Effect of the surface adsorbed water on the studying of ferroelectrics by scanning nonlinear dielectric microscopy

The effect of adsorbed water on the signal of scanning nonlinear dielectric microscopy (SNDM) is reported. By measuring SNDM image variation under various measurement conditions and by computing the theoretical SNDM signal corresponding to these conditions, we verified that the adsorbed water strongly affects the signal strength, depth sensitivity, and resolution of SNDM. From this study, we find that it is necessary to consider adsorbed water for detailed measurement of the surface polarization state by SNDM. In addition, we also confirmed that the surface paraelectric layer on a LiTaO3 single crystal grows upon heat treatment.