Alfredo Tolley

Formation of epitaxial β-Sn islands at the interface of SiO2∕Si layers implanted with Sn ions

180 nm SiO2 layers on Si (100) were implanted with Sn ions producing a profile with a peak concentration of 3 at. % at the middle of the oxide. After high temperature (900–1100 °C) annealing, an array of β-Sn islands epitaxially attached to the Si was observed at the SiO2∕Si(100) interface due to the migration of the implanted Sn atoms. The breakdown of the planar SiO2∕Si interface and the appearance of the island system is discussed in terms of the Sn–Si equilibrium properties. Our results reveal a new method to create a high density of nanosized islands with good uniformity in size and shape.

The spontaneous room temperature reduction of HAuCl4 in ethylene glycol in the presence of ZnO: a simple strategy to obtain stable Au/ZnO nanostructures exhibiting strong surface plasmon resonance and efficient electron storage properties

The room temperature spontaneous reduction of HAuCl4 in ethylene glycol in the presence of pre-formed ZnO nanoparticles is investigated by UV-vis spectroscopy. Analysis by HRTEM demonstrated that the synthesized nanostructures consist of small ZnO nanoparticles (5.0 nm) in contact with bigger (15 nm) spherical Au nanoparticles. The electronic communication between Au and ZnO blocks is confirmed by UV excitation of the colloid. These experiments indicate that ZnO nanoparticles efficiently transfer the electrons to Au nanoparticles in contact, inducing a 15 nm blue shift in the plasmon band. Titration experiments using the methylviologen couple (MV2+/MV˙+) are presented and analyzed to quantify the enhancement in the electron storage capability in the new nanostructure and the negative shift in the Fermi level caused by the Au loading in ZnO.