O3-Annealing Effect on the Etching Resilience of a TiO2/Al2O3 filter Prepared by Atomic Layer Deposition.

This research investigates the improvements of ozone (O3) annealing on the optical and etching characteristics of TiO2/Al2O3 multilayer band-pass filters designed for potential optoelectronic applications. The band-pass filters were fabricated using atomic layer deposition (ALD), and their performance was systematically analyzed after the addition of O3 annealing at moderate temperatures (up to 300 °C). Results reveal that O3 annealing improves the optical transmittance of the multilayers by approximately 40% without significant spectral changes (∼6 nm). The observed enhancement in the transmittance is attributed to the improved stoichiometry of TiO2. By filling in the oxygen vacancies created during the fabrication process, it reduces its extinction coefficient. Furthermore, the O3 annealing enhances the stability of TiO2 against wet etching, improving the uniformity of etched surfaces. Etching on the ozone-annealed multilayer was up to 8 times more homogeneous, as observed in the roughness. The relatively short duration of the O3 annealing process, approximately 1.6 h, makes it a cost-effective alternative compared to using ozone in the ALD process, which can last several hours for thick optical coatings.

Spectroscopic Ellipsometry Study on Tuning the Electrical and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition.

This work reports the ellipsometry analysis of atomic layer deposition (ALD) films of ZnO doped with Zr to determine parameters like free carrier concentration and mobility. Thin films of zinc oxide (ZnO) and Zr-doped ZnO of thickness ∼100 nm were prepared by atomic layer deposition on sapphire, SiO2/Si(100), and Si(100) substrates. Variable-angle spectroscopic ellipsometry was used to study their optical properties in the 0.5-3.5 eV spectral range. The optical constants were accurately obtained using a model that combines Drude and Tauc-Lorentz oscillators with Bruggeman effective medium approximations, allowing the inclusion of a roughness layer in the optical model. The effect of Zr doping (ca. 1.9-4.4 atom %) was then investigated in both as-prepared samples and samples annealed in the temperature range of 100-300 °C. All of the films exhibited good optical transparency (ca. 70-90% in the visible region). For doping levels below 2.7 atom %, the real part of the dielectric permittivity reveals a semiconductor-to-metal transition in the near-infrared (NIR) region, as the permittivity goes from positive to negative. Besides, the plasma energy increases with increasing Zr concentration, and both resistivity and carrier concentration exhibit slightly parabolic behaviors, with a minimum of ∼1.5 × 10-3 Ω cm and a maximum of 2.4 × 1020 cm-3, respectively, at the same critical Zr concentration (2.7 atom %). In contrast, the carrier mobility decreases rapidly from 76.0 to 19.2 cm2/(V s) with increasing Zr content, while conductivities and carrier mobilities worsen when the annealing temperature increases, probably due to the segregation of ZnO crystals. Finally, the optical band gap is very stable, revealing its interesting independence of substrate composition and annealing temperature, as it collapses to a single master curve when band gap energy is plotted versus free carrier concentration, following the Burstein-Moss effect. Overall, the Zr-doped ZnO films studied here would be a highly desirable system for developing thermally stable transparent conductive oxides (TCOs).

Cobertura de vacunación contra sarampión en menores de 5 años, comuna Provenza, Bucaramanga, marzo de 2003 / Measles vaccine coverage in children less than 5 years of age in the Provenza district, Bucaramanga, march, 2003

Introducción: El sarampión es una enfermedad viral aguda muy contagiosa que causa epidemias graves sobre todo en niños. En el año 2002 se presentó una epidemia que afectó a Venezuela y Colombia causando gran morbimortalidad. Las medidas tomadas fueron: vacunar todo niño entre 6 meses y 5 años de edad, alcanzar coberturas de vacunación mayores del 95 por ciento y evaluar dichas coberturas. Objetivo: Determinar coberturas de vacunación contra sarampión en una comuna de Bucaramanga. Métodos: Estudio de corte transversal. De cada barrio se seleccionaron aleatoriamente cuatro manzanas Se aplicó una encuesta casa a casa hasta completar 50 viviendas con al menos un menor de cinco años. Se averiguó estado de vacunación y se contrastó con carné. Resultados: Se encuestaron 1768 viviendas; en 400 se encontraron 488 menores de 5 años, 433 entre 6 y 60 meses. 412 (95.2 por ciento) manifestaban estar vacunados y 279 (64.4 por ciento) mostraron carné de vacunación. Las razones para no vacunación fueron: descuido, distancia, ausencia de la mamá. Las razones de no mostrar carné fueron: estaba en el colegio o el cuidador no lo encontró. Conclusión: La cobertura de vacunación en la comuna de Provenza está por encima del 64 por ciento con carné y del 95.2 por ciento por autoinforme