Insight into the Experimental Error in the Mapping of Electrical Properties with Electrostatic Force Microscopy

Abstract

Electrostatic force microscopy (EFM) is an emergent, powerful technique for nanoscale detection of electrical properties such as permittivity and charge distribution. However, the surface irregularity of samples has been unfortunately overlooked in most EFM studies. Herein, we use a polymer nanocomposite dielectric (PND) as the showcase and demonstrate that the morphological discontinuity at the matrix/particle interface can lead to major discrepancies or even incorrect results in the EFM study. First, the influence of the morphology, permittivity, and charge density of the interface is quantitively analyzed with a numerical method, proving that linking EFM results directly to sample properties is impracticable in the research based on classical interface configuration. Then, two methods are proposed to address the issue. The first method is numerical inversion, which takes heterogeneous materials and irregular surfaces into consideration. In this method, the influence of several experimental uncertainties, such as the radius of the nanoparticle and the permittivity of the matrix, is estimated. It is shown that the uncertainties related to geometry have a great impact on inversion and should be determined preferentially. In the second method, two standard configurations of the interface are recommended and compared for the interface study to bypass the morphological issue. This work provides quantitative results regarding the longoverlooked error in the EFM detection of the microregion with heterogeneous composition and surface irregularities and offers methods to tackle this issue.

Polymer Nanocomposite Dielectrics: Understanding the Matrix/Particle Interface

“…Recently, in the topic of interface detection by EFM, the influence of the morphology, polarization, and charge in the interfacial region on measurement was analyzed by FEM simulation (Figure f). Significant impact from the surface irregularities was confirmed­(Figure g,h), which is much greater than the impact from polarization and charge modification in the interface . Hence, it was suggested that the local interfacial polarization and charge detection based on SPM should be dealt with carefully, with more attention paid to the morphology of the sample and the uncertainty in the EFM, which has a major impact on the conclusions.…”

“…Significant impact from the surface irregularities was confirmed(Figure 13g,h), which is much greater than the impact from polarization and charge modification in the interface. 212 Hence, it was suggested that the local interfacial polarization and charge detection based on SPM should be dealt with carefully, with more attention paid to the morphology of the sample and the uncertainty in the EFM, which has a major impact on the conclusions. Besides the above-mentioned factors, SPM, a surface testing technique, has the inherent problem to peel off the surface effect.…”

“…(i) Relative permittivity ε i of 1.5–10 and (j) charge density ρ i of 0–10 4 C/m 3 plotted in different colors. Adapted with permission from ref . Copyright 2022 American Chemical Society.…”

Design and characterization of molecular, crystal and interfacial structures of PVDF-based dielectric nanocomposites for electric energy storage

“…Wang et al 172 reported that electrostatic force microscopy (EFM) is an innovative technique to detect the electric performance and charge distribution of the interface at nanoscale, as shown in Fig. 16(d) and (e).…”

“…171 (d) Potential of the system when the probe is above the particle, interface, and matrix. 172 (e) Calculated results of the electrical force and force gradient. 172 (f) Schematic diagram of charge/discharge by scanning probe microscopy, SPM topography and amplitude images of the cross-linked nanocomposite (N 2 C 15 ).…”