The local crystalline structure of ZnCdTe alloys obtained by Far Infrared Synchrotron Radiation measurements

Jacek Polit 1A Kisiel 3B V. Robouch 5Eugen M. Sheregii 1J Cebulski 1Andrzej Mycielski 2E Burattini 5M Cestelli Guidi 4M Piccinini 5A Nucara 4Augusto Marcelli 5

1. University of Rzeszow, Institute of Physics, Rejtana 16, Rzeszów 35-310, Poland
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
3. Jagiellonian University, Institute of Physics (IF UJ), Reymonta 4, Kraków 30-059, Poland
4. Dipartimento di Fisica and Unita' INFM, Universita' di Roma "La Sapienza", Piazzale Aldo Moro 2, Roma 00185, Italy
5. °Laboratori Nazionali Frascati INFN (INFN), Via E. Fermi 40, Frascati 00044, Italy

Abstract

Far infrared reflectivity spectra of ZnxCd1-xTe (ZCT) alloys were measured in the expanded (in comparison with previous work [1]) composition range 0.056 to 0.75 using alternatively an infrared synchrotron radiation source and a mercury lamp. Spectra were measured on the FT IR-spectrometer (Bruker Equinox 55) available at the DAFNE-light facility of the INFN-LNF laboratory, with a resolution of 1 cm-1 for samples placed under vacuum in a helium cryostat for temperatures ranging from 20 K to 300 K. The measured spectra were analyzed by a standard Kramers-Kronig procedure to obtain the imaginary part of the dielectric functions. These were unfolded into their component Lorentzian oscillator sets. The unfolding is done using the statistical strained-tetrahedron model with its axioms as proposed by Robouch et al [1] with five-configuration distorted-tetrahedra, and extended to the analysis of far-IR spectra [2]. The unfolding reveals a fine structure with two overlapping bands, structures that had not been previously observed (see [3]). Each of the seven ZnxCd1-x Te samples upon analysis exhibits the expected eight spectral lines, each defined by its parameter triplet {Sk,Wk,Gk}. The unfolding yields the three site occupation preference (SOP) parameters {W1, W2, W3 =1}, revealing a distribution close to random {W1=W2=W3ş1}. Hence the real local crystalline structure of ZnxCd1-xTe is defined. Simultaneously the unfolding yields also deduced from the experiment oscillation strengths for CdTe and ZnTe, with values comparable to those available in literature for binary CdTe and ZnTe compounds. Our results are in good agreement with the proposed model of Ref. [3]. [1] -J. Polit, E.M. Sheregii, E. Ściesińska, J. Ściesiński, E. Burattini J. Konior, A. Kisiel A. Mycielski, Journal of Alloys and Compounds, 371, 172, 2004;[2]- B.V. Robouch, A. Kisiel and J. Konior, J. Alloys Compounds 339, 1 (2002.[3] B.V. Robouch, E.M. Sheregii, J.Polit, J.Cebulski sub to Phys.Rev.B
[ABSTRACT TRUNCATED TO 2000 LETTERS]

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Presentation: poster at E-MRS Fall Meeting 2004, Symposium F, by Jacek Polit
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-05-26 13:06
Revised:   2009-06-08 12:55
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