First-Principles TDDFT–MD Investigation of Charge Trapping Mechanisms in Amorphous HNSi

Amorphous silicon nitride is a promising candidate for charge-trapping layers in next-generation nonvolatile memory devices. However, the microscopic mechanism governing charge trapping remains elusive. Recent first-principles studies suggest that local bond reorganization plays a key role in this process. To further examine this hypothesis, we investigate the dynamical evolution of charge trapping using nonadiabatic TDDFT–MD, an effective approach for probing the interplay between electronic excitations and atomic motion.

An amorphous hydrogen–nitrogen–silicon (HNSi) network containing four coordination defects was generated via a melt–quench procedure, in which hydrogen atoms were introduced to passivate potential dangling bonds during amorphization. Upon electron injection, the HNSi system underwent a sequence of structural rearrangements involving transformations of coordination defects and correlated charge redistributions. These time-dependent processes reveal how injected carriers interact with the amorphous network to form stable trap states. This study provides atomistic insight into the coupling between defect dynamics and charge localization, offering a mechanistic basis for charge retention and guiding the design of reliable nonvolatile memory materials.