Showing papers by "Anabela G. Rolo published in 2014"
TL;DR: In this paper, the structural and morphological changes occurring in a particular type of nanocomposite thin-film system, composed of Au nanoparticles (NPs) dispersed in a host TiO2 dielectric matrix, were investigated.
Abstract: 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 TiO2 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.
27 citations
15 Jul 2014-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, an ion beam analysis study with the Rutherford backscattering and elastic recoil analysis detection techniques was performed to determine the thickness and composition of the nanolayers, and gain insight into the evolution of the roughness of the layers.
Abstract: SiGe/SiO2 multilayers with layer thickness of 5 nm were deposited with RF magnetron sputtering. The as deposited samples had well defined SiGe amorphous layers. Different annealing treatments were made to promote the formation of SiGe nanocrystals. We report an ion beam analysis study with the Rutherford backscattering and elastic recoil analysis detection techniques, in order to determine the thickness and composition of the nanolayers, and gain insight into the evolution of the roughness of the layers. The results are correlated with other structural properties of the samples, as measured with complementary techniques such as grazing incidence X-ray diffraction annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy.
3 citations