VortexCore KPFM hard_disk_media Gold Ca10(PO4)6(OH)2 Composition AmplitudeModulation pinpoint mode Polyethylene BiVO4 vertical_PFM LiBattery PinpointPFM Terrace PECurve mechanical_property LaAlO3 F14H20 fluoroalkane Beads temp_control Defects FM_SKPM EPFL CHRYSALIS_INC Ecoli PinpointNanomechanicalMode Corrosion small_scan ForceMapping Polystyrene ElectrostaticForceMicroscopy PrCurve 2d_materials LiquidImaging