Image production mechanism for scanning nonlinear dielectric microscopy with super high resolution and its application to quantitative evaluation of linear and nonlinear dielectric properties of ferroelectric materials

Abstract

A theory for scanning nonlinear dielectric microscopy (SNDM) and its application tothe quantitative evaluation of the linear and nonlinear dielectric constants of dielectric materials are described. First, a general theorem for the capacitance variation under an applied electric field is derived and a capacitance variation susceptibility S_nl , which is a very useful parameter for the quantitative measurement of nonlinear dielectric constants, is defined. This S_nl is independent of the tip radius, and therefore the sensitivity of the SNDM probe does not change, even if a tip with a smaller radius is selected to obtain a finer resolution. Using the theoretical results and the data taken by SNDM, the quantitative linear and nonlinear dielectric properties of several dielectric materials were successfully determined. From the calculation of a one-dimensional image of a 180 ° c-c domain boundary, it is demonstrated that the SNDM has an atomic scale resolution.     

Structural and morphological characterization of cerium oxide nanocrystals prepared by hydrothermal synthesis

Colloidal cerium oxide (CeO2) nanocrystals prepared by hydrothermal synthesis were characterized by high-resolution transmission electron microscopy (HRTEM) and three-dimensional electron tomography (3D-ET). HRTEM images of individual CeO2 nanocrystals were then simulated by Blochwave and multislice simulations to determine the atomic arrangement and terminating atoms. The edge length distributions were between 5.0 and 8.0 nm with an average edge length of 6.7 nm. The HRTEM images showed that the CeO2 particles were slightly truncated revealing {220} facets. 3D-ET revealed that the CeO2 nanocrystals exposed predominantly {200} cubic facets. The nanocrystals were truncated at the corners exposing {111} octahedral facets and at the edges {220} dodecahedral facets. Furthermore, 3D-ET revealed the presence of some tetragonal-shaped CeO2 nanocrystals.