Fast Engineering Models for Radiation-Induced Defect Production in Thin Materials

Due to the rapid evolution of electronic devices based on advanced lithography techniques and the commercialization of space, methods are needed to assess and predict performance in adverse radiation environments of both the transient and long-term response to irradiation. Experimental measurements of radiation damage generally exist on the order of hours after irradiation, and simulations are able to provide detailed predictions of damage out to the order of picoseconds. Additionally, radiation damage and interactions at depths below the mean free path of radiation in a particular material have long proven difficult quantities to measure and challenging to predict. A potential method is explored for predicting the concentration of defects in a material resulting from neutron irradiation, and the method's output is compared against experimental results for the well-studied material, MgO. The Monte Carlo Neutral Particle transport code (MCNP), leveraging the PTRAC module, is used to simulate irradiation of MgO samples with dimensions that are sub-mean free path, in the Oak Ridge National Laboratory’s High Flux Isotope Reactor (HFIR). Cluster dynamics results and atomic displacement theory are used to compute the total number of defects in transient phase and account for the effects of defect saturation and thermal annealing. Comparison of the long-term response is then compared against actual experimental results of MgO irradiation in the HFIR and shown to agree within a factor of two. The method is then broadened to examine the spatial distribution of defects in the sample. Other materials are also explored for comparison including Si and GaN.