Effect of temperature on the diffusion coefficient and kinetic friction of the C60/graphene system. (a) The Arrhenius analysis of the surface diffusion coefficient, D, of the C60 indicates the existence of two diffusive regimes with a crossover around 75 K. The inset of (a) illustrates that the friction coefficient decreases from 1.3 ps-1 to a value in the order of 0.01 ps-1 when the temperature is increased from 25 to 200 K. (b) Mean square displacement (MSD) of C60 motion as a function of time at 50 and 125 K. Note that at 50 K, the MSD grows linearly with time, consistent with quasi-continuous Brownian motion. At 150 K, the MSD is initially parabolic for time shorter than 1/η, consistent with ballistic-like Brownian motion.
Jafary-Zadeh et al. Nanoscale Research Letters 2012 7:148 doi:10.1186/1556-276X-7-148