Effects of Al-doping concentration on the structure and electromagnetic shielding properties of transparent Ag thin films

Abstract

The ultra-thin Ag films with fascinating optical properties and shielding performance have broad applications in the fields of solar cells, transparent electrodes, optical spectrum filters, low-emissivity coatings, transparent electromagnetic shielding windows, etc. In this work, by introducing Al dopant, ultra-thin Ag transparent films were successfully prepared on quartz glass substrates using magnetron co-sputtering method. Effects of the Al-doping concentration on the structure, transmittance and electromagnetic shielding properties of Ag thin films were investigated in detail. It was found that a certain amount of Al can suppress the 3D island growth of Ag granules, and thus promote nucleation and continuous in plane growth. At the Al doped concentration of 5 mol%, the prepared 9 nm Al doped Ag thin films exhibited continuous, uniform and smooth surface morphology with the RMS roughness of only 0.89 nm. Meanwhile, it has good optical property with the highest transmittance value of 80.2% in the visible range and 76.8% at 550 nm. As the increase of Al concentration, the shielding effectiveness of the films goes up and then down, and the optimum concentration for maximum shielding effectiveness (SE) is about 5 mol% at which the maximum SE can reach up to 34.5 dB. These features make the Al-doped Ag thin films very useful and practical for transparent electromagnetic shielding window.