On the relation between gas phase electron scattering and processes at the STM tip - PowerPoint PPT Presentation

Loading...

PPT – On the relation between gas phase electron scattering and processes at the STM tip PowerPoint presentation | free to download - id: 6abbd2-NDVjZ



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

On the relation between gas phase electron scattering and processes at the STM tip

Description:

On the relation between gas phase electron scattering and processes at the STM tip (with emphasis on vibrational excitation) Michael Allan Department of Chemistry – PowerPoint PPT presentation

Number of Views:11
Avg rating:3.0/5.0
Slides: 36
Provided by: Michael2348
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: On the relation between gas phase electron scattering and processes at the STM tip


1
On the relation between gas phase electron
scattering and processes at the STM tip (with
emphasis on vibrational excitation)
Michael Allan Department of Chemistry University
of Fribourg, Switzerland
2
typical references
Electron collisions
STM
H. Gawronski, M. Mehlhorn, K. Morgenstern, Science
319, 930 (2008) M. Paulsson, T. Frederiksen, H.
Ueba, N. Lorente, and M. Brandbyge, Phys. Rev.
Lett. 100, 226604 (2008) Peter Liljeroth, Jascha
Repp, Gerhard Meyer, Science 317, 31, 1203
(2007) B. C. Stipe, M. A. Rezaei, W. Ho, Science
280, 1732 (1998) P. A. Sloan and R. E.
Palmer, Nature 434, 367 (2005)
G. A. Gallup and I. I. Fabrikant, Phys. Rev. A
75, 032719 (2007) O. Sueoka and S. Mori, J.
Phys. B 19, 4035 (1986) G. J. Schulz, Rev. Mod.
Phys. 45, 423 (1973) Isobel C. Walker, A.
Stamatovic and S. F. Wong, J. Phys. Chem. 69,
5532 (1978) E. Brüche Ann. Phys. Lpz. 2, 909
(1929)
3
Terms and methods
Spatial resolution
n. a.
Cross section
Differential tunneling conductance, action
spectroscopy
phonon excitation, phonon emission, inelastic
electron-phonon effect
Vibrational excitation
EELS Electron energy-loss spectrum
IETS Inelastic Electron Tunneling Spectroscopy
Local Density of States
Resonances
4
electron scattering vs. electron tunneling
see B. N. J. Persson and A. Baratoff,
Phys. Rev. Lett. 59, 339 (1987) J. J. Pascual,
Eur. Phys. J. D 35, 327 (2005)
see G. J. Schulz, Rev. Mod. Phys. 45, 423 (1973)
5
1st glimpse
SCIENCE 1998
6
incident electron energy distribution
7
Differential tunneling conductance
Cross section
8
observing resonances
JASCHA REPP GERHARD MEYER Phys. Unserer Zeit
2006
9
observing vibrations
10
observing vibrations
M. A. Gata and P. R. Antoniewicz, PRA 1993
G. A. Gallup and I. I. Fabrikant, PRA 1993
11
observing vibrations theoretical formalism
(eA0 D0) 0.45 eV G0 -0.4 eV Re(cA0)
-0.2 eV Im(cA0) 0.1 eV
M. A. Gata and P. R. Antoniewicz, PRA 1993
(other formalisms N. Lorente etc.)
12
observing vibrations electron-phonon coupling
above threshold
  • at threshold only
  • elastic and inelastic together
  • Energy-analysis of scattered electrons permits
  • separation of elastic and inelastic channels
  • measurement of inelastic cross section
    (electron-phonon coupling) as a function of
    excess energy (EDS)

?
M Allan and I I Fabrikant, J Phys B 2002
13
observing vibrations
Electron energy-loss (eV)
Allan, Phys. Rev. Lett. (2001)
p shape resonance
virtual state
Dipole-bound states Vibrational Feshbach
Resonances (VFR)
Cížek, Horácek, Allan, Fabrikant, Domcke, J.
Phys. B (2003)
14
observing vibrations
15
observing vibrations
Energy-analysis of scattered electrons allows
vibrations to be observed
No analyzer
  1. elastic and inelastic processes measured together
    (except action spectroscopy !)
  2. vibrational spectra are measured at threshold
  1. separately from elastic process
  2. at or above threshold Ei can be chosen to hit
    various resonances

