Scanning Nonlinear Dielectric Microscopy

Abstract

In this Chapter, we first describe the development of subnanometer-resolution scanning nonlinear dielectric microscopy (SNDM) for the observation of ferroelectric polarization. We demonstrate that the resolution of SNDM is higher than that of conventional piezoresponse imaging. We also describe the theoretical resolution of SNDM and quantitative measurement techniques using SNDM. This theoretical result predicts that an atomic-scale image can be taken by SNDM. Next, we report a new SNDM technique detecting the higher nonlinear dielectric constants ε₃₃₃₃ and ε₃₃₃₃₃. It is expected that higher-order nonlinear dielectric imaging will provide higher lateral and depth resolution. Using this higher-order nonlinear dielectric microscopy technique, we have successfully investigated the surface layers of ferroelectrics. Moreover, a new type of scanning nonlinear dielectric microscope probe, called the ε₃₁₁-type probe, and a system to measure the ferroelectric polarization component parallel to the surface have been developed. Finally, the formation of artificial small, inverted domains is reported to demonstrate that the SNDM system is very useful as a nanodomain engineering tool. Nanosize domain dots were successfully formed in a LiTaO₃ single crystal. This means that we can obtain a very high density of ferroelectric data storage, with a density above 1 Tb/inch². Therefore, we have concluded that SNDM is very useful for observing ferroelectric nanodomains and the local crystal anisotropy of dielectric materials with subnanometer resolution and also has a quite high potential as a nanodomain engineering tool.