kelvin probe force microscopy FM-KPFM FastScan non_contact align SingleCrystal Reading nanobar Oxide Typhimurium NiFe Pzt Polystyrene Zhi AtomicSteps TemperatureControl UnivMaryland thermal_property DeoxyribonucleicAcid Biofilm Ca10(PO4)6(OH)2 Polyvinylidene_fluoride MagneticForce Ni81Fe19 Molybdenum PatternedSapphireSubstrat solar_cell SurfaceChange Adhesion FFM HOPG HDD ULCA CNT Pattern