kelvin probe force microscopy Jason Defects HDD AnodizedAluminumOxide Hair semifluorinated_alkanes Yttria_stabilized_Zirconia atomic_steps LateralPFM ScanningTunnelingMicroscopy SrO HOPG optoelectronics Typhimurium Workfunction Korea Collagen Silicon SKKU Phosphide AIN PFM temp Stiffness fluoroalkane ConductiveAFM Polymer Edwin FrictionalForce Mobile Pvdf strontiu_titanate BiasMode NUS