Patterning of plasmonic Au nanoparticles on the surfaces of TiOx thin films by solid state thermal dewetting

It is essential to study the thermal dewetting behavior of as-deposited nano-films for large scale and high-throughput fabrication. We report here on the nucleation of Au nanostructures onto titanium dioxide (TiOx) thin films surfaces, which occurred in consecutive steps. First, TiOx thin films were grown on quartz substrates reactively by e-beam evaporator and then thermally annealed at different temperatures, starting from 300 degrees C to 900 degrees C. Subsequently, a nano-film of Au was deposited on the top of these TiOx surfaces. The stacked Au/TiOx samples were post-annealed using muffle furnace at a temperature of 600 degrees C for 1 h, to study the thermal dewetting properties and the controlled growth of the different TiOx morphologies on the formation of Au nanoparticles (NP) and their plasmonic response. Such dual-structures were characterized accordingly to probe their topological, morphological, structural, and optical properties, by means of x-ray photoelectron spectroscopy, scanning electron microscope, atomic force microscopy, and ultra-violet-visible-near infrared characterization techniques. The thermal dewetting properties were found to improve at high temperatures (>500 degrees C), where the Au NP size distribution was found to follow a Gaussian pattern centered around 30 nm. The average surface roughness also increased significantly with respect to the TiOx dewetting temperature, which is mainly attributed to the porosity of the films. Finally, the absorption peak for Au nanostructures has shown a localized surface plasmon resonance close to 520 nm, along with a broad shoulder peak with a strong tail thereby reflecting the wide distribution of the formed Au NP sizes. (c) 2023 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.JPE.13.025501]