DAFS - Universidad de Zaragoza
DAFS - Universidad de Zaragoza DAFS - Universidad de Zaragoza
Conclusiones Medidas a RT Fe2+ Fe3+ e τhopping >> τRayos-X ≈ 10-15 El DAFS nos proporciona por primera vez evidencia DIRECTA sobre el estado electrónico del Fe. El DAFS de las reflexiones prohibidas se interpreta perfectamente en el esquema de la anisotropía del f (ATS) Los sitios del Fe octaédrico, considerados tradicionalmente fluctuantes entre dos estados de valencia Fe2+ y Fe3+, son electronicamente IDENTICOS s No hay fluctuación de carga para T>Tc Medidas a baja T Misma dependencia en E y en f para T
Grazing Incidence Diffraction Anomalous Fine Structure (GIDAFS) 1) 2D FEM similations to fit the anomalous diffraction data, including DAFS line shape (β, ∆φ), can give the true structure : shape, size strain and composition ε xx ε zz Simulation of As 1-x P x composition in the wires lead to x ~ 0 Chemical composition ? Diffraction Intensity Intensity (a.u.) Tedious task, not always successful ! 80 70 60 50 40 30 2) Energy scan, fixed Q : max. of F A (h=k=3.98, l=1.9) Diffraction selected local structure : • lattice strain accomodation • composition 11,7 11,8 11,9 12 Energy (keV) E(keV) As K-edge BM2, ESRF
- Page 1 and 2: Universidad de Zaragoza Curso de Ma
- Page 3 and 4: TÉCNICAS EXPERIMENTALES µ I diff
- Page 5 and 6: EL DAFS El DAFS es la estructura fi
- Page 7 and 8: Resonant atomic scattering factor f
- Page 9 and 10: y 0 Structure factor: Multi-wavelen
- Page 11 and 12: I F diff 0 F 0 Análisis de datos D
- Page 13 and 14: Using the path formalism for descri
- Page 15 and 16: Spatial selectivity : GaAs xP 1-x/G
- Page 17 and 18: TEM InAs/InP QWrs AFM 200nm GaN/AlN
- Page 19 and 20: Local structure study of InAs/InP Q
- Page 21 and 22: As-O As K-edge EXAFS (BM8-ESRF) Int
- Page 23 and 24: Grazing incidence diffraction BM2-D
- Page 25 and 26: GI-DAFS (Grazing Incidence DAFS) k(
- Page 27 and 28: Diffraction Intensity (a.u.) GIDAFS
- Page 29 and 30: Abs II EXAFS and EDAFS best fit res
- Page 31 and 32: GIDAFS oscillations analysis CP1276
- Page 33 and 34: EXAFS (ε // & ε ⊥) Similar resu
- Page 35 and 36: Applications : Nanostructures III-V
- Page 37 and 38: Applications : Nanostructures III-V
- Page 39 and 40: BQ GaN/AlN 10ML : EXAFS vs DAFS k
- Page 41 and 42: BQ GaN/AlN : EDAFS simulations h=2.
- Page 43 and 44: Orden de carga y reflexiones prohib
- Page 45 and 46: Estado electrónico de los sitios o
- Page 47 and 48: Anisotropía del factor de dispersi
- Page 49 and 50: Zona del umbral (DANES) Modelo refl
- Page 51: Prepico Cálculos “ab initio” d
Grazing Inci<strong>de</strong>nce Diffraction Anomalous Fine Structure (GI<strong>DAFS</strong>)<br />
1) 2D FEM similations to fit<br />
the anomalous diffraction<br />
data, including <strong>DAFS</strong> line<br />
shape (β, ∆φ), can give the<br />
true structure : shape,<br />
size strain and composition<br />
ε xx<br />
ε zz<br />
Simulation of As 1-x P x composition<br />
in the wires lead to x ~ 0<br />
Chemical composition ?<br />
Diffraction Intensity Intensity (a.u.)<br />
Tedious task, not always successful !<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
2) Energy scan, fixed Q : max.<br />
of F A (h=k=3.98, l=1.9)<br />
Diffraction selected local structure :<br />
• lattice strain accomodation<br />
• composition<br />
11,7 11,8 11,9 12<br />
Energy (keV)<br />
E(keV)<br />
As K-edge BM2, ESRF
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