Intro to XPS and UPS Helmholtz

Introduction into X-ray
and UV Photoelectron
Spectroscopy
(XPS/UPS)
Introduction to X-ray and UV
Photoelectron Spectroscopy (XPS/UPS)
What is XPS?
How can we identify elements and compounds?
What is UPS?
What is a work function(Φ)?
Examples of investigations using ∆Φ/UPS/XPS/HIKE
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
What is XPS?
X-ray Photoelectron Spectroscopy (XPS), also known as
Electron Spectroscopy for Chemical Analysis (ESCA) is a
widely used technique to investigate the chemical
composition of surfaces
surfaces..
X-ray Photoelectron spectroscopy, based on the photoelectric
effect,1,2 was developed in the midmid-1960’s by Kai Siegbahn
and his research group at the University of Uppsala, Sweden.3
1. H. Hertz, Ann. Physik 31,983 (1887).
2. A. Einstein, Ann. Physik 17,132 (1905). 1921 Nobel Prize in Physics.
3. K. Siegbahn, et. al., Nova Acta Regiae Soc.Sci., Ser. IV, Vol. 20 (1967). 1981 Nobel Prize in Physics.
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Au(111)
Au 4f
6
6
1,5x10
6
1,0x10
Au NVV
5
5,0x10
Au 5p
Au 4d
VB
0,0
100
200
300
400
500
600
Ekin [eV]
Au(111)
Au 4f
2,0x10
intensity [arb.u]
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
The Photoelectric Process
Conduction Band
Free
Electron
Level
Fermi
Level
Valence Band
2p
L2,L3
2s
L1
1s
K
XPS spectral lines are
identified by the shell from
which the electron was
ejected (1s, 2s, 2p, etc.).
The ejected photoelectron has
kinetic energy:
KE=hv--BE
KE=hv
BE--Φ
Following this process, the
atom will release energy by
the emission of an Auger
Electron.
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Incident XX-ray
Ejected Photoelectron
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Auger Relation of Core Hole
Emitted Auger Electron
Valence Band
2p
L2,L3
2s
L1
1s
K
L electron falls to fill core level
vacancy (step 1).
KLL Auger electron emitted to
conserve energy released in
step 1.
The kinetic energy of the
emitted Auger electron is:
KE=E(K)--E(L2)KE=E(K)
E(L2)-E(L3).
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Conduction Band
Free
Electron
Level
Fermi
Level
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Relative Probabilities of Relaxation of
a K Shell Core Hole
1.0
0.6
0.4
0.2
Note: The light
elements have a
low cross section
for XX-ray emission.
X-ray Photon
Emission
0
5 10 15 20 25 30 35 40 Atomic Number
B Ne P Ca Mn Zn Br Zr
Elemental Symbol
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Probability
0.8
Auger Electron
Emission
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
XPS Energy Scale
The XPS instrument measures the kinetic
energy of all collected electrons. The
electron signal includes contributions from
both photoelectron and Auger electron lines.
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
5
Cu(111)
1.5x10
xx0287_1
intensity [arb.u.]
Au(111)
Au 4f
6
6
1,5x10
4
5.0x10
0.0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Ekin [eV]
5
3.0x10
6
1,0x10
Cu(111)
2.5x10
Au NVV
5
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
5
2.0x10
5
1.5x10
5
1.0x10
600
4
5.0x10
0.0
100
200
300
400
500
600
Ekin [eV]
Au(111)
Au 4f
2,0x10
intensity [arb.u]
5,0x10
xx0291_1
2nd order!!
5
intensity [arb.u.]
intensity [arb.u]
2,0x10
5
1.0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Sample/Spectrometer Energy Level DiagramConducting Sample
e-
Sample
Spectrometer
Free Electron Energy
Vacuum Level, Ev
hv
KE(1s)
KE(1s)
Φsample
Φspec
Fermi Level, Ef
BE(1s)
E1s
Because the Fermi levels of the sample and spectrometer are aligned, we only need
to know the spectrometer work function, Φspec, to calculate BE(1s).
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
XPS Energy Scale - Kinetic energy
KE = hv - BE - Φspec
Where: BE
BE=
= Electron Binding Energy
KE
KE=
= Electron Kinetic Energy
Φspec= Spectrometer Work Function
Photoelectron line energies: Dependent on photon energy.
Auger electron line energies: Not Dependent on photon energy.
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
XPS Energy Scale- Binding energy
BE = hv - KE - Φspec
Where: BE
BE=
= Electron Binding Energy
KE
KE=
= Electron Kinetic Energy
Φspec= Spectrometer Work Function
Photoelectron line energies: Not Dependent on photon energy.
Auger electron line energies: Dependent on photon energy.
