DAFS - Universidad de Zaragoza

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$Difracción de Rayos X, neutrones y electrones$

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

DAFS - Universidad de Zaragoza

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