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

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.

Thickness-Controlled Growth of Multilayer Graphene on Ni(111) Using an Approximate Equilibrium Segregation Method for Applications in Spintronic Devices

“…The coverage of multilayer graphene (layers ≥3) increases from 77.7% on a 300 nm Ni substrate to 96.3% on a 600 nm Ni substrate using the image gray statistical approach. The coverage of multilayer graphene does not reach the theoretical prediction of 100% due to the actual complicated process of graphene growth, such as the reaction gas etching effect of graphene, nonideal dissolution, and segregation of carbon for the nonuniform layer. The different ways of the dissolution of carbon impurities in the Ni(111) film are implemented, as shown in Figure S3.…”

“…The preparation and characterization of wafer-scale Ni(111) films were described detailed in our previous work. 30,31 The growth of multilayer graphene on Ni(111) film includes two steps. First, the dissolution of carbon impurities in a Ni(111) film was performed by CVD in an atmospheric tube furnace system.…”

Formation of Large-Area Twisted Bilayer Graphene on Ni(111) Film via Ambient Pressure Chemical Vapor Deposition

“…The dominant angle of the peak at 22.7° and 37.3° is consistent with the same superlattice periodicity at angles θ and (60° – θ) of 6-fold symmetric graphene lattice. Iwasaki et al reported that the twist angle θ of bilayer graphene was related to the moiré superlattice periodicity . The twist angle θ = arccos .25em 3 i 2 + 3 i + 1 / 2 3 i 2 + 3 i + 1 and superlattice periodicity L = a 3 i 2 + 3 i + 1 , where a = 2.46 Å is the lattice parameter of graphene and i takes on the values 1, 2, 3, ...…”

“…Iwasaki et al reported that the twist angle θ of bilayer graphene was related to the moirésuperlattice periodicity. 42 The twist angle arccos…”

“…Then, the wafer-scale single-crystalline Ni(111) film was obtained by annealing at a high temperature in the atmospheric tube furnace or ultrahigh-vacuum (UHV) system. The preparation and characterization of Ni(111) films were described in detail in our previous work. , The prepared Ni(111) films were then loaded into atmospheric quartz tube in a gas flow of H 2 (10 sccm) and Ar (50 sccm) for the TBG growth at 850 °C. First, CH 4 at a gas flow of 1 sccm was introduced into the chamber for the nucleation and growth of monolayer graphene domains, utilizing the catalytic dehydrogenation reaction of CH 4 .…”