Experimental and theoretical studies on the surface morphology variation of a Ni substrate by graphene growth

Junro Takahashi,Yoshikazu Homma,Hiroki Kato,Tomoyuki Ueyama,Kazuhito Kamei

doi:10.1063/5.0036580

Junro Takahashi, Yoshikazu Homma + Show 3 more

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https://doi.org/10.1063/5.0036580

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Abstract

As graphene grows on a metal substrate, step bunching and terrace formation occur due to thermodynamic instability. Variation in the terrace–step bunching morphology is caused by graphene–metal interaction. The mechanism for this morphological variation was elucidated in terms of the crystal lattice matching by the observation of step bunching formation using in situ scanning electron microscopy and analysis of the crystal orientation of the same microscopic field using electron backscatter diffraction. The cross-sectional structure was also observed using transmission electron microscopy (TEM). These combined methods enable a reliable analysis of the step bunching region. The lattice matching was also evaluated according to the 0-lattice theory. From the structural analysis using TEM and the application of the 0-lattice theory, the graphene-covered surface was confirmed to consist of good and poor lattice-matching regions. The steps ejected from the terrace region piled up in the poor lattice-matching region to form a low Miller index plane. It was concluded that step flow occurs on the good lattice-matching region and steps are piled up and arranged very closely on the poor matching region based on the lattice-matching evaluation by the 0-lattice theory.

Highlights

A number of studies have reported that graphene grown on metal substrates induced marked step bunching, which initiated the faceting of the substrate.[1,2,3,4,5,6,7,8,9] The band structure of graphene grown on a terrace is different from that grown on a bunched step region,[6] and this difference is expected to be utilized for band engineering
The mechanism for this morphological variation was elucidated in terms of the crystal lattice matching by the observation of step bunching formation using in situ scanning electron microscopy and analysis of the crystal orientation of the same microscopic field using electron backscatter diffraction
The cross-sectional structure was observed using transmission electron microscopy (TEM). These combined methods enable a reliable analysis of the step bunching region

Summary

Introduction

A number of studies have reported that graphene grown on metal substrates induced marked step bunching, which initiated (and accompanied) the faceting of the substrate.[1,2,3,4,5,6,7,8,9] The band structure of graphene grown on a terrace is different from that grown on a bunched step region,[6] and this difference is expected to be utilized for band engineering. The band structure of graphene nanoribbons is dependent on their width and structure, and the engineering of terrace–step bunching structures (wrinkle engineering) is advantageous for electronic engineering. The control of terrace–step bunching structures is very important in the industrial use of graphene

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