The binding energy scale was derived to make uniform
comparisons of chemical states straight forward.
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Fermi Level Referencing
Free electrons (those giving rise to conductivity) find
an equal potential which is constant throughout the material.
Fermi--Dirac Statistics:
Fermi
T=0 K
kT<<Ef
f(E)
f(E) =
1
exp[(E--Ef)/kT] + 1
exp[(E
1.0
0.5
0
1. At T=0 K:
f(E)=1 for E<Ef
f(E)=0 for E>Ef
Ef
2. At kT<<Ef (at room temperature kT=0.025 eV)
f(E)=0.5 for E=Ef
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Elemental Shifts
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Where do Binding Energy Shifts Come From?
-or How Can We Identify Elements and Compounds?
Fermi Level
Pure Element
Electron-electron
Electronrepulsion
Electron
Electron-nucleus
Electronattraction
Binding
Energy
Look for changes
here by observing
electron binding
energies
ElectronElectronNucleus
Separation
Nucleus
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Elemental Shifts
Binding Energy (eV)
Element
2p3/2
3p
∆
Fe
707
53
654
Co
778
60
718
Ni
853
67
786
Cu
933
75
858
Zn
1022
89
933
Electron-nucleus attraction helps us identify the
elements
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
The Sudden Approximation
Assumes the remaining orbitals (often called the passive orbitals) are
the same in the final state as they were in the initial state (also called
the frozen
frozen--orbital approximation
approximation).
). Under this assumption, the XPS
experiment measures the negative HartreeHartree-Fock orbital energy:
Koopman’s Binding Energy
EB,K
≅ -εB,K
Actual binding energy will represent the readjustment of the NN-1
charges to minimize energy (relaxation):
EB = Ef N-1 - Ei N
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Chemical Shifts - Electronegativity Effects
Carbon--Fluorine Bond
Carbon
C 1s
Binding
Energy
Core Level
C 1s
Shift to higher
binding energy
Electron-nucleus
Electronattraction (Loss of
Electronic Screening)
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Valence Level
C 2p
Fluorine ElectroElectronegativity
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Chemical Shifts- Electronegativity Effects
C-H, C-C
Binding Energy
(eV)
285.0
amine
C-N
286.0
alcohol, ether
C-O-H, C-O-C
286.5
Cl bound to C
C-Cl
286.5
F bound to C
C-F
287.8
carbonyl
C=O
288.0
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Functional
Group
hydrocarbon
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
intensity (arb. units)
C1s of ca. ML PFN on Au(111)
290
288
286
284
282
binding energy (eV)
C1s of ca. ML PFP on Au(111)
F
F
F
F
F
F
F
F
F
F
290 288 286 284 282 280
0,6
0,4
0,2
290
288
286
284
282
binding energy (eV)
280
0,0
280
282
284
286
288
290
292
294
296
298
Binding Energy [eV]
Au(111)
Au 4f
2,0x10
intensity [arb.u]
F
C1s, TTNI
C1s, OTNI
0,8
Intensity [arb.u.]
F
F
multilayer
1.5 eV
intensity (arb. units)
F
1,0
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Electronic Effects - Spin-Orbit Coupling
3d5/2
Ag 3d
3d3/2
Orbital=s
l=0
s=+/-1/2
ls=1/2
6.0
Peak Area 2
290
288
284
280
Binding Energy (eV)
2p3/2
Cu 2p
Peak Area
1
2
955
945
935
Binding Energy (eV)
362
4f7/2
4f5/2
Peak Area
925
3
374 370 366
Binding Energy (eV)
Orbital=p
l=1
s=+/-1/2
ls=1/2,3/2
19.8
:
:
Au 4f
2p1/2
965
378
276
Orbital=d
l=2
s=+/-1/2
ls=3/2,5/2
91
3
Orbital=f
l=3
s=+/-1/2
ls=5/2,7/2
3.65
: 4
87
83
Binding Energy (eV)
79
Au(111)
Au 4f
2,0x10
intensity [arb.u]
C 1s
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Final State Effects - Shake-up/ Shake-off
Results from energy made available in the relaxation of the final state
configuration (due to a loss of the screening effect of the core level electron which
underwent photoemission)
photoemission)..
L(2p) -> Cu(3d)
Shake-up: Relaxation energy used to
excite electrons in valence levels to
bound states (monopole excitation).
Shake-off: Relaxation energy used to
excite electrons in valence levels to
unbound states (monopole ionization).
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Final State Effects- Shake-up/ Shake-off
Ni Oxide
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Ni Metal
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Final State Effects- Multiplet Splitting
Following photoelectron emission,
the remaining unpaired electron
may couple with other unpaired
electrons in the atom, resulting in
an ion with several possible final
state configurations with as many
different energies. This produces a
line which is split asymmetrically
into several components.
