A New Method for Studying He Damage in Materials Demonstrated on Nanotwinned Cu Nanopillars

Abstract

Ion implantation has been used for decades to investigate the response of materials to radiation damage. While displacement damage is caused due to an incoming particle, in high neutron energy environments gases are also produced due to transmutation or fission events. In particular fusion, fast reactor and spallation sources suffer from high He/dpa (displacements per atom) ratios. Understanding the effect of He in materials is a key aspect in these applications. It is known that interfaces are beneficial for radiation damage due to the fact that interfaces act as defect sinks. In the past He-denuded zones around grain boundaries have often been observed which prove that He can be managed by offering defect sinks [1]. Only a few studies have been performed investigating the effect of twin interfaces on He management [2]. The studies performed are rather limited in exploring different doses due to the fact that implanting the same grain with different doses and subsequent characterization of the resulting defects are challenging and rather time consuming, thus limiting systematic studies. Moreover, in order to obtain a direct comparison ideally one implants the same sample and same grain to different doses. Recently the Zeiss ORION NanoFab instrument was released which allows He and Ne ion beams in combination with a Ga ion source to quickly and efficiently manufacture nanostructures and direct He implantation [3]. In this work we utilize the combined Ga-He beam system to increase sample throughput and manufacture nanopillars with subsequent He implantation in a fast and efficient manner. Using this novel method one can manufacture nanopillars and implant these targeting the exact same grain in one session, thereby allowing for better and more accurate comparison and effect evaluation due to better controlled separate effect testing.