Transferable ultrasmooth gold films prepared <i>via</i> the masking method

Gold thin films play a vital role in a wide range of applications due to their outstanding electrical conductivity, chemical stability, and unique optical properties. They are indispensable in electronic and optoelectronic devices where achieving low contact resistance and high durability is critical. In this study, a technique for fabricating transferable ultrasmooth gold thin films is introduced, in which graphite is used as a mask. Ultrasmooth areas up to 400 μm² are created-two orders of magnitude larger than those achieved by previous techniques. A surface roughness of <i>R</i>_a 0.05 nm and a maximum peak height of 0.20 nm are achieved, representing the lowest values reported to date. Consequently, when forming contact with a graphite flake of 6 μm in size, the actual contact area and conductance are increased by 5 times. By sliding against a SiO₂ microsphere covered with diamond-like carbon (DLC), the friction force is decreased by 50%, and the maximum wear scar depth is reduced by an order of magnitude under a contact stress of 310 MPa. This method is straightforward to execute, cost-effective, and versatile, making it suitable for the fabrication of a wide range of metal films in electrical, tribological, and optical applications.