Formation of Au nanostructures on the surfaces of annealed [formula omitted] thin films

Abstract

One of the promising methods for high-throughput fabrication of nanostructures is the spontaneous dewetting of an as-deposited thin film. The formation process of Au nanostructures (AuNS) on TiO2 thin films consisted of two steps: formation of Au thin films and post-deposition annealing at 500∘C temperature in Ar gas environment for 60 minutes. TiO2 thin films were deposited using reactive magnetron sputtering method on SiO2 and fused quartz substrates and soaked at 500∘C and 900∘C temperatures to understand the influence of crystalline structure and surface morphology of Au and TiO2 thin films on the formation of AuNS. Properties of the deposited thin films were investigated using XRD, SEM, AFM, and RAMAN. The mean diameter (Dmean), mean area of AuNS (Amean), and mean distance between centroids of nearest neighbor AuNS (NNDcentr) increased exponentially when thicker nanocrystalline Au films were annealed. Standard deviation from Dmean and coefficient of variation also increased indicating higher dispersion of AuNS diameter. It was found that the influence of surface roughness increased by annealing thicker nanocrystalline Au thin films. Dmean, Amean, and NNDcentr increased and the density of AuNS (n) decreased (hAu: 10 nm and 15 nm) with decreasing Rq of TiO2 thin films. The peaks of absorbance (500 nm- 750 nm) were broad and not symmetrical indicating multiple localized surface plasmon resonance (LSPR) from various size AuNS. The position of peak shifted to the longer wavelengths when Dmean and NNDcentr was larger.