Growth of high quality and large area graphene: Exploitation of liquid substrate
European MRS Meeting 2016, Lille, France
Growth of high qulity and large area graphene or controlling its surface topography still remains challanging. In generally the origin of surface ripples could be associated with the problem of thermodynamic stability of two dimensional membranes, presence of grain boundaries on the substrate and the difference between the thermal expansion coefficients of graphene and substrate. Recently the exploitation of graphene growth on liqufied substrate became a one of the promising trends to address this challenge. Although our studes of graphene growth at elevated temperature by CVD method indeed confirm the elimination of grain boundaries of Cu substrate due to the liquefaction, yet we have observe a new peculiar topographic patterns on the graphene surface in the form of wavy groves and single/double rolls, rough honeycomb cells or their combinations. In-situ SEM studies on liquified Cu substrate suggest that these patterns originate from the dynamic instabilities caused by solutocapillary forces followed by not equilibrium solidification. In the course of graphene growth, these interfacial (Cu-C) instabilities govern the formation of ripples, developing a topographic pattern. These non-equilibrium processes can be well understood based on Mullins-Sekerka and Benard-Marangoni instabilities in diluted binary alloys. The model offer the control parameters over the grown graphene quality such as: imposed carbon concentration gradient, thickness of the melted substrate, quenching rate, diffusivity and dynamic viscosity of carbon in the subtrate and solutal surface tension of the carbon-liquid substrate system.