Simultaneous Interface Defect Density and Differential Capacitance Imaging by Time-Resolved Scanning Nonlinear Dielectric Microscopy

This work highlights the unique capabilities of time-resolved scanning nonlinear dielectric microscopy as demonstrated in the study of SiO₂/SiC interfaces. Scanning nonlinear dielectric microscopy (SNDM) is a microwave-based scanning probe technique with high sensitivity to variations in tip-sample capacitance. Time-resolved SNDM, a modified version, is used in this study because it allows simultaneous nanoscale imaging of interface defect density (D_it) and differential capacitance (dC/dV), lending itself to correlation analysis and a better understanding of the relationships that influence interface quality. Through cross-correlation analysis, it is shown that D_it images are not strongly correlated with simultaneously obtained dC/dV images, but rather with difference images derived from dC/dV images recorded with different voltage sweep directions. The results indicate that the dC/dV images visualize the nonuniformity of the total interface charge density and the difference images reflect that of D_it at a particular energy range.