Atomic Scale Understanding of Cu and Cu Alloy Oxidation Using In Situ Environmental TEM

How metals and alloys oxidize is of critical importance to numerous energy, environmental, and microelectronics industries. A fundamental understanding of the surface oxidation of metals and alloys are essential for improving existing processes and designing new functional materials that use oxidation for nanomaterials formation. Experimental tools capable of observing in situ the early-stage oxidation at the atomic scale are key to predictive oxidation. Here, we use in situ environmental transmission electron microscopy (ETEM) experiments, with advanced data analysis and correlated theoretical simulations, to investigate the initial stages of Cu and CuNi oxidation. Single-crystalline ~60 nm Cu and CuNi thin films were prepared by ebeam evaporation and then transferred to a dedicated ETEM with a home-built gas delivery system. The onset of surface reconstruction, nucleation and initial growth of the epitaxial oxides are followed in situ. In-depth analysis of these atomic scale processes is completed via automated ETEM data-processing and statistical techniques. For gaining fundamental understandings, a multiscale theoretical framework is being developed for simulating longer time scales to correlate directly with experimental observations. Mechanistic understanding of the role of surfaces, defects and composition is obtained. The authors acknowledge funding from National Science Foundation (NSF) grants DMR-1410055, DMR-1508417, DMR-1410335, and CMMI-1905647, as well as support from Hitachi-High-Tech and technical assistance from the Nanoscale Fabrication and Characterization Facility (NFCF) in the Petersen Institute of Nano Science and Engineering (PINSE) at the University of Pittsburgh. This research used the Electron Microscopy resources of the Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science User Facility, at Brookhaven National Laboratory under Contract No. DESC0012704.