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Scanning Probe Microscopy (SPM) based techniques probe material properties over microscale regions with nanoscale resolution, ultimately resulting in investigation of mesoscale functionalities. Among SPM techniques, piezoresponse force microscopy (PFM) is a highly effective tool in exploring polarization switching in ferroelectric materials. However, its signal is also sensitive to sample‐dependent electrostatic and chemo‐electromechanical changes. Literature reports have often concentrated on the evaluation of the Off‐field piezoresponse, compared to On‐field piezoresponse, based on the latter's increased sensitivity to non‐ferroelectric contributions. Using machine learning approaches incorporating both Off‐ and On‐field piezoresponse response as well as Off‐field resonance frequency to maximize information, switching piezoresponse in a defect‐rich Pb(Zr,Ti)O3 thin film is investigated. As expected, one major contributor to the piezoresponse is mostly ferroelectric, coupled with electrostatic phenomena during On‐field measurements. A second component is electrostatic in nature, while a third component is likely due to a superposition of multiple non‐ferroelectric processes. The proposed approach will enable deeper understanding of switching phenomena in weakly ferroelectric samples and materials with large chemo‐electromechanical response. [ABSTRACT FROM AUTHOR]

Piezoresponse force spectroscopy (PFS) has emerged as a powerful technique for probing highly localized polarization switching in ferroelectric materials. The application of a dc bias to a scanning probe microscope tip in contact with a ferroelectric surface results in the nucleation and growth of a ferroelectric domain below the tip, detected though the change of local electromechanical response. Here, we analyze the signal formation mechanism in PFS by deriving the main parameters of domain nucleation in a semi-infinite ferroelectric semiconductor material. The effect of surface screening and finite Debye length on the switching behavior is established. We predict that critical domain sizes and activation barrier in piezoresponse force microscopy (PFM) is controlled by the screening mechanisms. The relationships between domain parameters and PFM signal is established using a linear Green’s function theory. This analysis allows PFS to be extended to address phenomena such as domain nucleation in the vicinity of defects and local switching centers in ferroelectrics. [ABSTRACT FROM AUTHOR]

Kelvin probe force microscopy (KPFM) is a widely used technique to map surface potentials at the nanometer scale. In traditional KPFM, a feedback loop regulates the DC bias applied between a sharp conductive probe and a sample to nullify the electrostatic force (closed-loop operation). In comparison, open-loop techniques such as dual harmonic KPFM (DH-KPFM) are simpler to implement, are less sensitive to artefacts, offer the unique ability to probe voltage sensitive materials, and operate in liquid environments. Here, we directly compare the two techniques in terms of their bandwidth and sensitivity to instrumentation artefacts. Furthermore, we introduce a new correction for traditional KPFM termed "setpoint correction," which allows us to obtain agreement between open and closed-loop techniques within 1%. Quantitative validation of DH-KPFM may lead to a wider adoption of open-loop KPFM techniques by the scanning probe community. [ABSTRACT FROM AUTHOR]

An approach for high-frequency transport imaging, referred to as scanning frequency mixing microscopy (SFMM), is developed. Application of two high-frequency bias signals across an electroactive interface results in a low-frequency component due to interface nonlinearity. The frequency of a mixed signal is chosen within the bandwidth of the optical detector and can be tuned to the cantilever resonances. The SFMM signal is comprised of an intrinsic device contribution and a capacitive mixing contribution, and an approach to distinguish the two is suggested. This technique is illustrated on a model metal-semiconductor interface. The imaging mechanism and surface-tip contrast transfer are discussed. SFMM allows scanning probe microscopy based transport measurements to be extended to higher, ultimately gigahertz, frequency regimes, providing information on voltage derivatives of interface resistance and capacitance, from which device characteristics such as Schottky barrier height, etc., can be estimated. [ABSTRACT FROM AUTHOR]