Raman spectroscopy and imaging of Bernalstacked bilayer graphene synthesized on copper foil by chemical vapour deposition: growth dependence on temperature

Abstract

We report on the effect of temperature on the growth of bilayer graphene on a copper foil under atmospheric pressure chemical vapour deposition (AP-CVD). Before characterization of the AP-CVD bilayer graphene, a high-quality graphene flake was obtained from the Kish bulk graphite by micro-mechanical exfoliation and characterized by using Raman spectroscopy and imaging. The Raman data of the exfoliated, high-quality graphene flake show monolayer and bilayer graphenes and were compared with the Raman data of AP-CVD graphene. Raman spectroscopy of AP-CVD graphene shows bilayer films that exhibit predominantly Bernal stacking with an I2D/IG ratio of ~1. At low growth temperature (~780 °C), Raman disorder-related peak intensity in the AP-CVD graphene is high and decreases with an increase in growth temperature to the lowest disorder intensity at ~973 °C. The selected area electron diffraction and atomic force microscopy average step height analysis showed the thickness of the bilayer graphene. The AP-CVD graphene is uniform at low growth temperatures (~780 °C) with a high disorder and becomes nonuniform at high growth temperatures (~867–973 °C) with a very low disorder as bilayer graphene evolves to form islands with an average lateral size of <10 μm. Competition between carbon adatoms supply through dehydrogenation of the CHx species, mobility and desorption rate of the carbon-adatom species for nucleation of the bilayer graphene as a function of temperature is elucidated. This study provides further insight into the growth mechanisms of bilayer graphene by AP-CVD on Cu.