Nonsubstitutional single-atom defects in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Ge</mml:mtext></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Sn</mml:mtext></mml:mrow><mml:mi>x</mml:mi></mml:msub></mml:mrow></mml:math>alloy

Ventura, C. I.; Fuhr, J. D.; Barrio, Rafael A.

doi:10.1103/physrevb.79.155202

Cited by 18 publications

(37 citation statements)

References 39 publications

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“…Therefore, they would result in much shorter 1NN Sn-Ge distances than to the sum of Sn and Ge covalent radii-which were not observed. Similarly, the SV complexes predicted by Ventura et al 3 -which would have d SnGe ¼ 3.082 Å -were not observed. Hence, the SV complex configuration is not the most favorable one for Sn incorporation in these layers.…”

Section: A Sn Incorporation's Configuration In the Ge Latticementioning

confidence: 59%

“…In addition, such understanding could indicate the possible physical origin of the diverse properties observed in Ge 1Àx Sn x layers grown using various techniques, such as the thermal stability 1 or the types of electronic defects. 2 Theoretical analyses 3,4 and experimental Ge 1Àx Sn x growth/strain relaxation studies [5][6][7] suggest the formation of either a-Sn substitutional defects, fullvacancy (FV) structures, Sn interstitials, Sn pair-defects (SS), Sn-split vacancy complexes (SV), or 7-Sn clusterdefects (CD). In the a-Sn defects, the Sn atoms occupy substitutional sites in the Ge lattice; the same occurs in the SS and FV structures, but with another Sn atom or a Ge vacancy, respectively, as first neighbor.…”

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confidence: 99%

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Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Gencarelli

Grandjean

Shimura

et al. 2015

Journal of Applied Physics

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We present an extended X-ray absorption fine structure investigation of the local environment of Sn atoms in strained and relaxed Ge1−xSnx layers with different compositions. We show that the preferred configuration for the incorporation of Sn atoms in these Ge1−xSnx layers is that of a α-Sn defect, with each Sn atom covalently bonded to four Ge atoms in a classic tetrahedral configuration. Sn interstitials, Sn-split vacancy complexes, or Sn dimers, if present at all, are not expected to involve more than 2.5% of the total Sn atoms. This finding, along with a relative increase of Sn atoms in the second atomic shell around a central Sn atom in Ge1−xSnx layers with increasing Sn concentrations, suggests that the investigated materials are homogeneous random substitutional alloys. Within the accuracy of the measurements, the degree of strain relaxation of the Ge1−xSnx layers does not have a significant impact on the local atomic surrounding of the Sn atoms. Finally, the calculated topological rigidity parameter a** = 0.69 ± 0.29 indicates that the strain due to alloying in Ge1−xSnx is accommodated via bond stretching and bond bending, with a slight predominance of the latter, in agreement with ab initio calculations reported in literature.

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Section: A Sn Incorporation's Configuration In the Ge Latticementioning

confidence: 59%

mentioning

confidence: 99%

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Gencarelli

Grandjean

Shimura

et al. 2015

Journal of Applied Physics

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“…Moreover, calculations of the hyperfine parameters of this defect indicate that it has probably been present in Mössbauer experiments before, without having been identified as such. In our work, we have presented strong evidence, both experimentally and theoretically, that the Sn-vacancy defect prefers the split-vacancy configuration which is thermally stable up to 400 ∘ C. This result is of major importance in the understanding of the problems that arise in the formation of diluted Sn x Ge 1−x alloys, since recent calculations have indicated that the split-vacancy configuration of the Sn atom in Ge is a nucleation point of metallic Sn 33 , hence deteriorating the semiconducting properties. Besides this, our results contribute to the study of simple point defects in elemental group IV semiconductors and are important to understand the vacancymediated mechanism of Sn diffusion -and maybe even self-diffusion -in germanium.…”

Section: Discussionmentioning

confidence: 74%

Lattice location study of ion implanted Sn and Sn-related defects in Ge

Decoster

Cottenier

Wahl³

et al. 2010

Phys. Rev. B

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In this work, we present a lattice location study of Sn in Ge. From emission channeling experiments, we determined the exact lattice location of ion implanted 121 Sn atoms, and compared the results to predictions from density functional calculations. The majority of the Sn atoms are positioned on the substitutional site, as can be expected for an isovalent impurity, while a second significant fraction occupies the six-fold coordinated bond-centered site. Corroborated by ab initio calculations, we attribute this fraction of bond-centered Sn atoms to the Sn-vacancy defect complex in the split-vacancy configuration. Furthermore, we are able to assign specific defect complex geometries to resonances from earlier Mössbauer spectroscopy studies of Sn in Ge.

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“…Using the data provided in Figure 1 and Yet another interpretation of the discrepancy between theory and experiment would consist in assuming that the observed deviation from Vegard's law is caused by the combined effects of a positive contribution, as calculated for a perfectly random alloy, plus a negative term associated with a non-random atomic distribution and/or defects. This is suggested by the observation that the ratio η GeSn = θ 37 we estimate that about 6% of the Sn atoms in the alloy should be in split vacancy locations to explain the difference between the observed and predicted lattice parameter for y = 0.06. This is a much higher concentration of split vacancies than predicted by these authors, and constitutes a level of nonsubstitutionality that likely would have been detected in our XRD or RBS channeling experiments.…”

Section: Discussionmentioning

confidence: 92%

Nonlinear structure-composition relationships in the Ge1−ySny/Si(100) (y<<

et al. 2011

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The compositional dependence of the cubic lattice parameter in Ge 1-y Sn y alloys has been revisited. Large 1000-atom supercell ab initio simulations confirm earlier theoretical predictions that indicate a positive quadratic deviation from Vegards' law, albeit with a somewhat smaller bowing coefficient, θ = 0.047 Å, than found from 64-atom cell simulations (θ = 0.063 Å). On the other hand, measurements from an extensive set of alloy samples with compositions y < 0.15 reveal a negative deviation from Vegard's law. The discrepancy with earlier experimental data, which supported the theoretical results, is traced back to an unexpected compositional dependence of the residual strain after growth on Si substrates. The experimental bowing parameter for the relaxed lattice constant of the alloys is found to be θ = -0.066 Å. Possible reasons for the disagreement between theory and experiment are discussed in detail.

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Nonsubstitutional single-atom defects in theGe1−xSnxalloy

Cited by 18 publications

References 39 publications

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Extended X-ray absorption fine structure investigation of Sn local environment in strained and relaxed epitaxial Ge1−xSnx films

Lattice location study of ion implanted Sn and Sn-related defects in Ge

Nonlinear structure-composition relationships in the Ge1−ySny/Si(100) (y<<

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