Quantification of phase content in TiO2 thin films by Raman spectroscopy

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

Electron evaporation of carbon using a high density plasma

High-density plasmas are often used either in the preparation of thin films or for the modification of surfaces; nitriding. However, except for collision-driven chemical reactions the electrons present are not used, although electron bombardment heating of the work piece nearly always occurs. Principally it is the ions and neutrals that are utilised for materials processing. By suitable biasing of a conducting source material the electrons can be extracted from a highdensity low-pressure plasma to such an extent that evaporation of this source material can be achieved. Due to the presence of the plasma and the flux of electrons a large proportion of the evaporant is expected to be ionised. We have used this novel arrangement to prepare thin films of carbon using a resonant high-density argon plasma and a water cooled rod of high purity graphite. Multiple substrates were used both outside of, and immersed in, the plasma. We report the characteristics of the plasma (electron temperature and density, the ion energy and flux, and optical emission spectra), the deposition process (the evaporation rate and ion/neutral ratio), and the film properties (IR and UV/Vis absorption spectra, Raman spectra, elemental analysis, hardness and refractive index

Insecticide activity of bifenthrin nanoparticles synthesized by laser ablation of solids in liquids

ARTICULO DE INVESTIGACIONARTICULO DE INVESTIGACIO

Caracterización de bicapas TiO2/SnO2 depositadas por ablación láser para fotocatálisis

Se depositaron películas delgadas de oxido de estaño y oxido de titanio sobre sustratos de vidrio usando la técnica de ablación láser. Los depósitos obtenidos fueron amorfos y con el propósito de obtener las fases cristalinas se sometieron a tratamientos térmicos. La caracterización de las películas depositadas incluyó composición (EDS y EFA), micro-estructura (espectroscopia Raman y XRD), morfología superficial (SEM), propiedades ópticas (UV-Vis) y resistividad. Los resultados de la caracterización estructural muestran que en el caso del oxido de estaño se obtiene la fase casiterita, mientras que en el caso del oxido de titanio se obtuvo la fase anatasa. En ambos casos los resultados de composición muestran que se obtienen los óxidos estequiométricos, siendo uniformes en profundidad. Las capas de oxido de estaño muestran resistividades del orden de 4.2 x10-2 ohm-cm, y las bicapas una transparencia óptica del 65 % en el intervalo de 400 a 700 nm. Las bicapas obtenidas tienen propiedades que las hacen potencialmente útiles en fotocatálisis