Varistor NUS_Physics MetalCompound vertical_PFM NUSNNI Hafnia Pyroelectric pulsed_laser_deposition STO Molybdenum Boundary ForceMapping Gallium Barium_titanate PpLdpe KPFM Ecoli C60H122 Step AnodizedAluminumOxide sputter Multiferroic_materials Ananth StainlessSteel polyvinyl acetate Switching CeNSE_IISc piezoelectric force microscopy DNA MolecularSelfAssembly FailureAnalysis H-BN Workfunction domain_switching HanyangUniv