Local atomic structure of semiconductor alloys using pair distribution functions

Chung, Jean S.; Thorpe, M. F.

doi:10.1103/physrevb.55.1545

Cited by 50 publications

(52 citation statements)

References 16 publications

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“…Our reported values of ρ B−B , ρ B−Mg ∼ 0.1 are however much smaller than the correlation factors commonly found in other covalently bonded materials. [33,29,31,32] This observation points out once more that all the motions are decoupled and the atoms are behaving largely like independent oscillators.…”

Section: Correlations In the B-b And B-mg Atomic Pairs Motionmentioning

confidence: 86%

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Study of temperature dependent atomic correlations in MgB2

et al. 2006

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Abstract. We have studied the evolution with temperature of the local as well as the average crystal structure of MgB2 using the real-space atomic pair distribution function (PDF) measured by high resolution neutron powder diffraction. We have investigated the correlations of the B-B and B-Mg nearest neighbor pair motion by comparing, in the wide temperature range from T = 10 K up to T = 600 K, the meansquare displacements (MSD) of single atoms with the mean-square relative displacements (MSRD) obtained from the PDF peak linewidths. The results show that the single atom B and Mg vibrations are mostly decoupled from each other, with a small predominance of positive (in phase) correlation factor for both the B-B and B-Mg pairs. The small positive correlation is almost temperature independent, in contrast with our theoretical calculations; this can be a direct consequence of the strong decay processes of the E2g anharmonic phonons.PACS. 74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.) -61.12.-q Neutron diffraction and scattering -63.20.-e Phonons in crystal lattices

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Section: Correlations In the B-b And B-mg Atomic Pairs Motionmentioning

confidence: 86%

“…It is now useful to quantify the degree of correlation by introducing the dimensionless correlation parameter ρ ij defined as: [33,29,31,32]…”

Section: Correlations In the B-b And B-mg Atomic Pairs Motionmentioning

confidence: 99%

Study of temperature dependent atomic correlations in MgB2

et al. 2006

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“…Within the harmonic approximation, the mean square relative displacement (MSRD) of the two atoms depends on the eigenvalues and eigenvectors of dynamical matrix through the integral over all normal modes [55]. However, the contribution of each normal mode is inversely proportional to the square of its frequency.…”

Section: Md-exafs Simulationsmentioning

confidence: 99%

Temperature dependence of the local structure and lattice dynamics of wurtzite-type ZnO

et al. 2014

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Temperature-dependent (10-300 K) Zn K-edge EXAFS spectra for polycrystalline wurtzite-type ZnO were analysed using ab initio multiple-scattering theory and taking into account anisotropy of the crystallographic structure and thermal disorder. We employed two different simulation approaches: classical molecular dynamics (MD) and reverse Monte Carlo coupled with evolutionary algorithm (RMC/EA method). The accuracy of several forcefield models, which are commonly used in the MD simulations of bulk and nanostructured ZnO, was tested based on a comparison between the experimental and simulated Zn K-edge EXAFS spectra. It was found that available force-field models fail to describe accurately many-atom distribution functions. More accurate solution was obtained by the RMC/EA method, which allowed us also to resolve the non-equivalent groups of atoms in the first two coordination shells around absorbing Zn atom and to follow the changes of structural parameters with temperature variation. It was found that upon increasing temperature the structure of ZnO becomes more anisotropic due to the increase of internal parameter u of the oxygen Wyckoff position (2b) and related Zn 0 -O 2 distances.

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“…From this the Debye-Waller factors for all the individual atoms in the supercell can be found and hence the PDF of the model by including the Gaussian broadening of all the subpeaks. We have shown previously [15] that this is the correct procedure within the harmonic approximation. The model-PDF is plotted with the data in the inset to Fig.…”

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confidence: 99%

High Real-Space Resolution Measurement of the Local Structure ofGa1−xInxAsUsi

et al. 1999

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High real-space resolution atomic pair distribution functions (PDF)s from the alloy series Ga1−xInxAs have been obtained using high-energy x-ray diffraction. The first peak in the PDF is resolved as a doublet due to the presence of two nearest neighbor bond lengths, Ga-As and In-As, as previously observed using XAFS. The widths of nearest, and higher, neighbor pairs are analyzed by separating the strain broadening from the thermal motion. The strain broadening is five times larger for distant atomic neighbors as compared to nearest neighbors. The results are in agreement with model calculations.The average atomic arrangement of crystalline semiconductor alloys is usually obtained from the position and intensities of the Bragg peaks in a diffraction experiment [1], and the actual nearest neighbor and sometimes next nearest neighbor distances for various pairs of atoms by XAFS measurements [2]. In this Letter we show how high energy x-ray diffraction and the resulting highresolution atomic pair distribution functions (PDF)s can be used for studying the internal strain in Ga 1−x In x As alloys. We show that the first peak in the PDFs can be resolved as a doublet and, hence, the mean position and also the widths of the Ga-As and In-As bond length distributions determined. The detailed structure in the PDF can be followed out to very large distances and the widths of the various peaks obtained. We use the concentration dependence of the peak widths to separate the strain broadening from the thermal broadening. At large distances the strain broadening is shown to be about five times larger than for nearest neighbor pairs. Using a simple valence force field model, we get good agreement with the experimental results.

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Local atomic structure of semiconductor alloys using pair distribution functions

Cited by 50 publications

References 16 publications

Study of temperature dependent atomic correlations in MgB2

Study of temperature dependent atomic correlations in MgB2

Temperature dependence of the local structure and lattice dynamics of wurtzite-type ZnO

High Real-Space Resolution Measurement of the Local Structure ofGa1−xInxAsUsi

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