Unravelling Nanometallurgy with in Situ Electron-Microscopy: A Case Study with Cu Nanowires

Technological advances set new challenges for materials development. Minia-rtheless, by studying the Cu at the nanoscale, someTechnological advances set new challenges for materials development. Miniaturization of electronic devices demands the migration of metallurgy from macro/micro to the nanoscale, thus requiring a re-definition of existing and classical concepts in metallurgy. The present study reports on the behaviour of pure Cu nanowires with diameters ranging from 40 to 140 nm heated in a low-pressure environment within a transmission electron microscope. The response of Cu nanowires was investigated at different temperatures up to 1123 K and analyzed using electron-microscopy techniques, revealing both volumetric and shape changes over time. Sublimation, with a steady-state length reduction of the nanowires, was identified as the dominant mechanism. Additionally, it was detected that sublimation occurred not only at temperatures above ~ 1023 K, where Cu has a higher vapor pressure than the column pressure of the electron-microscope, but also at temperatures as low as 923 K. This unexpected behavior is explained by the presence of active regions at sharply curved regions at the nanowire tip and the imbalance of evaporation and redeposition rates of Cu atoms due to the experimentally-induced loss of vapor atoms. Nevertheless, by studying the Cu at the nanoscale, some fundamental aspects of the field of nanometallurgy are unraveled.