Applied Surface Science, Vol.399, 542-550, 2017
Evolution effects of the copper surface morphology on the nucleation density and growth of graphene domains at different growth pressures
In this work, we study the influence of the surface morphology of the catalytic copper substrate on the nucleation density and the growth rate of graphene domains at low and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) processes. In order to obtain a wide range of initial surface morphology, precisely controlled electropolishing methods were developed to manipulate the roughntreess value of the as-received Cu substrate (RMS=30 nm) to ultra-rough (RMS= 130 nm) and ultra-smooth (RMS= 2 nm) surfaces. The nucleation and growth of graphene domains show obviously different trends at LPCVD and APCVD conditions. In contrast to APCVD condition, the nucleation density of graphene domains is almost equal in substrates with different initial roughness values at LPCVD condition. We show that this is due to the evolution of the surface morphology of the Cu substrate during the graphene growth steps. By stopping the surface sublimation of copper substrate in a confined space saturated with Cu atoms, the evolution of the Cu surface was impeded. This results in the reduction of the nucleation density of graphene domains up to 24 times in the pre-smoothed Cu substrates at'LPCVD condition. (C) 2016 Elsevier B.V. All rights reserved.
Keywords:Cu surface morphology;Electropolishing;Graphene CVD growth;Nucleation density;Surface evolution;Growth pressure