Gain and Scan Rate Dependence of Friction at the Nanoscale Measured by Lateral Force Microscopy

Lateral force microscopy (LFM) is used to examine friction at the nanoscale. Although the friction at the tip-sample contact measured by LFM can provide extensive information beyond the friction force itself, such as the crystallographic orientation, the presence of defects, etc., there have been many contradictory reports regarding friction coefficients, nanoscale friction laws, etc. obtained by this technique. Here we investigate the effect of scan rate and gain on the LFM frictional force measurements. We show that the ratio of friction measured on SiO2 to friction measured on graphene can vary from about 1 to approximately 9.2 depending on the combination of these parameters. We discuss how to optimize the associated scan parameters to obtain reliable friction data at the nanoscale.