Dielectrics are central to microelectronics, where their field-driven polarization governs energy storage and device performance, making direct nanoscale access to their internal electrical response under operating bias critical for further optimization. Here, we investigate the local charge accumulation associated with leakage current in a p-doped Si/SiN/Ti nanocapacitor under controlled bias conditions. By combining operando electron holography with finite-element modeling, we quantitatively map electrostatic potentials and space-charge distributions. We reveal a reversible volume charge density within the dielectric whose sign switches with bias polarity, leading to a redistribution of the interfacial charges. Identifying Schottky emission as the dominant conduction mechanism, we attribute the observed space-charge accumulation to the asymmetric injection between the electrode/dielectric interfaces and evaluate its impact on the effective differential capacitance. These findings establish a robust operando framework based on electron holography for probing nanoscale electrical properties and disentangling competing leakage mechanisms in advanced micro- and nanoscale capacitors.
Disic et al. (2026) studied this question.