Thermodynamics and kinetics of graphene growth on SiC(0001)

The formation of surface phases on the Si-terminated SiC(0001) surface, from the Si-rich (3x3) structure, through the intermediate (1x1) and (sqrt[3]xsqrt[3])-R30 degrees structures, to the C-rich (6sqrt[3]x6sqrt[3]) phase, and finally epitaxial graphene, has been well documented. But the thermodynamics and kinetics of these phase formations are poorly understood. Using in situ low energy electron microscopy, we show how the phase transformation temperatures can be shifted over several hundred degrees Celsius, and the phase transformation time scales reduced by several orders of magnitude, by balancing the rate of Si evaporation with an external flux of Si. Detailed insight in the thermodynamics allows us to dramatically improve the morphology of the final C-rich surface phases, including epitaxial graphene.