Single-crystalline silver film grown on Si (100) substrate by using electron-gun evaporation and thermal treatment

The authors demonstrate a simple method to fabricate ultrasmooth single-crystalline silver (Ag) films with high reflectivity and low plasmonic damping. The single-crystalline Ag thin film on the clean Si (100) substrate is first deposited by electron-gun evaporator and then treated by rapid thermal annealing (RTA) to improve its quality. The crystal structure and surface morphology are characterized by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Optical constants of the prepared films are extracted by fitting the measured reflectivity spectra with the Drude model. These results show that the Ag film with 340 °C RTA has the best film quality, including small surface roughness of 0.46 nm, a sharp x-ray diffraction peak with FWHM of 0.3°, and lowest damping in the visible and near-infrared wavelength regime. Therefore, our method is not only cost-effective but also useful for fabricating metal-based plasmonic and nanophotonic devices.