Cross section can be recorded as a function of DE
(ELS) ? spectrum of vibrational states Ei
(EDS) ? spectrum of resonances
Resonant enhancement only when there is a
resonance at vibrational threshold
16
shift of resonances due to substrate and tip
N2O on Cu
K. J. Franke, I. Fernández-Torrente, J. I.
Pascual and N. Lorente, PCCP 10, 1640 (2008)
17
peculiarities near threshold in N2O VFR
Dissociative attachment in N2O
K. J. Franke, I. Fernández-Torrente, J. I.
Pascual and N. Lorente, PCCP 10, 1640 (2008)
Vibrational Feshbach Resonances in Excitation of
high vibrational levels
18
shift of resonances due to substrate and tip
N2 on Ar on Pt
gas phase
D. C. Marinica, D. Teillet-Billy, J. P. Gauyacq,
M. Michaud and L. Sanche, Phys. Rev. B, 64,
085408 (2001)
19
role of angular momentum
Angular distribution of scattered electrons
20
role of angular momentum
Benzene on Cu
external vibrations - frustrated translation -
frustrated rotations
J. I. Pascual, J. J. Jackiw, Z. Song, P. S.
Weiss, H. Conrad, and H.-P. Rust, Phys. Rev.
Lett. 86, 1050 (2001)
21
VE by electron collisions
  • dipole excitation
  • forward scattering
  • low energies
  • resonant excitation
  • selectivity related to temporarily occupied
    orbital
  • partial waves
  • exotic mechanisms
  • dipole bound resonances Vibrational Feshbach
    Resonances (VFR)
  • virtual states (remember CO2)

22
Selectivity related to temporarily occupied
orbital
Force field
b2g ? b2g a1g
totally symmetric vibrations only
23
Selectivity special case 1
Force field pu ? pu sg
n8 pu
n6 pg
2n8 sg
2n6 sg
OK
24
Selectivity special case 2
S. F. Wong and G. J. Schulz, Phys. Rev. Lett. 35,
1429 (1975)
p
s
Vibrational excitation in benzene by electron
impact via resonances Selection rules
p
s
Observation in-plane modes, but also
out-of-plane modes
p
p
Proposition incoming dp outgoing dp wave pu
? pu sg incoming dp outgoing ss wave pu ? sg
pu
M. Paulsson, T. Frederiksen, H. Ueba, N. Lorente,
and M. Brandbyge, Phys. Rev. Lett. 100, 226604
(2008)
25
Selectivity special case 2
M. Paulsson, T. Frederiksen, H. Ueba, N. Lorente,
and M. Brandbyge, Phys. Rev. Lett. 100, 226604
(2008)
S. F. Wong and G. J. Schulz, Phys. Rev. Lett. 35,
1429 (1975)
26
Chlorobenzene
C-Cl stretch
ring breathing
- the p resonances act as doorway states into
the s resonance - no activation barrier ?
symmetry lowering ? vibronic coupling
Skalický, Chollet, Pasquier, Allan, Phys. Chem.
Chem. Phys. 2002
27
Chlorobenzene
Skalický, Chollet, Pasquier, Allan, Phys. Chem.
Chem. Phys. 2002
28
Chlorobenzene
Chlorobenzene on Si(111)
Two-electron dissociation of single molecules by
atomic manipulation at room temperature
P. A. Sloan and R. E. Palmer, Nature 434, 367
(2005)
Skalický, Chollet, Pasquier, Allan, PCCP 2002
29
the great strength of STM spatial resolution
surface phonons excited with atomic resolution
spatial mapping the 2nd derivative of I
d2I/dV2
phonon excitation probability varies with the
lateral position of the tip
?
H. Gawronski, M. Mehlhorn, K. Morgenstern,
Science 319, 930 (2008)
30
the great strength of STM spatial resolution
acetylene chemisorbed on Cu(100) C-D stretch
excited with atomic resolution
image of the 266 mV inelastic signal
normal constant current image
B. C. Stipe, M. A. Rezaei, W. Ho, Phys. Rev.
Lett. 82, 1724 (1999)
31
the great strength of STM action spectroscopy
cis-2-butene on Pd(110) vibration induced motion
Yasuyuki Sainoo, Yousoo Kim, Toshiro Okawa,
Tadahiro Komeda, Hidemi Shigekawa, and Maki
Kawai1, Phys. Rev. Lett. 95, 246102 (2005)
32
The great strength of STM product identification
after chemical change
4-dimethyl-amino-azobenzene-4-sulfonic acid
(C2H6N-C6H4NNC6H4SO3-Na) in trans- and
cis-configuration
IET manipulation of a single 4-dimethyl-amino-azob
enzene-4-sulfonic acid molecule (a) molecule in
trans-configuration before manipulation the STM
tip is positioned above the NN group of the
molecule (position marked by cross), while
the manipulation voltage is increased within 1 s
from 100 mV to 1 V (b) after manipulation the
molecule is found in cis-configuration (Itunnel
75 pA Vsample 180 mV)
Karina Morgenstern, Acc. Chem. Res., 2009, 42, 213
33
Current-Induced Hydrogen Tautomerization of
Naphthalocyanine
P. Liljeroth, J. Repp, G. Meyer, Science 317,
1203 (2007)
34
Electron collisions with pyrrole
Vibrational excitation
Dissociative attachment
T. Skalický and M. Allan, J. Phys. B (2004)
35
(No Transcript)
About PowerShow.com