OpticalElement FM-KPFM ring shape LFM sputter Techcomp GaAs TemperatureControl Fendb Battery Worcester_Polytechnic_Institute Annealing PetruPoni_Institute Topography PolymerPatterns Filter Pattern Vinylpyridine HydroGel domain_switching heterojunctions Roughness Hydroxyapatite AM_KPFM MESA structure Piezoelectric Reduction Grain ConductiveAFM VerticalPFM Polypropylene chemical_compound BFO STM Sidewall