Plasmonic behaviour of sputtered Au nanoisland arrays

Abstract

The specificity of the formation of Au sputtered nanoisland arrays (NIA) on a glass substrate or on a ZnO thin film doped by Ga is demonstrated. Statistical analysis of morphology images (SEM, AFM) exhibited the Log-normal distribution of the size (area) of nanoislands—their modus AM varied from 8 to 328nm2 depending on the sputtering power density, which determined the nominal thicknesses in the range of 2–8nm. Preferential polycrystalline texture (111) of Au NIA increased with the power density and after annealing. Transverse localised surface plasmonic resonance (LSPR; evaluated by transmission UV–vis spectroscopy) showed the red shift of the extinction peaks (Δl≤100nm) with an increase of the nominal thickness, and the blue shift (Δλ≤−65nm) after annealing of Au NIA. The plasmonic behaviour of Au NIA was described by modification of a size-scaling universal model using the nominal thin film thickness as a technological scaling parameter. Sputtering of a Ti intermediate adhesive ultrathin film between the glass substrate and gold improves the adhesion of Au nanoislands as well as supporting the formation of more defined Au NIA structures of smaller dimensions.