Dielectric Breakdown Mechanisms in High-κ Antimony Trioxide (Sb₂O₃)

High-κ gate dielectrics compatible with two-dimensional (2D) materials are crucial for advanced electronics, and Sb2O3 (antimony trioxide) shows significant potential. Here, we show that the soft breakdown induces oxygen vacancies and migration of copper into Sb2O3. Hard breakdown, driven by joule heating, gives rise to a substantial temperature increase, leading to morphological transformations and oxygen redistribution. In situ transmission electron microscopy (in situ TEM) measurements correlated with device performance show the formation of nanoconducting filaments due to the increased concentration of oxygen vacancies and copper migration in connection with the soft breakdown. The hard breakdown is associated with the formation of antimony-enriched nanocrystals. These findings offer critical insights into the suitability of Sb2O3 as a high-κ gate dielectric.