Implantation, Characterization, and Formation Mechanisms of Gold Nanocrystals in TiO2 Thin Film and Nanowires

Abstract

Gold (Au) nanocrystals were thermally evaporated and implanted into a film by a two-step vacuum process. In the experiment, two different specimens, as-prepared sample substrate and source material Ti powder were combined. In the first stage, the materials underwent thermal evaporation (at for the first material and at for the second material) under a vacuum pressure of for . In the second step, the vacuum system was fed with air and maintained at for . The air pressure implanted the Au nanoclusters into the film. The process also synthesized nanowires. High-angle annular dark-field imaging by a scanning transmission electron microscope (HAADF/STEM) revealed that the Au nanocrystals (nanoclusters) were highly dispersed in the film and its nanowires. The diameters of the nanowires ranged from , and their lengths were up to . High-resolution transmission electron microscopy with energy dispersive X-ray spectroscopy mapping, HAADF/STEM, X-ray photoelectron spectroscopy, and X-ray diffractometry were used to elucidate the formation process of the as-synthesized products. The results indicated that as-synthesized nanowires had been formed by a combination of solid-liquid-solid and vapor-solid mechanisms.