First-shell bond lengths inSixGe1−xcrystalline alloys

Abstract

Si and Ge K-edge x-ray absorption fine structure ͑XAFS͒ spectra of strained and relaxed Si x Ge 1Ϫx crystalline alloys grown by molecular beam epitaxy on Si͑001͒ substrates are reported. For alloys with less than 30% Si, fluorescence yield detection is shown to be essential to avoid distortions of the Si K-edge XAFS signal caused by the underlying Ge L-edge XAFS signal from the majority Ge species. The average first shell structure has been deduced using simultaneous fitting of all data for relaxed alloys, while imposing physically reasonable constraints. The Ge-Ge, Ge-Si, and Si-Si first-shell distances are found to vary with composition. The results are compared with other experimental results and theoretical predictions in the literature. Our results are generally consistent with other experimental studies but they differ from recent theoretical predictions based on macroscopic elastic properties in that we observe a different compositional dependence ͓i.e.,

Nonlinear stability ofEcenters inSi1−xGex: Electronic structure calculations

“…We predict that E centers have greater binding energies when more Ge atoms are at first-nearest-neighbor sites around the V. This is a consequence of the weaker and less stiff Ge-Ge bonds compared to the Si-Si bonds. 54 For example, in Fig. 2 we plot the binding enthalpy of the E centers considered as a function of Ge atoms at a first-nearest-neighbor site with respect to the V in Si 0.5 Ge 0.5 .…”

EXAFS study on poly-Si1−XGeX films prepared by reactive thermal CVD method

“…In the present study, in order to compare the data to the results of previous studies [7,8], the Ge coordination ratio, X c = N G /(N G + N S ) [11], was …”

“…Ge K-edge EXAFS analyses were carried out on several Si 1ÀX Ge X films of different thicknesses fabricated using an identical deposition condition. Structural changes during the deposition, as well as the structural features of the reactive thermal CVD Si 1ÀX Ge X , are discussed compared to previous EXAFS studies [7][8][9][10] on this alloy system.…”

Isovalent impurity‐vacancy complexes in germanium

“…It should be stressed that the binding of the two V is attributed to the reduction of the dangling bonds from 8 (in the case of two isolated vacancies) to 6 for a V-V pair. The V-V pair is more stable in Si than in Ge highlighting the stiffer Si-Si bonds compared to the weaker Ge-Ge bonds [22].…”