Synthesis of large-area rhombohedral few-layer graphene by chemical vapor deposition on copper

TL;DR

This study reports the successful synthesis of large-area, multi-layer rhombohedral graphene via chemical vapor deposition on copper, enabling exploration of its unique electronic properties and potential applications.

Contribution

It introduces a CVD method to grow rhombohedral graphene up to 9 layers thick and 50 micrometers in size, overcoming previous limitations in material isolation.

Findings

Rhombohedral FLG domains alternate with Bernal-stacked domains within the same crystal.

Formation of rhombohedral FLG is strongly influenced by copper substrate morphology.

Growth process enables larger, thicker rhombohedral graphene suitable for physics and device studies.

Abstract

Rhombohedral-stacked few-layer graphene (FLG) has been receiving an ever-increasing attention owing to its peculiar electronic properties that could lead to enticing phenomena such as superconductivity and magnetic ordering. Up to now, experimental studies on such material have been mainly limited by the difficulty in isolating it in thickness exceeding 3 atomic layers with device-compatible size. In this work, rhombohedral graphene with thickness up to 9 layers and areas up to ~50 micrometers square is grown via chemical vapor deposition (CVD) on suspended Cu foils and transferred onto target substrates via etch-free delamination. The domains of rhombohedral FLG are identified by Raman spectroscopy and are found to alternate with domains of Bernal-stacked FLG within the same crystal in a stripe-like configuration. A combined analysis of micro-Raman mapping, atomic force microscopy and optical microscopy indicates that the formation of rhombohedral-stacked FLG is strongly correlated to the copper substrate morphology. Cu step bunching results in bending of FLG and interlayer displacement along preferential crystallographic orientations, as determined experimentally by electron microscopy, thus inducing the stripe-like domains. The growth and transfer of rhombohedral FLG with the reported thickness and size shall facilitate the observation of predicted unconventional physics and ultimately add to its technological relevance.