Transcription of XAFSの基礎理論 - KEK
1 XAFS XAFS 1 OutlineXAFS X X (XAFS)EXAFS XAFS 2 XAFS 3101001000100001000000102030405060708090 100ZE/eVKL-IL-IIL-IIIM-IM-IIM-IIIM-IVM-V KLMNeCaZZrSnNdYbHgThTi5keVCsBa X X XAFS 4 AdvantageNoteXAFS XAFS 5 XRD X X X XPS X 10-13secRaman 10-13sec
2 NMR EPR 10-10secXAFS X X 10-16sec6X 7 X XRDXAFS8 XPS X 9X (X-ray Absorption Fine Structure) xanes (X EXAFS( XAFS)10 EXAFS BL9A Foil II0 t= ln I0/I t 25~300 K He 300~1000 K 111s2s2pVacuum levelEXAFS xanes X X 700075008000012 Photon Energy / eVAbsorption intensityEXAFSXANES EoEo12 xanes Cr(III) Cr(VI) [Cr6+O4] [Cr3+(OH2)6]3+1314 xanes (Cr )XANESTi V 151s eg, t2g V(IV)V(III)V(II)Ti16 (MnMoV6)MnVMoX-ray 1s2s2pVacuum levelX EXAFS Extended X-ray absorption fine structure17 18 19 EXAFS CdTe et al.)
3 , 199820 EXAFS 21X 70007500800001 Photon Energy / eVAbsorption intensity0prepost0)(sk postpres 20/2 EEmk kE0221s2s2pmkEE2220 EXAFS (k) / -1k(k) )(2sin),()()(222220kkrekfkrSNkiiikrkiiii i 23 /|FT|1st2nd2nd2nd3rd4th1st2nd3rd4th 24 EXAFS )(2sin),()()(222220kkrekfkrSNkiiikrkiiii i Ni: i ri: i i: Debye-Waller f k, : i k : i k : i FEFF 9 by , UW 25 26f k, i k |FT| |FT|50K150K250K350K470K FeRh 1st2nd2nd2ndX 1st Rh-Fe2nd Rh-RhFeK-edgeRhK-edge1st Fe-Rh2nd Fe-Fe27 Debye-Waller 222ST T: DW S DW : 10-16sec 10-13sec28 Einstein DW)20)(21)(rrMrVE TkBET2coth202 / K2/22nd Fe-Fe1st Fe-Fe DW Einstein (1)(2) E Einstein 29 EXAFS xanes xanes 1)3 2) 3) EXAFS 1) 1 2) 3) R: , N.
4 10%4) 30 XAFSS ummary31 XAFS EXAFSXANESXAFS= xanes +EXAFS XAFS xanes EXAFS XMCD XAFS 32 PbTiO3 CubicTetragonalXANES XRD 33 / eV(E) (1s 3d)Peak APeak ATi K-edge XANES34 / Karea of peak / Kd (Ti displacement) / , , , , Recent Research Developments in Physics,, 3, Part II, 641-657 (2002).XANES35 XRD XAFS XRD X XAFS 36 Single-Quantum-Well LEDInxGa1-xN LEDC hichibu, , Sota, T.
5 , Wada, K., Brandt, O., Ploog, , DenBaars, , and Nakamura, S., Phys. Stat. Sol.(a),183, 91 (2001).37 ExperimentalSamples:The sample was grown by MOCVD3nm SQWInxGa1-xN (x = blue, green, amber)SampleStructure of InGaN SQW (3nm) In N Ga or / / keVVerticaltXAS of SQW39 EXAFS k (k) spectra and Fourier transform of In K-edge for SQW in horizontal and vertical / k(k) /-1 Horizontal / |FT(r)| / Horizontal VerticalIn-NIn-Ga/In40 / |FT(r)| / Exp. Fit (In-N) Fit (In-Ga/In)41 Result 1 Interatomic distance(1)In-N:Horizontal ~Vertical ( )(2)In-Ga/In: Vertical ( ) >Horizontal ( ) SQW is biaxially compressed in a-bplane42 Result 2(1)Horizontal: In atoms are randomly distributed(2)Vertical: In atoms are aggregated and located top and bottomIn mole fluctuation !
6 43 ConclusionEXAFS result is evidence of composition fluctuation of In atomin the SQW and should closely related to the high quantum efficiencyof InGaN Te |FT(r)|r |FT(r)|r et al., XAFS 14 confernece45 XAFSX 2 XMCD) X X X 46 XMCD for Fe LII,IIIedges47 et al., SRN, 10, 6 (1997).48 XAFS 1) 2) 3) 4) XAFS XAFS 1) 2) X 3) XAFS 4) XAFS 49 XAFS XAFS XAFS 100 30 XAFS 50
