Investigation of indirect structural and chemical parameters of GeSi nanoparticles in a silica matrix by combined synchrotron radiation techniques

Abstract

The formation of GeSi nanoparticles on an SiO 2 matrix is studied here by synchrotron-based techniques. The shape, average diameter and size dispersion were obtained from grazing-incidence small-angle X-ray scattering data. X-ray diffraction measurements were used to obtain crystallite sizes and composition via resonant (anomalous) measurements. By using these techniques as input for extended X-ray absorption fine structure analysis, the local composition surrounding the Ge atoms is investigated. Although the results for each of the methods above are commonly analyzed separately, the combination of such techniques leads to an improved understanding of nanoparticle structural and chemical properties. Crucial indirect parameters that cannot be quantified by other means are accessed in this work, such as local strain, the possibility of forming core-shell structures, the fraction of Ge atoms diluted in the matrix (not forming nanoparticles), the amorphous and crystalline Ge fractions, and the relative population of nanoparticles with single and multiple crystalline domains.

Evidence for the formation of SiGe nanoparticles in Ge-implanted Si3N4

“…26 The refined fitting parameters for the NP FNN shells are listed in Table I. The results from previous studies 19,30,31 are also listed in Table I for reference. The changes in the structural parameters are consistent with the qualitative description described above, with the formation of a combination of amorphous and crystalline phases.…”

“…Structural parameters-interatomic distance R, Debye-Waller factors r 2 , and coordination numbers CN-obtained for the FNN of NPs. Total CN increases with an increase in temperature.Ref 31. SiGe NPs embedded in the SiO 2 matrix (the total coordination number is fixed to 3.77).…”

New approach for structural characterization of planar sets of nanoparticles embedded into a solid matrix

“…The NPs are thermodynamically unstable and lead to the formation of a solute concentration field of their constituent atoms dissolved within the surrounding matrix as provided, for example, by the Gibbs-Thomson effect 7 . For Ge NPs in silica, empirical evidence shows that a significantly high fraction of the total Ge content in the sample (from 20 to 70%) may remain dissolved in the matrix even after high temperature thermal treatments 8 9 10 . In this case it is argued that, since Ge and Si behave similarly with respect to the formation of tetrahedral bonding structures, Ge atoms could indeed replace Si ones in the SiO 2 lattice and therefore present a high solubility limit.…”