Scielo RSS <![CDATA[Superficies y vacío]]> vol. 27 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Growth of polyhedral stacked micro columns and micro particles of zinc by thermal evaporation and condensation technique</b>]]> Metallic zinc nano structures have been grown by the thermal evaporation and condensation technique using a mixture of zinc and manganese oxide powders and nitrogen as carrier gas. 650 °C and 1 atm were used as processing temperature and pressure, respectively. It was found that the shape of zinc structures is dependent on the source materials. When a mixture of Zn/MnO2 powders is used as raw material micro-particles with oblate spherical shape and micro-columns are obtained. On the other hand, when only zinc powder is used as source material, spherical stones without facets are deposited. It is assumed that evaporation from the source is inhibited when a mixture of Zn and MnO2 is used. Therefore, supersaturation downstream from the source changes and as a consequence the morphology of the structures is modified. Synthesized material is make-up of zinc atoms and no other impurities or catalytic particles were detected according to elemental analysis. Vapor-solid is though as mechanism for growing those zinc structures. <![CDATA[<b>Quantification of phase content in TiO<sub>2</sub> thin films by Raman spectroscopy</b>]]> Recently, it has been reported that TiO2 with mixture of phases (anatase/rutile) exhibit higher photocatalytic activity than TiO2 with pure anatase phase. Therefore, the production and correct quantification of the ratio of phases becomes an important task. In this work, anatase TiO2 thin films were obtained by the DC reactive magnetron sputtering technique. TiO2 with mixture of phases (anatase/rutile) were prepared by thermal annealing of the as-deposited thin films. The value of the anatase/rutile ratio in the titanium dioxide thin films was estimated using Raman spectroscopy. Additionally, it is reported the dependence of the bandgap of the TiO2 thin films as a function of the anatase/rutile ratio. The band gap of the TiO2 thin films was determined from diffuse reflectance measurements. <![CDATA[<b>Síntesis de puntos cuánticos de CdTe mediante la técnica de ablación láser de sólidos en líquidos</b>]]> En este trabajo se presentan resultados sobre la caracterización de puntos cuánticos (PCs) en un medio líquido (acetona) obtenidos por ablación láser a partir de un blanco de Teluro de Cadmio (CdTe). La ablación de CdTe se llevó a cabo mediante un láser de Nd-YAG con pulsos láser de 30 picosegundos. Con el propósito de variar la concentración en la solución de PCs, se realizaron experimentos a diferentes tiempos de irradiación. Las soluciones coloidales de CdTe fueron caracterizadas por espectroscopia UV-Vis y de fotoluminiscencia. El tamaño y forma de los puntos cuánticos generados se determinaron por microscopía electrónica de transmisión (TEM, HRTEM), de donde se confirmó la obtención de nanoestructuras con geometría esférica con una distribución de tamaños entre 4 y 200 nm, centrado en 6 nm. El espectro de fotoluminiscencia de los puntos cuánticos en solución mostró una banda de emisión centrada en 488 nm cuando se excita con luz ultravioleta de 369 nm.<hr/>In this paper we report results of the characterization of quantum dots (QDs) in acetone solution obtained by laser ablation of a cadmium telluride (CdTe) target. The laser ablation of CdTe was carried out by using pulses of 30 ps from a Nd: YAG laser. With the aim of varying the concentration of QDs in the solution, samples at different irradiation times were obtained. CdTe-colloidal solutions were characterized by UV-Vis and photoluminiscence spectroscopy. The size and shape of the quantum dots were obtained by transmission electron microscopy (TEM, HRTEM), showing spherical geometry nanostructures with a size distribution within a range of 4-200 nm, (average diameter of 6 nm. The photoluminescence spectra of CdTe quantum dots solutions show a broad band emission centered at 488 nm when the samples are excited 369 nm. <![CDATA[<b>Colloidal gold nanofilms fabricated via self-assembled monolayer and Langmuir-Blodgett methods</b>]]> Colloidal gold nanoparticles have been used as biomaterials since the 1970's. The main goal of developing biological sensors is to identify a number of human diseases and infections with high specificity and sensibility. Two of the most used methods to fabricate biofilms are the Langmuir-Blodgett and the Self-Assembled Monolayer techniques, which are used to obtain homogenous organic and inorganic monolayer films and thin films of organic compounds, respectively. We describe the fabrication of ring-structure colloidal gold nanofilms using both methods. Nanofilms were further characterized by X-Ray Diffraction, Fourier Transformed Infrared Spectroscopy, Ultraviolet-Visible Spectroscopy, and Atomic Force Microscopy. <![CDATA[<b>Polycristalline growth of zinc blende gallium arsenide layers by R.F. magnetron sputtering</b>]]> Zinc-blende GaAs layers were prepared on (100) Si and glass substrates by r.f. magnetron sputtering. The morphology of GaAs layers is analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (FE-SEM), to determine the sample topography and growth type. The compositional analysis was performed by means of energy dispersive X-ray spectroscopy (EDS), in order to obtain information of the atomic percentages of the elements and their spatial distribution in the samples. The optical properties of the layers are discussed from the results of UV-Vis absorption, and Photoacoustic spectroscopy (PAS). Finally, the Raman shift of the GaAs phonon modes are studied as function of the penetration depth of laser wavelength used to excite the sample on Raman microscopy.