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- Author or Editor: H. Rausch x
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Abstract
Investigations of insulating silicon dioxide films formed on silicon epitaxial layers are reported. Activation analysis and surface autoradiography were used to determine the concentration distribution and precipitation of contaminants in the internal part of the films and on the surfaces. The aim of this work was to study the origin of the contaminants by sampling each technological product following thermal oxidation, doped oxide deposition, heating and metallizing. Under the given conditions the following detection limits of impurities could be obtained in silicon dioxide films: Na=80 ppb, Sb=100 ppb, Cu=20 ppb and Au=5 ppb.
Abstract
Activation analysis and autoradiography were used to investigate the concentration distribution of contaminants in poly-Si−Si3N4−SiO2−Si substrate multilayer structures (SNOS) on sampling each technological product. Samples were irradiated for 36 hrs at a thermal neutron flux of 4·1013n·cm−2·sec−1. The thin films of the analysed sample were removed stepwise by selective chemical etching using appropriate masking techniques. Simultaneously autoradiographs were made of the surface of parallel samples activated under the same conditions. The concentration of the technological contaminants (e.g. Na, Cu, Au) increases in the junction interface of the layers as unambiguously shown by the results obtained.
Abstract
The use of nuclear recoil for producing radioactive endohedral and cage-labeled fullerenes is presented, with special emphasis on the energy of chemical effects after nuclear particle capture. The different possibilities using (n,
), (n,
), (p,n), (g,n) and (,n) and (,n) nuclear reactions are treated in detail.
Abstract
Investigations have been made concerning the determination of special contaminants (e.g. oxygen, boron) in the surface layers or epitaxially grown layers of semi-conductor crystals. These contaminants are insensitive to the conventional (n, γ) analysis and for their activation charged particles (e.g. t, α) from nuclear reactions induced by the capture of reactor neutrons are used. The specific particle yield from such reactions, e.g.6Li(n,t)α, was studied. The optimum conditions for the producing of activating layers (containing Li) and their optimum contact with the sample under investigation are discussed. Considering the so-called activation depth, a method was developed for the appropriate removal of the activated layer and the elements to be determined are subsequently separated from the semiconductor matrix by a fast chemical procedure. The combined activation cross sections measured on standard samples are given for different compositions and species of activating layers.
Résumé
On rapporte les recherches faites sur les couches épitaxiques déposées sur des substrats dopés en arsenic, antimoine et phosphore. On étudie les couches critiques par analyse par activation et autoradiographie. On détermine les répartitions des concentrations des éléments dopants et des traces d'impuretés les plus fréquentes, telles que l'or, le cuivre et le sodium, dans la couche superficielle et dans l'interface film-substrat des couches homoépitaxiques de silicium. Dans les conditions expérimentales données, on trouve que la concentration contaminante minimum décelable est d'environ 1013 atomes/cm3.
Abstract
Various methods (e.g. spreading resistance and C-V measurements, neutron activation analysis, SIMS) have been used to determine concentration distributions of antimony dopant and charge carriers in single and double epitaxial silicon layers. Comparing the results obtained by the methods, an increased dopant diffusion process could be observed in the epitaxial layer during neutron irradiation of the sample, which arose as a systematic error in the NAA method. The origin of the deviations is discussed.
Abstract
The chemical composition of brown coal fuels and several sedimental type atmospheric particulate pollutants of industrial origin (e.g. fly-ash, bottom-ash, dust particulates from foundry-halls and casting-halls) was studied in relation to their toxic and their natural radioactive contents. In addition, some agricultural crops (e.g. soya bean, sunflower, rape, barley and luceme) sampled, in the near vicinity within a radius of about 10 km of the industrial centre were also analysed for significant distributions of any toxic components. Because of the high uranium and thorium concentrations in Hungarian coal fuels and, consequently, in various fly-ash particulate pollutants, the natural gamma activities of the samples were also measured and the relevant equilibriu states of the232Th and238U natural decay series were studied.
Abstract
In an interlaboratory comparison four samples of monocrystalline silicon were analyzed sequentially by INAA in four laboratories. The results obtained demonstrate the possiblity of repeated use of silicion samples for interlaboratory comparisons. *** DIRECT SUPPORT *** A0653052 00003
Abstract
By using instrumental neutron activation analysis (INAA) it has been shown that some pristine carbon SWNT's and MWNT's of different makes, contain a multitude of trace element impurities at various concentration levels including also amounts which can be considered as nanoelectronically dopant quantities. The same holds for the above mentioned carbon nanotubes also after their inadequately so-called purification.
