Quantification of phase and amplitude response by piezoresponse force microscopy

The manifestation of a polarization versus electric field hysteresis loop is a distinctive feature of ferroelectricity. However, this can also easily arise from experimental artifacts. Therefore, the misinterpretation of loops arising from surface artifacts can mislead the obtained outcomes when used as evidence for ferroelectric behavior. The identification of accurate ferroelectric response becomes more complicated when the measurement is performed at the nanoscale by piezoresponse force microscopy (PFM), a powerful technique to characterize and manipulate ferroelectric domains. Although the switching spectroscopy-PFM (SS-PFM) technique has received significant attention for quantifying the electromechanical (EM) response, accurate PFM image processing and its consequence on the quantification of EM response has not received much attention so far. In this presentation, we will describe how to obtain artifact-free PFM phase and amplitude images from ferroelectric materials. The difference between the images containing intrinsic and non-intrinsic responses will be identified by post-imaging analysis. Furthermore, the EM response obtained by the SS-PFM technique under different read voltages (e.g., -3 to +3 V) will be discussed. A rigorous technique for the selection of the genuine EM response out of the obtained SS-PFM loops will be identified after obtaining the average surface potential of the sample by the Kelvin probe force microscopy (KPFM). Therefore, through this we demonstrate that the combined SS-PFM and KPFM techniques will eventually aid in deciding the correct EM response of ferroelectric materials. Overall, the properly calibrated PFM phase and amplitude signals (imaging and spectroscopy) can provide valuable information from ferroelectric domains at the nanoscale and can differentiate the response between the true ferroelectrics and ionic conductors or other artifacts.