Beads kelvin probe force microscopy InsulatorFilm neodymium_magnets Glass UnivOfMaryland temperature controller AFM Ananth UnivMaryland Boundary hetero_structure BoronNitride TungstenThinFilmDeposition Magnetic CBD light_emitting TipBiasMode Nanopattern FloppyDisk PvdfBead LiftMode silicon_carbide GalliumPhosphide pinpoint mode LateralForce INSPParis Worcester_Polytechnic_Institute Co/Cr/Pt mechanical property Butterfly HexacontaneFilm Chromium ElectrostaticForceMicroscopy Copper PDMS