Transparent conducting thin films by the co-sputtering of ZnO-ITO targets

Transparent and conductive Zn-In-Sn-O (ZITO) amorphous thin films have been deposited at room temperature by the rf magnetron co-sputtering of ITO and ZnO targets. Co-sputtering gives the possibility to deposit multicomponent oxide thin films with different compositions by varying the power to one of the targets. In order to make ZITO films with different Zn content, a constant rf power of 50 W was used for the ITO target, where as the rf power to ZnO target was varied from 25 W to 150 W. The as deposited films showed an increase in Zn content ratio from 17 to 67 % as the power to ZnO target was increased from 25 to 150 W. The structural, electrical and optical properties of the as deposited films are reported. The films showed an average transmittance over 80% in the visible wavelength range. The electrical resistivity and optical band gap of the ZITO films were found to depend on the Zn content in the film. The ZITO films deposited at room temperature with lower Zn content ratios showed better optical transmission and electrical properties compared to ITO film.

Competing tunneling and capacitive paths in Co-ZrO2 granular thin films

The ac electrical response is studied in thin films composed of well-defined nanometric Co particles embedded in an insulating ZrO2 matrix which tends to coat them, preventing the formation of aggregates. In the dielectric regime, ac transport originates from the competition between interparticle capacitive Cp and tunneling Rt channels, the latter being thermally assisted. This competition yields an absorption phenomenon at a characteristic frequency 1/(RtCp), which is observed in the range 1010 000 Hz. In this way, the effective ac properties mimic the universal response of disordered dielectric materials. Temperature and frequency determine the complexity and nature of the ac electrical paths, which have been successfully modeled by an Rt-Cp network.

Synthesis, structural order and magnetic behavior of self-assembled epsilon-Co nanocrystal arrays

The synthesis of magnetic nanoparticles with monodispere size distributions, their self assembly into ordered arrays and their magnetic behavior as a function of structural order (ferrofluids and 2D assemblies) are presented. Magnetic colloids of monodispersed, passivated, cobalt nanocrystals were produced by the rapid pyrolysis of cobalt carbonyl in solution. The size, size distribution (std. dev.< 5%) and the shape of the nanocrystals were controlled by varying the surfactant, its concentration, the reaction rate and the reaction temperature. The Co particles are defect-free single crystals with a complex cubic structure related to the beta phase of manganese (epsilon-Co). In the 2D assembly, a collective behavior was observed in the low-field susceptibility measurements where the magnetization of the zero field cooled process increases steadily and the magnetization of the field cooling process is independent the temperature. This was different from the observed behavior in a sample comprised of disordered interacting particles. A strong paramagnetic contribution appears at very low temperatures where the magnetization increases drastically after field cooling the sample. This has been attributed to the Co surfactant-particle interface since no magnetic atomic impurities are present in these samples.

Competing tunneling and capacitive paths in Co-ZrO2 granular thin films

The ac electrical response is studied in thin films composed of well-defined nanometric Co particles embedded in an insulating ZrO2 matrix which tends to coat them, preventing the formation of aggregates. In the dielectric regime, ac transport originates from the competition between interparticle capacitive Cp and tunneling Rt channels, the latter being thermally assisted. This competition yields an absorption phenomenon at a characteristic frequency 1/(RtCp), which is observed in the range 1010 000 Hz. In this way, the effective ac properties mimic the universal response of disordered dielectric materials. Temperature and frequency determine the complexity and nature of the ac electrical paths, which have been successfully modeled by an Rt-Cp network.

Ab initio study of MF2 (M=Mn, Fe, Co, Ni) rutile-type compounds using the periodic unrestricted Hartree-Fock approach

The ab initio periodic unrestricted Hartree-Fock method has been applied in the investigation of the ground-state structural, electronic, and magnetic properties of the rutile-type compounds MF2 (M=Mn, Fe, Co, and Ni). All electron Gaussian basis sets have been used. The systems turn out to be large band-gap antiferromagnetic insulators; the optimized geometrical parameters are in good agreement with experiment. The calculated most stable electronic state shows an antiferromagnetic order in agreement with that resulting from neutron scattering experiments. The magnetic coupling constants between nearest-neighbor magnetic ions along the [001], [111], and [100] (or [010]) directions have been calculated using several supercells. The resulting ab initio magnetic coupling constants are reasonably satisfactory when compared with available experimental data. The importance of the Jahn-Teller effect in FeF2 and CoF2 is also discussed.

Sociedad del riesgo, producción y sostenibilidad

El concepto sociedad del riesgo se basa en la constatación de que, en las sociedades actuales, la producción social de riqueza va acompañada por una creciente producción social del riesgo. La progresión y el aumento de estos riesgos está teniendo consecuencias políticas y económicas claras. Un primer efecto directo consistiría en la implementación de políticas gubernamentales orientadas al control y a la reducción de los mismos, como consecuencia directa de la mayor visibilidad que, para la opinión pública, tienen los problemas ambientales. De la misma manera que, desde una perspectiva económica, podemos establecer un claro paralelismo entre la teoría de la modernización ecológica y las nuevas estrategias ecoproductivas. Este artículo pretende dar una visión general de todo este proceso partiendo del concepto sociedad del riesgo para, con posterioridad, establecer paralelismos con las nuevas estrategias ecoproductivas, con el proceso de modernización ecológico y con una última reflexión: ¿caminamos hacia un nuevo modelo productivo?.

Producción y comercio de cereal en el NE de la Península Ibérica entre los siglos VI-II a.c.

Análisis de la problemática de la producción de excedentes cerealísticos en el ámbito de la Cultura Ibérica del NE. peninsular, así como de su posterior comercialización, a través de Emporion y Massalia, hacia los mercados del Mediterráneo central y el Atica. El estudio se basa en la comparación de la información proporcionada por las fuentes clásicas, con la obtenida mediante modelos teóricos de productividad.

Producción cerámica en Catalunya en la Edad del Bronce: el ejemplo de la cueva de Les Pixarelles

La cerámica aparecida en la cueva de Les Pixarelles proporciona un conjunto ideal para estudiar la evolución de las producciones cerámicas desde la fase final del Neolítico hasta el Bronce final en Catalunya. El estudio diacrónico de las cerámicas se ha basado en la combinación del estudio tipológico y estilístico y en un estudio petrográfico que ha permitido caracterizar diversas fábricas. Las diferencias observadas responden a la utilización de diversas materias primas y a la utilización de diferentes técnicas de preparación de pasta que revelan una interesante complejidad para la producción cerámica de la zona.