Development of nano-porous Au thin film at room temperature via ion irradiation in a-Ge/Au bilayer system followed by chemical etching of Ge

The development of nano-porous gold (NPG) via room temperature ion irradiation has been presented in detail. The bilayer thin films of a-Ge/c-Au have been irradiated by 100 MeV Ni ions with the fluence of 5 × 10¹³ ions cm⁻² at room temperature. NPG is obtained by selectively etching Ge off from the Au matrix by dipping the Ge/Au thin film into 10 % H₂O₂ solution. Diffusion of Ge and Au across the interface under irradiation was confirmed by TRIM simulation and RBS spectra. The SEM image and EDX spectra confirms the formation of NPG with high purity. In addition, the statistical and fractal analysis of AFM image also confirms the formation of NPG. NPG system has been observed to show very good optical properties (low reflectance and high transmittance). The high quality NPG prepared by this method can be useful in the fields like optical sensors, transparent conductive electrodes, anti-reflective coatings, and photo-detector technology.