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Friction Coefficients Derived from Apparent Height Variations in Contact Mode Atomic Force Microscopy Images

1999; American Chemical Society; Volume: 15; Issue: 22 Linguagem: Inglês

10.1021/la981750d

1520-5827

Junwei Li, Chen Wang, Guangyi Shang, Qingmin Xu, Zhang Lin, Jingjiao Guan, Chunli Bai,

Molecular Junctions and Nanostructures

Self-organized monolayer domains of liquid crystal (LC) on mica surface were investigated by contact mode atomic force microscopy (AFM) and friction force microscopy (FFM). By analyzing contributions of friction to the apparent height in AFM height images, we calculated the friction forces and the relevant 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 bare mica were obtained as 0.076 and 0.094, respectively. In addition, frictional asymmetry of LC monolayers was observed in our study, which was attributed 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.