Hidden Stacking Fault Charge Traps in Hexagonal Boron Nitride and Their Impact on Dielectric Breakdown.

Understanding structural disorder is central to material science and nanotechnology. Even though van der Waals (vdW) assembly techniques allow one to design heterostructures on demand, structural deformation and disorder remain inevitable, degrading vdW device performance and reproducibility. Here, we show that mechanical manipulation generates invisible stacking fault ribbons in hexagonal boron nitride (hBN) multilayers that bind excitons, trap charges, and locally weaken dielectric strength. Correlated scanning electron microscopy and cathodoluminescence (SEM-CL) maps reveal linear defects with near-band-edge emissions attributed to stacking fault-bound excitons. Dose-dependent SEM and CL independently show robust charge trapping behavior at stacking fault ribbons with persistent secondary electron (SE) contrast and saturable CL emission. Lateral force microscopy resolves the stacking fault ribbons, enabling local breakdown measurements, which reveal reduced breakdown voltages along the ribbons from trap-defined localized failure paths. Our multimodal approach can be generalized to other layered materials to map electronically and dielectrically active structural disorders, improving understanding and controllability of vdW devices.