Negative Thermal Expansion in Zincblende Structure: an EXAFS study of CdTe

Abd El All, Naglaa Fathy (2010) Negative Thermal Expansion in Zincblende Structure: an EXAFS study of CdTe. PhD thesis, University of Trento.

PDF - Doctoral Thesis


To gain a deeper insight on the local origin of NTE in zincblende crystals, EXAFS measurements have been performed on CdTe, which has NTE properties intermediate between Ge and CuCl. In this work an accurate evaluation of the bond thermal expansion, parallel and perpendicular MSRDs and distribution asymmetry of the first shell of CdTe has been made, obtaining a good agreement between two different procedures of the data analysis (i) ratio method (ii) FEFF6-FEFFIT method. The values of the relevant parameters of CdTe were found intermediate between the corresponding values previously found for Ge and CuCl. The positive contribution to thermal expansion due to the bond stretching and the negative contribution due to the tension effects are disentangled and quatified in terms of the bond thermal expansion and the perpendicular MSRD, respectively, determined by the EXAFS analysis. A critical comparison of EXAFS and Bragg diffraction results; thermal expansion, thermal factors and correlation of atomic vibration, for the iso-structural crystals Ge, CdTe and CuCl has been performed. The correlation between several quantities measured by EXAFS and NTE properties is confirmed.

Item Type:Doctoral Thesis (PhD)
Doctoral School:Physics
Subjects:Area 02 - Scienze fisiche > FIS/01 FISICA SPERIMENTALE
Area 02 - Scienze fisiche > FIS/03 FISICA DELLA MATERIA
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