Piezoresponse Yeditepe_University biocompatible HfO2 atomic_steps mfm_amplitude Yeditepe Sapphire IIT-chennai BismuthFerrite Croatia DataStorage hetero_structure MolecularSelfAssembly HexagonalBN high_resolution TiO2 SmalScan Fet Sidewall Laser Phthalocyanine Phase Sio2 LithiumNiobate SurfaceOxidation #Materials Mechanical&nanotechnology STM exfoliate SRAM ScanningKelvinProbeMicroscopy Au111 Piezoelectric kelvin probe force microscopy