Inverse Stranski–Krastanov Growth in Single-Crystalline Sputtered Cu Thin Films for Wafer-Scale Device Applications

The single-crystalline copper (Cu) thin film is a platform substrate for the growth of numerous materials and has been a significant issue for the scientific community. The primary concern is the inevitable presence of stacking faults and twin boundary formation in inherent face-centered-cubic (FCC) structures. Here, we report a method for growing single-crystalline Cu(111) thin films on an Al₂O₃ substrate using conventional sputtering deposition. The desired growth configuration is induced by hidden incoherent twin boundaries (HITBs) embedded during the early growth stages. Two possible FCC stacking orders of Cu atoms, A-B-C-A and A-C-B-A rotated by 60°, give rise to HITBs between islands, as confirmed by X-ray diffraction phi-scan mapping. Such islands merge every three layers, triggering layer-by-layer growth that subsequently leads to an inverse Stranski–Krastanov growth mode. Single-crystalline Cu(111) thin film growth is confirmed by high-resolution transmission electron microscopy and electron backscatter diffraction mapping. Our approach paves the way for mass production of single-crystalline metal thin film and thus leads to substantial advanced research and electronic device application.