Sulfur Fujian lift_mode Step Current KPFM OpticalModulator AmplitudeModulation FM-KPFM Vacuum Metal CeNSE_IISc CarbonNanotube Microchannel P3HT NUS SICM self-assembly SAM Mfm Butterfly light_emitting Graphene INSP HfO2 Anneal GaP Sapphire DLaTGS Writing ForceDistanceSpectroscopy organic_polymer molecular_beam Carbon UTEM