Ultra-high conductive copper with micron-grain and nano-twin microstructures prepared by electrodeposition

The record-breaking ultra-conductive copper films with characterized microstructures of micron-sized grains and nano-twins (mGnT-Cu) were synthesized using a direct current electrodeposition method in this work. By optimizing pH, current density, and deposition time, the mGnT-Cu achieved the highest electrical conductivity of 103.8±0.8% IACS through four-probe measurement (111.7±1.49% IACS measured by eddy current method), which significantly surpassed other reported polycrystalline coppers, including oxygen-free copper (100.5% IACS) and nano-twin copper (96.9% IACS). Notably, the mGnT-Cu’s electronic conductivity is only 1.3% lower than that of single-crystal copper (SCC) with 105.2% IACS. However, its tensile strength of 283.8 MPa is 2.2 times higher than that of SCC (128.5 MPa). The electron backscattering diffraction and transmission electron microscopy revealed that the sample with the highest conductivity contained 48.2% twin layers with an average thickness of 55 nm and a grain size of 1.12 μm, compared to the reported nano-twin copper with twin layer thickness of 27 nm and a grain size of 400 nm. The larger grain size and twin layer thickness of mGnT-Cu films are responsible for their ultra-high conductivity. This cost-effective electrodeposition method enables the large-scale production of ultra-high electroconductive Cu films for applications in electronics, transportation, and aerospace industries.