Electrode VortexCore SAM Insulator FrequencyModulation HexagonalBoronNitride neodymium_magnets Cobalt-dopedIronOxide Regensburg Hydroxyapatite HDD Lattice piezoelectric force microscopy Polarization Bio SelfAssembly Flake Composition Domain CeNSE_IISc ContactModeDot TPU Array StrontiuTitanate dielectric trench Chemical Vapor Deposition FuelCell Titanate vertical_PFM Materials Sidewall Scratch BiVO4 Granada Wang