2026-04-14 カリフォルニア大学サンタバーバラ校（UCSB）
Photo Credit:Illustration by Woncheol Lee
A concept illustration depicting a single “hot electron” causing a hydrogen-silicon bond to break, degrading performance
＜関連情報＞
- https://news.ucsb.edu/2026/022508/new-model-explains-how-single-electrons-cause-damage-inside-silicon-chips
- https://journals.aps.org/prb/abstract/10.1103/3ync-nxm8
固体システムにおける共鳴状態と核ダイナミクス：シリコン-水素結合解離の事例 Resonant states and nuclear dynamics in solid-state systems: The case of silicon-hydrogen bond dissociation
Woncheol Lee, Mark E. Turiansky, Dominic Waldhör, Byounghak Lee, Tibor Grasser, and Chris G. Van de Walle
Physical Review B Published: 11 February, 2026
DOI: https://doi.org/10.1103/3ync-nxm8
Abstract
Bond breaking in the presence of highly energetic carriers is central to many important phenomena in physics and chemistry, including radiation damage, hot-carrier degradation, activation of dopant-hydrogen complexes in semiconductors, and photocatalysis. Describing these processes from first principles has remained an elusive goal. Here we introduce a comprehensive theoretical framework for the dissociation process, emphasizing the need for a nonadiabatic approach. We develop the methodology and benchmark the results for the case of silicon-hydrogen bond dissocation, a primary process for hot-carrier degradation. Passivation of Si dangling bonds by hydrogen is vital in all Si devices because it eliminates electrically active mid-gap states; understanding the mechanism for dissociation of these bonds is therefore crucial for device technology. While the need for a nonadiabatic approach has been previously recognized, explicitly obtaining diabatic states for solid-state systems has been an outstanding challenge. We demonstrate how to obtain these states by applying a partitioning scheme to the Hamiltonian obtained from first-principles density functional theory. This approach enables us to identify the Si-H bonding (δ) and antibonding (δ*) states, from which we extract their energy eigenvalues and map the associated potential-energy surfaces. Our results demonstrate that bond dissociation can occur when electrons temporarily occupy the antibonding states, generating a highly repulsive excited-state potential that causes the hydrogen nuclear wave packet to shift and propagate rapidly. Based on the Menzel-Gomer-Redhead (MGR) model, we show that after moving on this excited-state potential on femtosecond timescales, a portion of the nuclear wave packet can continue to propagate even after the system relaxes back to the ground state, allowing us to determine the dissociation probability. By averaging over quantum trajectories, we calculate a quantum yield that directly aligns with experimentally measured desorption yields. Our model effectively explains key experimental features—such as the 7 V threshold bias for dissociation, as well as the presence of a finite dissociation probability even at lower bias ranges, the high isotope ratio between the desorption yields of hydrogen and deuterium, and the temperature independence of the dissociation process—observed in scanning tunneling microscopy (STM) and low-energy electron injection experiments. Finally, we apply our approach to a representative device scenario, demonstrating its capability to explain the degradation observed in oxide-stress experiments. Our results provide essential insights into the fundamental processes that drive carrier-induced bond breaking in general, and specifically elucidate hydrogen-related degradation in Si devices, with potential implications for improving device reliability and performance.
