Ce, Eu incorporation through doping of ALD-ZnO thin films for enhancing their photoluminescent properties.

Nanostructured ZnO nanoarrays deposited on silicon oriented substrates is a very promising area in the study of the control of physicochemical properties, in which photoluminescence plays a crucial role. This optical property inherent to ZnO, can be favorably modified through the inclusion of doping elements, with the purpose of appropriately modifying their optical absorption and luminescence. Following this objective, in the present work we present the development of Zn(1-x-y)Ce(x)Eu(y)O nanostructured thin films. The samples were produced in two steps process by atomic layer deposition technique followed by a solvothermal synthesis. The purpose of Cerium and Europium incorporation into the ZnO compound is to enhance the photoluminescence in ZnO thin films. In a first stage textured thin films were obtained from diethylzinc at a temperature of 190 °C and a pressure of 3.29 × 10-4 atm, on silicon substrates (111). Subsequently, the perpendicular growth of nanostructures was induced under a solvothermal process, where Zn(NO3)2 was used as Zn precursor and hexamethylene-tetramine operating as a dual-ligand to promote the linking of Zn2+ ions. The growth of cerium-europium ZnO nanostructures was promoted with Ce(C2H3O2)3·H2O and Eu(NO3)3·5H2O. The obtained Zn(1-x-y)Ce(x)Eu(y)O nanostructured thin films, were examined through SEM-microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and photoluminescence studies. The attained results show that it is feasible to produce Ce-Eu-doped ZnO nanostructures with tailored photoluminescence and crystal size. Interestingly the Ce-Eu doping induces a strong shift in comparison to the typical UV emission of ZnO; an effect that can be related with the increase of lattice defects in ZnO.

Enhanced nonreciprocal effects in magnetoplasmonic systems supporting simultaneously localized and propagating plasmons.

Perforated magnetoplasmonic Au/Co/Au multilayers support both localized and propagating surface plasmon resonances. The presence of holes produces an enhancement of the magnetic field modulation of the propagating surface plasmon wavevector with respect to the isostructural continuous film in the spectral region corresponding to the hole associated localized plasmon resonance. This is due to the increased electromagnetic field in the surrounding area of the resonant hole, and the subsequent additional contribution to the magnetic modulation of the continuous film. This novel concept that gives rise to enhanced magnetic field induced nonreciprocal effects can be of interest in the development of innovative platforms for sensing applications, optical isolators and modulators.

Mimicking electromagnetically induced transparency in the magneto-optical activity of magnetoplasmonic nanoresonators.

We show that the interaction between a plasmonic and a magnetoplasmonic metallic nanodisk leads to the appearance of magneto-optical activity in the purely plasmonic disk induced by the magnetoplasmonic one. Moreover, at specific wavelengths the interaction cancels the net electromagnetic field at the magnetoplasmonic component, strongly reducing the magneto-optical activity of the whole system. The MO activity has a characteristic Fano spectral shape, and the resulting MO inhibition constitutes the magneto-optical counterpart of the electromagnetic induced transparency.

Magnetic properties of encapsulated nanoparticles in nitrogen-doped multiwalled cabon nanotubes embedded in SiOx matrices.

We report the production, characterization, thermal transformations (400-1000 degrees C), and magnetic properties of nanoparticles encapsulated in nitrogen-doped multiwall carbon nanotubes (CNx-MWNT), which were embedded in silicon oxide (SiOx) matrices via sol-gel techniques. The vapor chemical deposition (CVD) method with ferrocene-benzelamine mixtures was used to synthesize Fe and Fe3C nanoparticles inside CNx-MWNTs. Composites consisting of CNx-MWNTs (filler) and SiOx (matrix) were fabricated and thermally treated to different temperatures and exposure times (t). All samples were characterized using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), thermogravimetic analysis (TGA), and magnetometry (vibrating sample). We found that upon thermal treatment, the ferromagnetic nanoparticles modify their morphology, composition and aspect ratio, thus resulting in drastic changes in the magnetic and structural properties. In particular, as produced encapsulated nanoparticles mainly consisting of Fe and Fe3C phases were thermally modified into magnetite (Fe3O4). We have also observed that the hysteresis loops are very sensitive to the thermal treatment of the sample. Thus we can control the magnetic properties of the samples using thermal treatments.