Replenish and relax: explaining logarithmic annealing in disordered materials

TL;DR

This paper investigates the microscopic mechanisms behind logarithmic structural relaxation in disordered materials, using experiments and simulations on ion-damaged silicon to reveal a replenish and relax process that explains long-term aging.

Contribution

It introduces a combined experimental and simulation approach to elucidate the atomistic origin of logarithmic relaxation in disordered materials, highlighting a two-step replenish and relax mechanism.

Findings

Logarithmic relaxation correlates with heat-release measurements.

A two-step replenish and relax process explains the relaxation.

Deeper energy states with growing barriers are involved in relaxation.

Abstract

Fatigue and aging of materials are, in large part, determined by the evolution of the atomic-scale structure in response to strains and perturbations. This coupling between microscopic structure and long time scales remains one of the main challenges in materials study. Focusing on a model system, ion-damaged crystalline silicon, we combine nanocalorimetric experiments with an off-lattice kinetic Monte Carlo simulation to identify the atomistic mechanisms responsible for the structural relaxation over long time scales. We relate the logarithmic relaxation, observed in a number of systems, with heat-release measurements. The microscopic mechanism associated with logarithmic relaxation can be described as a two-step replenish and relax process. As the system relaxes, it reaches deeper energy states with logarithmically growing barriers that need to be unlocked to replenish the heat-releasing events leading to lower energy configurations.