Evolution of the surface plasmon resonance of Au:TiO2 nanocomposite thin films with annealing temperature

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology Vol. 16; no. 12; p. 1
• Main Authors: Borges, J., Buljan, M., Sancho-Parramon, J., Bogdanovic-Radovic, I., Siketic, Z., Scherer, T., Kübel, C., Bernstorff, S., Cavaleiro, A., Vaz, F., Rolo, A. G.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-12-2014; Springer; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystallization; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Gold; Inorganic Chemistry; Lasers; Materials Science; Nanocrystalline materials; Nanoparticles; Nanoscale materials and structures: fabrication and characterization; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Nanotechnology; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Research Paper; Resonance; Specific phase transitions; Structural transitions in nanoscale materials; Structure of solids and liquids; crystallography; Thin films; Titanium dioxide; Wavelengths; Thin films; Dielectric function; Nanocomposites; Au nanoparticles; TiO; matrix; Localized surface plasmon resonance; Red shift; Morphological changes; Annealing temperature; Nanoparticles; Temperature effects; Size effect; Thermal annealing; Crystal structure; Grain size; Temperature dependence; Gold; Vacuum annealing; Phase transformations; Crystallization; Spectral line shift; Growth mechanism; Crystal-phase transformations; Surface plasmon resonance; Optical sensors; Nanostructured materials
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-014-2790-7

This paper reports on the changes in the structural and morphological features occurring in a particular type of nanocomposite thin-film system, composed of Au nanoparticles (NPs) dispersed in a host TiO
2
dielectric matrix. The structural and morphological changes, promoted by in-vacuum annealing experiments of the as-deposited thin films at different temperatures (ranging from 200 to 800 °C), resulted in a well-known localized surface plasmon resonance (LSPR) phenomenon, which gave rise to a set of different optical responses that can be tailored for a wide number of applications, including those for optical-based sensors. The results show that the annealing experiments enabled a gradual increase of the mean grain size of the Au NPs (from 2 to 23 nm), and changes in their distributions and separations within the dielectric matrix. For higher annealing temperatures of the as-deposited films, a broad size distribution of Au NPs was found (sizes up to 100 nm). The structural conditions necessary to produce LSPR activity were found to occur for annealing experiments above 300 °C, which corresponded to the crystallization of the gold NPs, with an average size strongly dependent on the annealing temperature itself. The main factor for the promotion of LSPR was the growth of gold NPs and their redistribution throughout the host matrix. On the other hand, the host matrix started to crystallize at an annealing temperature of about 500 °C, which is an important parameter to explain the shift of the LSPR peak position to longer wavelengths, i.e. a red-shift.