Electrostatic contribution to hysteresis loop in piezoresponse force microscopy

In piezoresponse force microscopy (PFM), ideally, electromechanical strain is induced only by the converse piezoelectric effect. In reality, however, the obtained experimental PFM signal is a combination of many other factors. In particular, the concurrent electrostatic effect between the tip/cantilever and a sample surface can be significant because the electrostatic effect induced by surface potential is inevitable in some cases. However, most previous reports dealt with the extreme case of the electrostatic effect, such as the on-field state. That is, the contributions to the hysteresis loop of electrostatic effects from different sources have not yet been clearly understood. In the present work, we study the electrostatic effect on the hysteresis loop in relation to various measurement parameters. The results indicate that the PFM response is strongly affected by the electrostatic effect caused by external charge injection. This work can provide a guideline for determining the PFM response in a hysteresis loop.