Nanotribological behavior of C-60 films at an extremely low load

We have studied the nanotribological behavior of C-60 films formed on a KCl (001) surface at an extremely low load, using scanning force microscopy (SF M). It has been observed that the SFM tip undergoes molecularly resolved st ick-slip motion depending on scanning direction. The frictional force at th e relative humidity (RH) of 20% is about a quarter that in dry argon. The d ecrease in frictional force at 20% RH comes from the lower stiffness of the tip-sample contact, indicating the mobility of C-60 molecules, such as rol ling and/or translation due to water adsorption. (C) 1999 Elsevier Science B.V. All rights reserved.