Friction coefficients derived from apparent height variations in contact mode atomic force microscopy images

Self-organized monolayer domains of liquid crystal(LC)on mica surface were investigated by contact mode atomic force microscopy (AFM) and friction for ce microscopy (FFM). By analyzing contributions of friction to the apparent height in AFM height images, we calculated the friction forces and the rel evant friction coefficients. It is observed that the difference between the magnitude of the friction force on LC monolayers and mica was proportional to the normal load. The friction coefficients of the LC monolayers and bar e mica were obtained as 0.076 and 0.094, respectively. In addition, frictio nal asymmetry of LC monolayers was observed in our study, which was attribu ted to the molecular tilt, and a possible explanation was proposed in terms of the stick-slip motion of the tip apex on the molecular scale.