Temperature-dependent friction coefficient on flat graphite plane

Abstract

Investigating the frictional properties of two-dimensional layered materials with dynamic evolution of contact quality advances understanding the mechanism underlying puckering effects, offering a new pathway for the rational control of friction. In this letter, friction force microscopy (FFM) in ultra-high vacuum (UHV) conditions has been used to probe the nanoscale friction on a freshly cleaved flat graphite surface (0001) as a function of normal force and surface temperature. It is found that friction force shows a nonmonotonic change with the decrease of temperature with the maximum friction appeared around Tmax=140±5 K. Besides, coefficients of friction (COFs) defined as the slope of friction-normal force curves remains nearly constant before the friction peak while surprisingly change into negative values with the further decrease of temperature. The loading–unloading results reveal that, the abnormal COFs behavior originates from the temperature induced contact quality evolution which leads to the ripple formation at cryogenic temperatures in the front of scanning tip. The results reported here provide a deep insight into the effects of temperature on the frictional behaviors of graphite, which give a new thrust in the field of friction on lamellar materials.