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Analysis of Atmospheric Aerosols Using the Lisbon Nuclear Microprobe

100%

Rita E., Alves L., Reis M., Rodrigues F., Fialho P., Soares J.

Acta Physica Polonica A

2001

vol. 100

issue 5

781-788

The nuclear microprobe installed at Instituto Tecnológico e Nuclear, in Lisbon, was used in the analysis of aerosols collected at the Azores islands. Samples from two different aerosol groups were analysed. One referred to aerosols that were carried from North America and the other one contained aerosols that were carried from the Sahara desert and crossed over Europe. Coarse and fine fractions were analysed for each aerosol group and two-dimensional elemental maps were constructed, which allowed the identification of several individual particles. For particles of interest, elemental spatial correlations and dimensions were determined and point analysis was also carried out (depth information was achieved by fitting Rutherford backscattering spectra). Some of these particles are quite interesting. For instance, in the fine fraction of the aerosols that were carried from North America, particles were found with Cu and Cl in the atomic proportion 1:2 and with dimensions 15×15×15μm^3, and in the corresponding coarse fraction a particle with K and S was identified, with dimensions 28×35×30μm^3. Some differences were found between the aerosols groups. One example of these are Ti particles (fine fraction) and Rb (coarse fraction) that were identified in one group (Sahara desert and Europe), but not in the other

Combined Analyses of Ion Beam Synthesized Layers in Porous Silicon

84%

Ramos A., Pászti F., Horváth Z., Vázsonyi É., Conde O., da Silva M., da Silva M., Soares J.

Acta Physica Polonica A

2001

vol. 100

issue 5

773-780

High dose ion implantation was used to form polycrystalline silicide films on porous silicon with different native concentrations of light impurities (C and O). Porous silicon layers severalμm thick were implanted with 170 keV Cr^+ ions to fluences of 3×10^{17} ions/cm^2 both at room temperature and 450^ºC. Similar samples were implanted with 100 keV Co^+ ions to fluences of 2×10^{17} ions/cm^2 at room temperature, 350ºC, and 450ºC. The formed silicide compounds were studied by Rutherford backscattering spectrometry, elastic recoil detection, glancing incidence X-ray diffraction, and four point-probe sheet resistance measurements. Selected Co implanted samples were analysed by cross-section transmission electron microscopy. Results show that the light impurities were partially expelled from the forming silicide layer. Combining cross-section transmission electron microscopy with ion beam methods it was possible to show that, in the implanted region, the porous structure collapses and densifies during implantation, but the underlying porous silicon remains intact. The layer structure, as well as the quality and type of the formed silicide, were found to depend on the original impurity level, implantation temperature, and annealing.

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2 Acta Physica Polonica A

2 2001

2 Soares J.

1 Alves L.

1 Conde O.

1 Fialho P.

1 Horváth Z.

1 Pászti F.

1 Ramos A.

1 Reis M.

1 Rita E.

1 Rodrigues F.

1 Vázsonyi É.

1 da Silva M.

Search results

Analysis of Atmospheric Aerosols Using the Lisbon Nuclear Microprobe

Combined Analyses of Ion Beam Synthesized Layers in Porous Silicon