optimal growth method is sucachieved by making a tune of the well-oriented nucleation process of the Ni (111) catalytic cessfully achieved by making a tune of the well-oriented nucleation process of the Ni

Summary

Introduction

The long spin-relaxation length and strong spin filtering effect have proven that graphene is an emerging material for two-dimensional (2D) spintronics [1–5]. The strong spin filtering effect at the lattice-matched graphene/Ni (111) interface has been theoretically predicted and experimentally studied [6,7] and results in an extreme TMR in vertical graphene/ferromagnetic (FM) spintronic devices [8–10]. The performance of graphene-based spintronic devices largely depends on the quality of the graphene/FM interface, and it is a great challenge to controllably achieve large-size homogenous graphene/FM heterostructures with a well-oriented interface. Grown graphene (EGG) on single-crystal ferromagnetic metals via chemical vapor deposition (CVD) has been widely reported. Dahal [12] synthetized uncontrolled multilayer graphene on single-crystal NiFe (111) and Ni (111)/Y2 O3

Methods

Results

Conclusion