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- Shiryaev, A.A., et al.
(author)
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Isotopic heterogeneity in synthetic and natural silicon carbide
- 2008
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In: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 69:10, s. 2492-2498
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Journal article (peer-reviewed)abstract
- The distribution of both carbon and silicon isotopes in synthetic sublimation growth SiC wafers and in natural SiC grains was studied using secondary ion mass-spectrometry (SIMS). Significant variations in both isotopic ratios were observed which were broadly correlated with the crystalline perfection as documented by Raman microspectroscopy. Domains consisting of 15R (or with its admixture) are, on average, enriched in 12C isotope relative to 6H domains, and they also show larger scatter in their observed silicon isotope ratios. We ascribe such heterogeneity to fluctuations of Si/C ratio in the growth medium and it is possible to model the spatial extent of such fluctuations. For the natural SiC grains the isotopic data suggest that they grew under relatively stable conditions, although some of them show significant isotopic zoning.
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- Vilensky, A.I., et al.
(author)
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THERMAL REGRESSION OF LATENT TRACKS IN THE POLYMER IRRADIATED BY HIGH ENERGY HEAVY IONS
- 2004
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In: Nuclear Instruments and Methods in Physics Research B. ; 218, s. 294-299
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Journal article (peer-reviewed)abstract
- Influence of heat treatment (85-180 oC) on latent tracks (LTs) in poly(ethylene terephthalate) (PET) films irradiated by Xe ions with energy of 1 MeV/nucleon was studied. Kinetics of the alkaline etching (layer-by-layer technique) was investigated. Thermal annealing rises the time of through-pore formation. The etching of through pores, investigated by Hagen-Poiseuille and atomic force microscopy (AFM) methods, was found to be non-linear: steps were discovered at the etching diagram. They were associated with earlier detected zones of high chemical stability around the track (with the diameters of approximately 10 and 20 nm). Using AFM method an appearance of surface craters after the irradiation was found. After the annealing the shape of these defects changed to the hillock form. From analysis of the Raman and electron paramagnetic resonance (EPR) spectra it is supposed that polymer structure in LT area was changed towards carbonaceous phase with graphite-like inclusions, which is evolving under the annealing and effecting the sequential etching process.
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