Highly impermeable and transparent graphene as an ultra-thin protection barrier for Ag thin films

Ag thin films have a wide variety of applications in optics. However, Ag is chemically unstable under atmospheric conditions, which significantly degrades its optical properties and hinders its practical applications. Conventional protective coatings retard or inhibit the corrosion of Ag, but also alter the optical properties of Ag substantially. In this work, we transfer highly impermeable and transparent monolayer graphene onto the surface of Ag thin films as an ultra-thin protection barrier. We comparatively study the morphological and spectroscopic characteristics of the Ag thin films with and without the graphene protective barrier, revealing the high corrosion-resistance of monolayer graphene to gases and liquids. The Tafel analysis shows that the corrosion rate of the Ag thin film is reduced by about 66 times by the use of a graphene protection barrier. We further demonstrate that the graphene coated Ag thin films can be used for optical applications, including optical mirrors and surface enhanced Raman spectroscopy substrates. Our results show that monolayer graphene as a protective barrier simultaneously maintains the high stability and unique optical properties of Ag thin films.