Scanning nonlinear dielectric microscopy and its use in next‐generation ultrahigh‐density ferroelectric data storage

We have developed a high-resolution scanning nonlinear dielectric microscope that can provide imaging with subnanometer resolution of domain structure in the polarization of ferroelectrics. Using this microscope, we were able to image several types of domain structures in ferroelectric materials. Moreover, because nonlinear dielectric responses of any order can be used for imaging, and because it is simple to vary the order used, our nonlinear dielectric constant microscope has higher-order modes of operation, whose use improves the resolution of the microscope. In addition, the configuration of our microscope allows us to image the polarization in the direction parallel to the sample surface by suitably rotating the direction of the applied electric fields. This imaging is possible because the microscope yields information about the full third-order nonlinear dielectric constant tensor. In the course of exploring ways to apply this microscope technology to next-generation ultrahigh-density ferroelectric data storage, we have recently shown data storage at densities of 1.5Tbit/in2, which is the world's highest storage density in a rewriteable storage medium. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 89(1): 19–31, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20170