Room Temperature Epitaxy of Wafer-Scale Copper Films with High Electronic and Optical Performance

Copper (Cu) is an indispensable conductive material widely utilized in applications such as integrated electronic circuits and the growth of two-dimensional materials. Single-crystalline Cu exhibits superior performance over polycrystalline Cu; however, the synthesis of single-crystalline Cu typically requires relatively high temperatures. Therefore, the realization of room-temperature epitaxy for Cu films is crucial for advancing both fundamental science and practical applications. Here, we synthesized high-quality wafer-scale Cu films at room temperature by homemade high-pressure magnetron sputtering. The measurements of the crystal and electronic structures confirmed the high quality of the films. Atomic force microscopy characterized a smooth and uniform surface of the films. Remarkably, the unexpectedly high carrier density (10²³ cm^–3) and exceptional optical properties of the Cu films were revealed through electrical transport and spectroscopic ellipsometry measurements, comparable to those of bulk crystals. Our results demonstrate the successful achievement of high-quality single-crystalline Cu films grown at room temperature, offering significant potential for integrating the films into advanced electronic, photonic, and flexible applications.