Strategy for Fabricating Ultrathin Au Film Electrodes with Ultralow Optoelectrical Losses and High Stability

A vital objective in the wetting of Au deposited on chemically heterogeneous oxides is to synthesize a completely continuous, highly crystalline, ultrathin-layered geometry with minimized electrical and optical losses. However, no effective solution has been proposed for synthesizing an ideal Au-layered structure. This study presents evidence for the effectiveness of atomic oxygen-mediated growth of such an ideal Au layer by improving Au wetting on ZnO substrates with a substantial reduction in free energy. The unexpected outcome of the atomic oxygen-mediated Au growth can be attributed to the unconventional segregation and incorporation of atomic oxygen along the outermost boundaries of Au nanostructures evolving in the clustering and layering stages. Moreover, the experimental and numerical investigations revealed the spontaneous migration of atomic oxygen from an interstitial oxygen surplus ZnO bulk to the Au-ZnO interface, as well as the segregation (float-out) of the atomic oxygen toward the top Au surfaces. Thus, the implementation of a 4-nm-thick, two-dimensional, quasi-single-crystalline Au layer with a nearly complete crystalline realignment at a mild temperature (570 K) enabled exceptional optoelectrical performance with record-low resistivity (<7.5 × 10^-8 Ω·m) and minimal optical loss (∼3.5%) at a wavelength of 700 nm.