79 research outputs found
Ion distribution preferences in ternary crystals Zn xCd 1−x Te, Zn 1−x Hg xTe and Cd 1−x Hg xTe
No full textSimilar ternary semiconductors are sometimes associated with widely different structures characterized by different site occupation preferences. We have used far-infrared (FIR) spectra to determine the site occupation preference coefficients for three ternary semiconductor alloys: ZnCdTe, ZnHgTe and CdHgTe and, in the case of ZnHgTe, have validated it by X-ray absorption fine structure (EXAFS) analysis. While ZnCdTe spectra exhibit the canonical configuration with eight phonon lines free of vibrational defect lines and only a slight departure from a random ion distribution, CdHgTe spectra show the eight canonical phonon modes plus an additional vibrational defect line and constant preference coefficients. In contrast, two defect lines and only four modes characterize ZnHgTe spectra, as extreme preferences prevent the formation of two of the five expected tetrahedral configuration arrangements. Moreover, for this system, comparison with EXAFS data points out the vibrational nature of both the extra lines. The analysis clearly shows that assuming a Bernoulli distribution of the component configurations of semiconductors may lead to wrong assessments of the evolution of its properties with relative content.JRC.D.5 - Food Safety and Qualit
Manifestation of defects in phonon spectra of binary zinc-blende compounds
No full textIt is interesting to consider the problem of the presence of defects in the semiconductor binary compounds by observing their elemental tetrahedron distortions, caused by the creation of vacancies and interstitial atoms within the tetrahedra and so on. Our model thus considers the system A(Vz(x)Z(1-x)) and (A(1-y)Va(y))Z as composed of five defect tetrahedron configurations where A is a cation atom, Z an anion atom, V-alpha-cation vacancy, V-z-anion vacancy. In this communication we present far IR (FIR) spectra obtained at the DAFNE facility of Laboratori Nazionali di Frascati (INFN) using its synchrotron radiation. Two samples of CdTe are considered: sample-1 was grown by the PVT technique and sample-2 using the same technique but on the basis of, polycrystalline CdTe previously purified from oxygen in hydrogen atmosphere
First interpretation of phonon spectra of quaternary solid solutions using fine structure far-IR reflectivity by synchrotron radiation
No full textIn this work, we present and discuss far-infrared (FIR) reflectivity spectra obtained using infrared synchrotron radiation in different ZnxCdyHg1-x-yTe (ZMCT) quaternary alloys. Reffectivity spectra were measured at the DAFNE-light facility of the INFN-LNF with samples placed under vacuum inside a BRUKER Equinox 55 interferometer. Samples were cooled in a helium cryostat in a temperature range from about 20 K to 300 K. The obtained spectra were standard Kramers-Kronig transformed to obtain the imaginary part of the dielectric functions, then unfolded into a set of Lorentzian oscillators. The fitting procedure yields a total of 21 lines in the ZnxCdyHg1-x-yTe reflection spectra of these quaternary alloys. Sixteen lines have been correlated to ternary spectral contributions of the different components: CdHgTe, ZnHgTe and CdZnTe (with a precision of +/- 1.5cm(-1)). In the wave number range between 108 cm(-1) and 190 cm(-1) the oscillator frequencies have been attributed to the spectral lines of these quaternary alloys. (c) 2006 Elsevier B.V. All rights reserved
Neutron activation analysis of Antarctic coastal marine sediments. Report GE/R/SP/07/94, (1994), 5 p. European Commission, Joint Res. Centre, IRMM, Geel (Belgium).
No full textOccupation preference values in doped CmIm' multinaries from EXAFS and FTIR correlative analysis
No full textWe discuss which x-ray absorption fine structure (EXAFS) data of binary doped CmIm' compound structures can be unfolded to determine elemental bond distances and the deviations from random configurations due to site preference occupations (SOPs). SOP-deviation estimations can be further confirmed by independent Fourier transform infrared (FTIR) data analysis. The limits and restrictions of our model are presented and discussed.The authors would like to thank A. Balerna for constructive comments. The work was partially supported by the European Community Research Infrastructure Integrating Activity “Study of Strongly Interacting Matter–Hadron Physics” (cf. contract number RII-CT-2004-506078) of the Sixth Framework Programme (FP6)
Occupation preference values in doped CmIm' multinaries from EXAFS and FTIR correlative analysis
No full textWe discuss which x-ray absorption fine structure (EXAFS) data of binary doped CmIm' compound structures can be unfolded to determine elemental bond distances and the deviations from random configurations due to site preference occupations (SOPs). SOP-deviation estimations can be further confirmed by independent Fourier transform infrared (FTIR) data analysis. The limits and restrictions of our model are presented and discussed.The authors would like to thank A. Balerna for constructive comments. The work was partially supported by the European Community Research Infrastructure Integrating Activity “Study of Strongly Interacting Matter–Hadron Physics” (cf. contract number RII-CT-2004-506078) of the Sixth Framework Programme (FP6)
Occupation preference values in doped CmIm' multinaries from EXAFS and FTIR correlative analysis
No full textWe discuss which x-ray absorption fine structure (EXAFS) data of binary doped CmIm' compound structures can be unfolded to determine elemental bond distances and the deviations from random configurations due to site preference occupations (SOPs). SOP-deviation estimations can be further confirmed by independent Fourier transform infrared (FTIR) data analysis. The limits and restrictions of our model are presented and discussed.The authors would like to thank A. Balerna for constructive comments. The work was partially supported by the European Community Research Infrastructure Integrating Activity “Study of Strongly Interacting Matter–Hadron Physics” (cf. contract number RII-CT-2004-506078) of the Sixth Framework Programme (FP6)
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