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Electron Scattering Effects
Energy Loss Peaks
eph + esolid
e*ph + e**solid
Photoelectrons travelling through the solid can interact with
other electrons in the material. These interactions can result in
the photoelectron exciting an electronic transition, thus losing
some of its energy (inelastic scattering).
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Electron Scattering Effects
Plasmon Loss Peak
Al 2s
a
a
a
A=15.3 eV
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Metal
a
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Electron Scattering Effects
Plasmon Loss Peak
O 1s
21 eV
x4
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Insulating
Material
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Quantitative Analysis by XPS
For a Homogeneous sample:
I = Nσ
NσDJL
DJLλ
λAT
where: N = atoms/cm3
σ = photoelectric crosscross-section, cm2
D = detector efficiency
J = XX-ray flux, photon/cm2-sec
L = orbital symmetry factor
λ = inelastic electron meanmean-free path, cm
A = analysis area, cm2
T = analyzer transmission efficiency
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Relative Sensitivities of the Elements
12
10
8
4f
6
2p
4
4d
2
1s
0
Li B N F Na Al P Cl K Sc V M Co Cu G As Br Rb Y Nb Tc Rh Ag In Sb I Cs La Pr P Eu Tb Ho T Lu Ta Re Ir Au Tl Bi
Be C O Ne M Si S Ar Ca Ti Cr Fe Ni Zn G Se Kr Sr Zr M Ru Pd Cd Sn Te Xe Ba Ce Nd S G Dy Er Yb Hf W Os Pt Hg Pb
Elemental Symbol
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Relative Sensitivity
3d
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
5
3.0x10
HATCN on Cu(111)
xx0291_1
xx0306_1
5
2.5x10
5
1.5x10
N1s
5
1.0x10
C1s
4
5.0x10
0.0
0
100
200
300
400
500
600
700
Ekin [eV]
Au(111)
Au 4f
2,0x10
intensity [arb.u]
intensity [a.u.]
5
2.0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
XPS of Copper-Nickel alloy
120
Peak
Area
Cu 2p
100
Mct-eV/sec
Ni
Cu
2.65
3.65
Atomic
Conc
%
4.044
5.321
49
51
Cu
LMM Cu
Ni
LMM Cu
LMM Ni
LMM
LMM Ni
LMM
Ni 2p
40
Ni 3p
20
Cu 3p
0
-1100
-900
-700
-500
-300
-100
Binding Energy (eV)
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Thousands
N(E)/E
80
60
Rel.
Sens.
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Escape depth – mean free path
Gezeigt ist die Abhängigkeit der freien Weglänge von Elektronen in Festkörpern in Abhängigkeit von deren
kinetischer Energie über dem Ferminiveau. Der exakte Streumechanismus ist materialabhängig, aber
insgesamt folgt der Zusammenhang einer „universellen Kurve“, die hier als Band gezeigt ist. Diese hat ein
Minimum bei ca. 50 eV. Zu beachten ist die logarithmische Auftragung an beiden Achsen [87], [88].
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
from www.lasurface.com
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
surface sensitive data
bulk sensitive data
hν=630eV
hν=190eV
surface sensitive data:
metallic signal more intense than oxidic
signal.
(b)
Au2O3
Aumet
(c)
(b)
(a)
90
85
EB [eV]
80
(a)
75
95
90
85
80
EB [eV]
Au2O3:
Au 4f 7/2 at 85.7eV binding energy,
Au (metallic) Au 4f at 84eV,
chemical shift = 1.7eV
Au(111)
Au 4f
2,0x10
intensity [arb.u]
counts [a.u.]
bulk sensitive data:
the oxidic signal exceeds the metallic Au
signal;
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
HIGH KINETIC ENERGY PHOTOELECTRON SPECTROSCOPY
(HIKE) on Thin Film Solar Cells
Zn(O,S) - 15 nm buffer layer
Cu(In,Ga)Se2 (CIGS)
Se2p
Intensity / a.u.
Cu2p
Se2p
1500eV 1480 1460 1440
Binding Energy / eV
Intensity / a.u.
Intensity / a. u.
9000eV
8000eV
7000eV
6500eV
6000eV
5500eV
5000eV
4000eV
3000eV
Glass + Mo
1420
Ga2p
Cu2p
920
940
960eV
Binding Energy / eV
Above approximately 5 keV
excitation energy the
substrate becomes visible!
2500eV
2000
1500
Binding Energy / eV
1000
Depth profiling of
the device is
possible!
Au(111)
Au 4f
Johansson, Platzer-Björkman, Gorgoi, et al, Rev. Sci. Instrum. 78 (2007) 1.
