▎ 摘　　要

Quantitative atomic force microscope (AFM) measurements are performed by using both unmodified and octadecyltrichlorosilane self-assembled monolayers (OTS-SAMs)-functionalized AFM silicon (Si) tips in contact with the uncoated SiO2 substrate, OTS-SAMs coated SiO2 substrate and SiO2 substrate with graphene (Gr) sheet on its surface, providing six pairs of frictional interfaces. Drastic differences in the adhesion and friction responses of these six pairs of friction interfaces are observed. Lower adhesion force and friction force occur with OTS-SAMs coated on either tips or substrates, and the friction force is ultralow when Gr presented on the substrate with OTS-coated tips sliding against it. The observed ultralow friction is attributed to the hydrophobicity and incommensurate contact between Gr and OTS-SAMs. This work has important impact on designing approaches of friction pairs to achieve ultralow friction.