FrictionalForce 2dMaterials Step Gallium_Arsenide Beads PS_LDPE PhaseTransition FM-KPFM Optoelectronic alkanes Sapphire WS2 GaP CP-AFM SmallScan LiBattery ImideMonomer Tin sulfide CntFilm Polypropylene HanyangUniv PhaseImaging Phosphide Ram ReflexLens blended polymers GlassTemperature WPlug KPFM HiVacuum Workfunction HexagonalBN polyvinyl acetate Lateral_Force_Microscopy Adhesive