High-precision local C–V mapping for ferroelectrics using principal component analysis

Abstract

Local C-V mapping based on scanning nonlinear dielectric microscopy (SNDM) is a useful tool for characterizing ferroelectric domain dynamics at the nanoscale. In this study, we realized high-precision C-V mapping through an improved measurement system that introduces a digitizer and post-signal processing. Coupled with the high capacitance detection sensitivity of SNDM, nontrivial patterns corresponding to the polarization response were observed even in harmonic images with an order as high as thirty. Using these high-order harmonic components for the C-V curve resynthesis led to improved measurement accuracy. In addition, further improvement was achieved by introducing noise reduction based on principal component analysis. From the C-V curves resynthesized in this manner, parameters that represent the curve features could be extracted and subsequently displayed in two-dimensional maps. Detailed analyses of the datasets obtained with a ferroelectric HfO 2 film revealed interesting distributions concerning local polarization switching dynamics.

Nanoscale mapping to assess the asymmetry of local C–V curves obtained from ferroelectric materials

“…An example of data obtained from local C-V mapping of a HfO 2 -based ferroelectric thin film 18) is presented in Ref. 14. The present work continued the analysis of the experimental dataset obtained in this previous study.…”

“…The present study demonstrates visualization of asymmetric domain switching in real space with high resolution using the local capacitance-voltage (C-V ) mapping method which was recently developed by our group. 13,14)…”

Data-Driven Analysis of High-Resolution Hyperspectral Image Data Sets through Nanoscale Capacitance–Voltage Measurements to Visualize Ferroelectric Domain Dynamics

“…The local C−V data set for polycrystalline HfO 2 -based ferroelectric thin films analyzed in this study was obtained from a previous study. 29 To obtain this data set, the response signal of capacitance change to an AC bias of 12 V pp was measured at each point of a 256 × 128 grid in a 4 μm × 2 μm area of a polycrystalline Y:HfO 2 film with a thickness of 17.5 nm (see the Methods section for deposition conditions). The response waveforms obtained at each point were then subjected to Fourier series expansion, and the Fourier coefficients corresponding to the 1 to 30ω harmonics were calculated.…”

“…The correlation between the real-space distribution of polarization switching properties, including the net amount of switching polarization, switching voltage, and local imprint, as obtained by local C−V mapping, and the grain structure of the polycrystalline film provides new insights into the wake-up mechanism for thin films that cannot be obtained by conventional methods. In turn, such an approach should 29 To obtain this data set, the response signal of capacitance change to an AC bias of 12 V pp was measured at each point of a 256 × 128 grid in a 4 μm × 2 μm area of a polycrystalline Y:HfO 2 film with a thickness of 17.5 nm (see the Methods section for deposition conditions). The response waveforms obtained at each point were then subjected to Fourier series expansion, and the Fourier coefficients corresponding to the 1 to 30ω harmonics were calculated.…”