VIII° Scuola Nazionale Luce di Sincrotrone Laboratori Nazionali di Frascati 10-21 ottobre 2005 Esercitazione pratica di diffrazione di fotoelettroni A.Verdini, A. Morgante Laboratorio TASC, CNR-INFM c/o Area Science Park S.S. 14, km 163.5, Basovizza – 34012 Trieste email: [email protected], [email protected]
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VIII° Scuola Nazionale Luce di Sincrotrone Laboratori Nazionali di Frascati 10-21 ottobre 2005
Esercitazione pratica di diffrazione di fotoelettroni
A.Verdini, A. MorganteLaboratorio TASC, CNR-INFM
c/o Area Science ParkS.S. 14, km 163.5, Basovizza – 34012 Trieste
<< Larghezza del picco Lorentziana o Doniach-Sunjic
~ Larghezza del picco Convoluzione
>> Larghezza del picco GaussianaS. Hufner, G.K. Wertheim, PRB 11, p 678 (1975)
Esempio: Ferro depositato su Cu3Au(100)
• Crescita pseudomorfa• Struttura di un cristallo face-centered-cubic - fcc
Fe
Cu3Au
Spettro di fotoemissione
15x103
10
5
0
Inte
nsity
(cou
nts/
s)
900800700600500400300200100Kinetic Energy (eV)
Fe 2p Fe Auger Cu Auger
Au 4d
Au 4f
1000
800
600
400
200
Inte
nsity
(arb
. uni
ts)
240230220210200Kinetic Energy (eV)
Scansione polare
normale45º45º
2.0
1.5
1.0
0.5
0.0
-0.5
Inte
nsita
' (un
ita' a
rb.)
9080706050403020100-10Bimodale (°)
Normale
<100>
La anisotropia χcontiene informazioni relative alla diffrazione
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
anis
otro
pia χ
90 80 70 60 50 40 30 20 10 0Angolo polare (º)
0
0
III −
=χ
Come si calcola la χ
La I0 si ottiene come fit dei dati un polinomio
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
-80 -60 -40 -20 0 20 40 60 80
Dati Fit χ
0
0
III −
=χ
Simulazioni
• pacchetto mscd– download gratuito: electron.lbl.gov– scattering multiplo– formalismo di Rehr-Albers– cluster fino a 300 atomi
Un file di input741 10 92 datakind begining-row linenumbers----------------------------------------------------------------MSCD Version 1.00 Yufeng Chen and Michel A Van HoveLawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720Copyright (c) Van Hove Group 1997. All rights reserved----------------------------------------------------------------
Cu3Au(001)+Fe- Input file
un "A. Verdini" user namesn Cu3Au(001)+fe system nameps01 psau.txt input phase shift data fileps02 pscu.txt input phase shift data fileps03 psfe.txt input phase shift data filerm rmfe2p.txt input radial matrix data filepe 3fe_a1_1875_a2_1875.txt output photo emission data file
1 3 1 0 layer, kind, emitter, lineatom0 0 0 0 latoms(xa,xb,ya,yb)0.7071068 -45.000000 unita(len ang) (fcc (100) structure)0.7071068 45.000000 unitb(len ang) (in unit of lattice)0.5000000 0.0000000 origin(len ang) (in unit of lattice)0.2500000 interlayer spacing (unit lattice)0.0 0.0 0.0 fit try for spacing, length and units
2 3 1 0 layer, kind, emitter, lineatom0 0 0 0 latoms(xa,xb,ya,yb)0.7071068 -45.000000 unita(len ang) (fcc (100) structure)0.7071068 45.000000 unitb(len ang) (in unit of lattice)0.0000000 0.0000000 origin(len ang) (in unit of lattice)0.5000000 interlayer spacing (unit lattice)0.0 0.0 0.0 fit try for spacing, length and units
3 3 1 0 layer, kind, emitter, lineatom0 0 0 0 latoms(xa,xb,ya,yb)0.7071068 -45.000000 unita(len ang) (fcc (100) structure)0.7071068 45.000000 unitb(len ang) (in unit of lattice)0.5000000 0.0000000 origin(len ang) (in unit of lattice)0.5000000 interlayer spacing (unit lattice)0.0 0.0 0.0 fit try for spacing, length and units.
4 2 0 0 layer, kind, emitter, lineatom0 0 0 0 latoms(xa,xb,ya,yb)1.0000000 0.000000 unita(len ang) (fcc (100) structure)1.0000000 90.000000 unitb(len ang) (in unit of lattice)0.0000000 0.0000000 origin(len ang) (in unit of lattice)0.5000000 interlayer spacing (unit lattice)0.0 0.0 0.0 fit try for spacing, length and units
5 1 0 0 layer, kind, emitter, lineatom0 0 0 0 latoms(xa,xb,ya,yb)1.0000000 0.000000 unita(len ang) (fcc (100) structure)1.0000000 90.000000 unitb(len ang) (in unit of lattice)0.7071068 45.000000 origin(len ang) (in unit of lattice)0.0000000 interlayer spacing (unit lattice)0.0 0.0 0.0 fit try for spacing, length and units
6 2 0 0 layer, kind, emitter, lineatom0 0 0 0 latoms(xa,xb,ya,yb)0.7071068 -45.000000 unita(len ang) (fcc (100) structure)0.7071068 45.000000 unitb(len ang) (in unit of lattice)0.5000000 0.0000000 origin(len ang) (in unit of lattice)0.5000000 interlayer spacing (unit lattice)0.0 0.0 0.0 fit try for spacing, length and unit
Il file di input
• file esterni che servono– shift di fase “ps” per le diverse specie– matrici radiali dell’emettitore
• nome del file di output• l’energia cinetica in Å-1
112 28 87 datakind beginning-row linenumbers-----------------------------------------------------------------Calculation of photoelectron diffraction and dichroismMSCD Version 1.37 Yufeng Chen and Michel A Van HoveLawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720Copyright (c) Van Hove Group 1997-1998. All rights reserved-----------------------------------------------------------------angle-resolved photoemission extended fine structure (ARPEFS)multiple scattering calculation of Cu3Au(001)+fecalculated by A. Verdini on Oct 03, 2005