Asymmetric Growth of Tetragon-Shaped Single-Crystalline Graphene Flakes on Copper Foil by Annealing Treatment under Oxygen-Free Conditions

Abstract

Engineering graphene into a particular shape is vital for potential industrial applications. To this end, better understanding of the growth mechanism is needed to control the growth behavior of graphene on a substrate surface with a specific shape. In this work, a tetragon-shaped graphene single crystal (TS_GSC) with millimeter-scale grain size was achieved on copper foil, which was annealed at oxygen-free conditions (AOF) prior to graphene growth. The TS_GSC grains are featured by two dendritic Frontiers at the shorter-edge (SE) sides and two sharp Frontiers at the longer-edge (LE) sides of graphene grain. By combining scanning electron microscopy, optical microscopy, and Raman mapping with carbon isotope labeling, we revealed for the first time an asymmetric growth behavior of TS_GSC grains on an AOF-treated copper substrate. It was supposed that the growth of graphene was determined by the diffusion-limited aggregation mechanism at the SE side, whereas it was governed by the edge-determined atom-attachment mechanism at the LE side of graphene grain. In addition to single-layer graphene, tetragon-shaped bilayered graphene with grain size over 200 μm was also achieved on the AOF-treated copper substrate.

Vertical-Graphene-Assisted Chemical Vapor Deposition for Fast Growth of Macroscaled Graphene Grains

“…A mixed gas of hydrogen (H 2 ) with a flow rate of 50 sccm and Ar with a flow rate of 300 sccm was inlet into the CVD chamber during the whole growth process, while methane (CH 4 ) with a flow rate of 0.5 sccm was only inlet at the growth stage. Graphene was transferred onto a silicon wafer with the assistance of polymethyl methacrylate which is well documented in the literature. , For characterization, a Zeiss Axio optical microscope and a Zeiss Sigma 300 scanning electron microscope were used to obtain optical microscopy (OM) and scanning electron microscopy (SEM) images, respectively. The Raman spectra and Raman maps were obtained on a Horiba HR Evolution Raman spectrometer using a laser excitation of 532 nm.…”

“…Graphene was transferred onto a silicon wafer with the assistance of polymethyl methacrylate which is well documented in the literature. 52,53 For characterization, a Zeiss Axio optical microscope and a Zeiss Sigma 300 scanning electron microscope were used to obtain optical microscopy (OM) and scanning electron microscopy (SEM) images, respectively. The Raman spectra and Raman maps were obtained on a Horiba HR Evolution Raman spectrometer using a laser excitation of 532 nm.…”

Characterization and Manipulation of Carbon Precursor Species during Plasma Enhanced Chemical Vapor Deposition of Graphene

“…Currently, most high quality, large area graphene is produced via chemical vapor deposition (CVD) techniques with gaseous hydrocarbon precursors, micrometer scale Cu as a catalyst and support, and synthesis temperatures in excess of 900 °C [ 1 , 2 , 3 , 4 , 5 ]. Due to the relative thickness and composition of the catalyst and elevated synthesis temperatures, these growths require a transfer process to the target substrate which limits incorporation of graphene to applications with only planar geometries.…”