X-ray-absorption fine-structure study of ZnSexTe1−x alloys

Abstract

X-ray-absorption fine-structure experiments at different temperatures in ZnSe x Te 1−x (x = 0, 0.1, 0.2, 0.55, 0.81, 0.93, 0.99, and 1.0) have been performed in order to obtain information about the structural relaxation and disorder effects occurring in the alloys. First and second neighbor distance distributions have been characterized at the Se and Zn K edges, using multiple-edge and multiple-scattering data analysis. The first neighbor distance distribution was found to be bimodal. The static disorder associated with the Zn-Te distance variance did not depend appreciably on composition. On the other hand, the static disorder associated with the Zn-Se distance increased as the Se content diminished. Using the bonding angle information provided by our experiments the point of view of the anion has been related to that of the cation. The resulting structural model indicates that Zn tetrahedra surrounding the anions remain essentially undistorted, but forced to tilt from their ideal zincblende orientation to accommodate the minority element. The main origin of structural disorder is suggested.

Unification of the phonon mode behavior in semiconductor alloys: Theory andab initiocalculations

“…The ω imp values were derived by relying on thorough EXAFS measurements of bond length in ZnTeSe. 22 The shift ∆ω 2 T in the square TO frequency of an impurity mode with respect to the corresponding TO mode in the pure crystal was inferred from the related difference in bond length ∆l via the TO mode Grüneisen parameter γ T of the pure crystal, by using the simple relation…”

An EXAFS study of the structure of the Zn1-xBexSe alloy system

“…the shear modulus of BeSe is 42. 6 GPa as compared to 18.35 GPa for ZnSe [2]. Besides its technological importance, the Raman data of this material system shows a novel and atypical three mode behavior, ie, a single mode for Zn-Se bond and a two-mode behavior for the Be-Se bond [3] in complete contradiction to the Modified Random Element Isodisplacement (MREI) model [3].…”

“…We have also evaluated the next nearest neighbor (NNN) bond lengths to have a detailed understanding of the atomic arrangement in this ternary compound. Although the EXAFS data of Zn 1-x [6],GaAs x P 1-x [7] and In x Ga 1-x As [8]. Finally, the quantitative differences in the EXAFS data of this material system and other previously studied ternary systems have been examined in detail in this work.…”

Thermal instability of electrically active centers in heavily Ga-doped ZnO thin films: X-ray absorption study of the Ga-site configuration

“…The EXAFS fit ͑Table I͒ has been performed introducing phases and amplitudes calculated with FEFF8 using a self-consistent potential. In 19,20 that the cation-anion first neighbor distance in A 1−x B x C zincblende random alloys remains near to that of the end compounds. Given the similarities in bonding between zincblende and wurtzite, an analogous situation could be imagined in Zn 0.96 Ga 0.04 O, where the Ga-O distance would remain near to the tetrahedral bonding distance in ␤-Ga 2 O 3 .…”