Nanostructured metal surfaces have been known to exhibit properties that deviate from that of the bulk material. By simply modifying the texture of a metal surface, various unique optical properties can be observed. In this paper, we present a simple two step electrochemical process combining electrodeposition and anodization to generate black gold surfaces. This process is simple, versatile and up-scalable for the production of large surfaces. The black gold films have remarkable optical behavior as they absorb more than 93% of incident light over the entire visible spectrum and also exhibit no specular reflectance. A careful analysis by scanning electron microscopy reveals that these unique optical properties are due to their randomly rough surface, as they consist in a forest of dendritic microstructures with a nanoscale roughness. This new type of black films can be fabricated to a large variety of substrates, turning them to super absorbers with potential applications in photovoltaic solar cells or highly sensitive detectors and so on.
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