Microstructural evolution of Au/TiO2 nanocomposite films: The influence of Au concentration and thermal annealing

Abstract

Nanocomposite thin films consisting of a dielectric matrix, such as titanium oxide (TiO 2 ), with embedded gold (Au) nanoparticles were prepared and will be analysed and discussed in detail in the present work. The evolution of morphological and structural features was studied for a wide range of Au concentrations and for annealing treatments in air, for temperatures ranging from 200 to 800 ºC. Major findings revealed that for low Au atomic concentrations (at. %), there are only traces of clustering, and just for relatively high annealing temperatures, T ≥ 500 ºC. Furthermore, the number of Au nanoparticles is extremely low, even for the highest annealing temperature, T = 800 ºC.It is noteworthy that the TiO 2 matrix also crystallizes in the anatase phase for annealing temperatures above 300 ºC.

Thin films composed of Ag nanoclusters dispersed in TiO2: Influence of composition and thermal annealing on the microstructure and physical responses

“…Anyway, the results displayed in Fig. 1 show that the Ag placed at the target surface was not enough to significantly disturb the discharge characteristics, similarly to what was reported for the Au:TiO 2 system [14]. This is a consequence of the low fraction of silver used to produce the films, always less than 1 % of the total area of the Ti target.…”

“…The working pressure (about 4.5×10 -1 Pa) was constant during the deposition of the film. The oxygen partial pressure was chosen according to the hysteresis experiment, which is described in [14]. Moreover, the conditions described above are similar to those used to produce the Au:TiO 2 system [14], where the Au pellets are here "replaced" by Ag.…”

“…In order to study some of those deposition-related features, the evolution of the target to the chamber with a partial pressure that ensures the "poisoning" of the target surface with a superficial oxide layer (compound regime of the target), as already discussed elsewhere [14].…”

“…The overall set of results showed that the growth of Au nanoparticles/clusters with different sizes and size distributions is highly dependent of the annealing temperature [14] and, on the other hand, the intermediate Au contents, i.e. between 5 at.% and 15at.%, can produce a spectrally broad LSPR bands [16] [17].…”

“…In recent works it was studied the influence of gold concentration, dispersed in a TiO 2 matrix, and annealing temperature on the microstructural features and optical response of Au:TiO 2 thin films [12] [13] [14] [15]. The overall set of results showed that the growth of Au nanoparticles/clusters with different sizes and size distributions is highly dependent of the annealing temperature [14] and, on the other hand, the intermediate Au contents, i.e.…”