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Cs2Te photocathodes for electron accelerators: new,
contaminated, used, oxidised
composition
chemical analysis
survey @ 900eV photon energy
Cs3 3d
4
4x10
Cs and Te
signals
Te 3d
4
3x10
4
2x10
O1s
new
Mo 3d
Augers
0
200
120
3d5/2 0
80
400
600
800
1000
used
3d5/2 6+
0
565
Ekin[eV]
4
3d3/2 2-
3d5/2 2-
3d3/2 0
3d3/2 6+
plasmon peak
40
4
1x10
0
measurement 900 eV
background
160
oxidised
sample 1, new
counts / 100
Intensity [arb.units]
4
5x10
contamination
570
575
580
Eb (eV)
585
590
595
survey @ 900eV photon energy
3.5x10
Cs3 3d
sample 3, used DESY
3.0x10
Teflon
Contaminated
Cs and Te
signals
4
2.5x10
4
2.0x10
4
1.5x10
F1s
Augers
4
1.0x10
C1s
3
5.0x10
0.0
0
valence bands
Te 3d
4
200
400
Ekin[eV]
600
800
1000
exposed
to bad
vacuum
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
0
#90.1 (fresh)
#92.1 (used)
photo
emissive
band
2
4
6
core like
Cs 5p
8 10 12 14 16 18 20
Eb (eV)
Au(111)
Au 4f
2,0x10
intensity [arb.u]
4
counts
Intensity [arb.units]
4.0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Counts
Secondary electron cutoff (SECO)
HOMO or EF
Ekin,HOMO
Ekin,EF
Au(111)
Au 4f
2,0x10
intensity [arb.u]
Ekin,SECO
Ekin
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Secondary electron cutoff (SECO)
valence states
Counts
UPS: valence orbitals
interface states
HOMO or EF
Ekin,SECO
Ekin
Ekin,HOMO
Ekin,EF
C60 on CH8000
5
Z0115_1
Z0117_1
Z0119_1
Z0120_1
Z0121_1
Z0131_1
Z0132_1
Z0133_1
Z0136_1
2.4x10
5
2.2x10
5
2.0x10
5
ionization energy = hν – (Ekin,HOMO – Ekin,SECO)
work function = hν – (Ekin,EF – Ekin,SECO)
intensity [arb.u.]
1.8x10
5
1.6x10
5
1.4x10
5
1.2x10
5
1.0x10
4
8.0x10
4
6.0x10
4
4.0x10
4
2.0x10
0.0
20
25
30
35
40
Ekin [eV]
Au(111)
Au 4f
2,0x10
intensity [arb.u]
hole injection barrier = Ekin,EF – Ekin,HOMO
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Workfunction
Free
Electron
hv
Vacuum
Level, Ev
Φsample
Fermi
Level, Ef
Binding
energy
E1s
„Push-back“ effect
Charge transfer
Covalent bond formation
Permanent dipoles
Au(111)
Au 4f
intensity [arb.u]
Ishii, Sugiyama, Ito, Seki, Adv. Mater. 11, 605 (1999); Kahn, Koch, Gao, J. Poly. Sci. B 41, 2529-2548 (2003)
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
(1)
0,4
0,2
0
(2)
2
4
8
16
50
0,0
110
14
12
10
8
6
4
2
0
3
Ebinding [eV]
Eva c
energy level diagrams of
PEN/Au(111)
4
8
16
50
110
9 10 11
kinetic energy (eV)
∆va c,PEN= 0.95
φAu= 5.50
EF
2
1
0
binding energy (eV)
2
φPEN= 4.55
0.60
0.90
(1)
(2)
Au(111)
Au 4f
2,0x10
intensity [arb.u]
0,6
∆PEN
0
MT(Å)
intensity (arb. units)
Intensity [arb.units]
0,8
MT(Å)
θe= 45°
Cu(111)
Ag(111)
Au(111)
intensity (arb. units)
1,0
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
s
REMINDER
y c
k
e
Strommessung
eE
s
z
V l
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e e
e
e
Schale:
M
e
e
L
Photoemission provides
information on:
- Chemical composition
- Chemical state/reaction
- Electronic state
- Interfaces/interface reactions
- Quantitative analysis
- Depth profiling
e
e
e
K
H.-Ch. Mertins / Ch. Jung / M. Mast
Mai 2004
photoeffekt.dsf
Au(111)
Au 4f
intensity [arb.u]
2,0x10
1,5x10
6
6
1,0x10
6
5,0x10
5
Au NVV
Au 5p
Au 4d
VB
0,0
100
200
300
400
Ekin [eV]
500
600
Thank you!