Piezoresponse-Force Microscopy

Aerospace has developed and successfully applied piezoresponse-force microscopy techniques for nanoscale characterization of the phase contrasts of nonferroelectric and ferroelectric domains in thin-film and bulk dielectric substrates. Piezoresponse-force microscopy permits direct imaging of ferroelectric domain structures with resolution on the order of 3 to 10 nanometers. Traditional atomic-force microscopes can be augmented and tailored for specific operational modes like piezoresponse-force microscopy, where the mechanical response of the sample is measured during local electrical excitation by the microscope probe tip. A modulated ac voltage is applied between the underlying substrate and conductive microscope tip during contact-mode scanning. Using lock-in amplifier techniques, the local electromechanical displacement can be decoupled from the topographical displacement via the phase shift between the rapidly oscillating ac field and the slow cantilever displacement feedback. The static cantilever deflection corresponds to the surface profile variations and topography, while the modulated cantilever oscillations are related to the piezoelectric response of the sample. Additionally, piezoresponse-force microscopy allows for the simultaneous acquisition of data corresponding to out-of-plane distortions (where the polarization is normal to the surface) as well as in-plane or lateral distortions (where the polarization is parallel to the surface).

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