Towards growth of high quality and large area graphene: Exploitation of liquid substrate - Towards growth of high quality and large area graphene: Exploitation of liquid substrate - HRI-US
Towards growth of high quality and large area graphene: Exploitation of liquid substrate
Growth of high qulity and large area graphene or control of its surface topography still remain challanging. The origin of surface ripples of graphene 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 a substrate. Recently the exploitation of graphene growth on liqufied substrate became one of the promising trends to address this challenge [1-3]. Our studies of graphene growth at elevated temperature by CVD method confirm not only the elimination of grain boundaries of Cu substrate due to liquefaction, but we have also observed new peculiar topographic patterns on the graphene surface in the form of wavy groves and single/double rolls, rough honeycomb cells, or combinations of both . In-situ SEM studies on liquified Cu substrate suggest that these patterns originate from the dynamic instabilities caused by solutocapillary forces followed by non 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 offers 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.