National Institute of Standards and Technology,
Keywords: characterization, scanning probe microscopy
Summary:Piezoresponse for microscopy (PFM) has become a ubiquitous method for the nanoscale measurement of ferroelectric properties and numerous related electromechanical phenomena. However, to date, quantification of properties in PFM has often been hampered by artifacts related to background electrostatic forces, mechanical property variations of the sample, and complex cantilever dynamics. Significant instrument hardware upgrades have addressed some of these limitations, but access to those upgrades by most users has been limited. Here, we discuss recent innovations in PFM that can be readily implemented on nearly all microscopes currently deployed in the field. First, we discuss electrostatically blind piezoresponse force microscopy, wherein precise positioning of the detection laser on the cantilever allows separation of desired PFM response from undesired background electrostatics. By measuring with the electrostatic blind spot (ESBS), quantitative coupling coefficients, artifact-free switching spectroscopy, and precise mapping of domain boundaries are enabled. We complement the ESBS work with recent progress in contact-resonance amplified PFM (CR-PFM). Traditionally, CR-PFM has demanded a trade off wherein achieving superior sensitivity meant a lack of quantification and an acceptance of numerous other artifacts. By calibrating the CR-PFM signal, and employing new forms of CR frequency control, we can now perform quantitative CR-PFM with sensitivity to ~100 fm electromechanical strains. Combined, these recent advances in sub-resonance and contact resonance PFM give more users than ever the ability to perform reliable electromechanical measurements.