Abstract.  Total ionization cross sections of neutral phosphorus, arsenic, antimony, and bismuth atoms by electron impact are reported and compared to the only available experimental results by Freund et al. [Phys. Rev. A 41, 3575 (1990)]. These calculations take into account the possibilities that some target atoms used in the experiments were in metastable states close to the ground state, the excitation-autoionization of nsnp4 excited states may be substantial, and the ions produced in experiments may be in excited, low-lying metastable states. The cross sections for direct ionization calculations are based on the BEB model by Kim and Rudd [Phys. Rev. A 50, 3954 (1994)]. Plane-wave Born cross sections scaled by the method developed by Kim [Phys. Rev. A 64, 3954 032713 (2001)] are used to determine the contributions from excitation-autoionization. The combination of the BEB model and the scaled Born cross sections is in agreement with the experimental data by Freund et al. These theoretical data are useful to experimentalists and can be used to complete data tables needed for plasma or astrophysical studies.

Abstract.  Total ionization cross sections of neutral phosphorus, arsenic, antimony, and bismuth atoms by electron impact are reported and compared to the only available experimental results by Freund et al. [Phys. Rev. A 41, 3575 (1990)]. These calculations take into account the possibilities that some target atoms used in the experiments were in metastable states close to the ground state, the excitation-autoionization of nsnp4 excited states may be substantial, and the ions produced in experiments may be in excited, low-lying metastable states. The cross sections for direct ionization calculations are based on the BEB model by Kim and Rudd [Phys. Rev. A 50, 3954 (1994)]. Plane-wave Born cross sections scaled by the method developed by Kim [Phys. Rev. A 64, 3954 032713 (2001)] are used to determine the contributions from excitation-autoionization. The combination of the BEB model and the scaled Born cross sections is in agreement with the experimental data by Freund et al. These theoretical data are useful to experimentalists and can be used to complete data tables needed for plasma or astrophysical studies.

Portugal has been providing dinosaur remains since, at least, 1863. The 18th century tiles depicting the legend of Our Lady in Cabo Espichel are probably the oldest known dinosaur track illustration. To our knowledge, the first remains found in Portugal were theropod teeth collected near Porto das Barcas (Late Jurassic of Lourinhã) in June 20th, 1863 by the geologist Carlos Ribeiro (1813-1882). The first dinosaur paper was written by Henri Sauvage (1842-1917) published in 1896. All remains collected since 19th century were gathered in a work signed by Albert de Lapparent (1905-1975) and Georges Zbyszewski (1909-1999 ) titled Les Dinosauriens du Portugal (1957) that was a significant milestone in the Portuguese dinosaur paleontology and gives the state-of-the-art by the time. Several dinosaurs are named, described, depicted and mapped in that monograph. The first track record is given by Jacinto Pedro Gomes (1844-1916) in 1916. Concerning the non-scientific literature referring to dinosaurs, in 1884 the newspaper Occidente reports the Bernissart findings in Belgium. In the 1959 occurs the first visit to Portugal of Walter Kühne (1911-1991) from the Free University of Berlin. Further visits and work granted the access to the Guimarota Mine and other Late Jurassic deposits in the 1960’s, 70’s and 80’s with a high number of publications. In the 1980’s and early 1990’s starts a progressive era for dinosaur paleontology in Portugal with the works of Peter Galton, Miguel Telles Antunes, the Natural History Museum, the Museum of Lourinhã and the New University of Lisbon, Oliver Rauhut, and others.

n/a

n/a

n/a

In this work, it is demonstrated the application of a high k dielectric, as hafnium oxide (HfO2), in poly-Si thin film transistors (TFTs) obtained by metal induced lateral crystallization (MILC). The dielectric layer was deposited at room temperature by sputtering, using argon and oxygen as process gases. As produced TFTs exhibit field effect mobility around 45 cm2 V-1 s-1and Ion/Ioff ratio of about 2 × 105. After annealing in a forming gas atmosphere for about 1 h at 200 °C, the threshold voltage and the sub-threshold slope are reduced, respectively from 4.8 to 2 V and from 1.6 to 1.4 V/dec. Nevertheless, by doing so, we notice a reduction on the field effect mobility of about 45% and a decrease of about 2.5 times on the Ion/Ioff ratio. Longer annealing time will not improve the TFT's performance. © 2008 Elsevier B.V. All rights reserved.

n/a

n/a

n/a

n/a

n/a

n/a

In this work, the mechanical characterization of ceramic products processed from red clay with different amounts of added coal fly ash was investigated. Coal fly ash produced by power plants is a waste material that constitutes an alternative source of minerals for the production of traditional building ceramics, as it is a complex mixture of several oxides such as SiO2, Al2O3, CaO, Fe2O3, Na2O, TiO2, which are usually present in the composition of such ceramics. A powder technology and firing route was followed for the processing of the clay and coal fly ash based ceramics. Different proportions of waste (10, 25 and 50%, by weight) were added to red clay, and then the mixed powders were pressed to form compacts that were fired at a selected temperature in the range 850-1,150°C. The effects of waste content and of heating conditions on the microstructure and mechanical characteristics of the obtained materials were investigated. The density, porosity, water absorption, flexural strength, hardness and fracture toughness of the produced materials were evaluated. A comparison was made between the properties of the produced ceramics with those of traditional ceramic materials used in construction, e.g. floor or wall tiles, and it was observed that the clay based products with coal fly ash additions may be used in similar applications. © 2007 Springer Science+Business Media B.V.

n/a

In this paper a new approach is presented for the simulation of spectroscopic ellipsometry (SE) data to estimate the level of nickel (Ni) contamination in silicon crystallized by metal induced crystallization (MIC). The method employs the addition of Ni as reference for a Bruggemann effective medium approximation (BEMA) to simulate the optical response of the crystallized silicon. This new approach is sensitive to changes in the initial average metal thickness used on the crystallization process to thickness values as low as 0.05 nm. This corresponds to a volume fraction of 0.24%, confirmed by Rutherford backscattering spectrometry (RBS) where it was observed that the Ni volume fraction detected by SE varies linearly with the metal amount inside the crystallized films determined by RBS. © 2008.

n/a

The paper presents the properties of zinc oxide thin films deposited on glass substrate via dip-coating technique. Zinc acetate dehydrate, ethanol and monoethanol amine were used as starting materials and N2 gas was used as thermal annealing atmosphere for film crystallization. The effect of withdrawal speed on the crystalline structure, morphology, zinc and nitrogen chemical states, optical, electrical and gas-sensing properties of the thin films has been investigated using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, optical transmittance and photoreduction-ozone reoxidation data. © 2007 Elsevier B.V. All rights reserved.

n/a

n/a

n/a

n/a

n/a

n/a

n/a