PinpointPFM BiVO4 Sapphire membrane Nanopattern ring shape heterojunctions Vacuum Cobalt-dopedIronOxide Stiffness Blend Deposition fluoroalkane PtfeFilter Tin sulfide Growing Iron TPU light_emission MESA structure Pyroelectric Heating Temperature mono_layer InorganicCompound PhaseTransition domain_switching HexagonalBN medical LateralPFM Regensburg STM MetalCompound FM_KPFM bias_mode