Biology bias_mode TungstenDeposition FM_SKPM INSP Vacuum SICM flakes Polypropylene PhaseChange Gallium Fluoride Alkane UnivCollegeLondon FrictionalForce layers TappingMode Electrode PECurve self_assembly FastScan Perovskite LDPE Microchannel EFMAmplitude Vac SingleLayer FuelCell Friction Piezo pinpoint mode HafniumDioxide hard_disk_media SAM HexagonalBN