17.5 Mechanism Clarification
343
The Cu 3 O 2 structure explains that the φ originates from the formation of the
antibonding dipoles. Induction of electrons by either the O
−1 or the nonbonding lone
pairs of the O
−2 fill up the antibonding sub-band. In real space, the dipoles buckle up
with expansion of sizes and elevation of energy states. The buckling dipole changes
nothing about the net charge of the surface layer but shifts the critical position z 0
outward of the surface, which increases the saturation degree of the SPB. Therefore,
the dipoles have no apparent influence on the V 0 but occupy the empty DOS above
E F . Because VLEED integrates over large area of surface, it is impractical to try to
discriminate the V 0 from site to site on the surface but one can recognize the local
work function due to dipole formation.
17.6 Summary
The muffin-tin inner potential constant V 0 is related to the quantity of net charges
while the local work function φ(x, y, E) depends on the z-dimensional distribution and
energy dependence of the polarized electrons. The Cu 3 O 2 bonding scheme explains
the oxygen-reduced V 0 as arisen from charge transportation during reaction. The
V 0 drops by 9.5% and 3.5% for the outermost two atomic layers but the VLEED is
only sensitive to the first with 9.8% reduction. The buckling dipoles and the extent
of polarization reduce the φ(x, y, E) by increasing the occupied DOS at surface
while the dipoles affect little the V 0 . It is also justified that at very-low energies the
exchange-interaction between the incident beams and the surface ions is too weak
to affect either the quantity or the distribution of the surface charges. Therefore,
VLEED is an ideal means to collect non-destructive information about the behavior
of surface electrons in terms of inner potential constant and work function.
Decoding the angle-resolved VLEED spectra has enabled determination of the
first two Brillouin zones, the effective electron mass, lattice reconstruction, Cu 3 O 2
bond geometry, energy bands and the energy states due to the nonbonding lone
pairs of O
−2 . Consistency between calculations and measurements further verifies
the adequacy of the VLEED spectrometrics for exploring information of the bond
geometry, SPB and the valence states for chemisorbed surfaces.
References
1. K.W. Jacobsen, Theory of the oxygen-induced restructuring of Cu (110) and Cu (100) surfaces.
Phys. Rev. Lett. 65(14), 1788 (1990)
2. G. Hitchen, S. Thurgate, Determination of azimuth angle, incidence angle, and contactpotential difference for low-energy electron-diffraction fine-structure measurements. Phys.
Rev. B 38(13), 8668 (1988)
3. G. Hitchen, S. Thurgate, Azimuthal angular dependence of LEED fine structure from Cu (001).
Surf. Sci. 197(1–2), 24–34 (1988)
343
The Cu 3 O 2 structure explains that the φ originates from the formation of the
antibonding dipoles. Induction of electrons by either the O
−1 or the nonbonding lone
pairs of the O
−2 fill up the antibonding sub-band. In real space, the dipoles buckle up
with expansion of sizes and elevation of energy states. The buckling dipole changes
nothing about the net charge of the surface layer but shifts the critical position z 0
outward of the surface, which increases the saturation degree of the SPB. Therefore,
the dipoles have no apparent influence on the V 0 but occupy the empty DOS above
E F . Because VLEED integrates over large area of surface, it is impractical to try to
discriminate the V 0 from site to site on the surface but one can recognize the local
work function due to dipole formation.
17.6 Summary
The muffin-tin inner potential constant V 0 is related to the quantity of net charges
while the local work function φ(x, y, E) depends on the z-dimensional distribution and
energy dependence of the polarized electrons. The Cu 3 O 2 bonding scheme explains
the oxygen-reduced V 0 as arisen from charge transportation during reaction. The
V 0 drops by 9.5% and 3.5% for the outermost two atomic layers but the VLEED is
only sensitive to the first with 9.8% reduction. The buckling dipoles and the extent
of polarization reduce the φ(x, y, E) by increasing the occupied DOS at surface
while the dipoles affect little the V 0 . It is also justified that at very-low energies the
exchange-interaction between the incident beams and the surface ions is too weak
to affect either the quantity or the distribution of the surface charges. Therefore,
VLEED is an ideal means to collect non-destructive information about the behavior
of surface electrons in terms of inner potential constant and work function.
Decoding the angle-resolved VLEED spectra has enabled determination of the
first two Brillouin zones, the effective electron mass, lattice reconstruction, Cu 3 O 2
bond geometry, energy bands and the energy states due to the nonbonding lone
pairs of O
−2 . Consistency between calculations and measurements further verifies
the adequacy of the VLEED spectrometrics for exploring information of the bond
geometry, SPB and the valence states for chemisorbed surfaces.
References
1. K.W. Jacobsen, Theory of the oxygen-induced restructuring of Cu (110) and Cu (100) surfaces.
Phys. Rev. Lett. 65(14), 1788 (1990)
2. G. Hitchen, S. Thurgate, Determination of azimuth angle, incidence angle, and contactpotential difference for low-energy electron-diffraction fine-structure measurements. Phys.
Rev. B 38(13), 8668 (1988)
3. G. Hitchen, S. Thurgate, Azimuthal angular dependence of LEED fine structure from Cu (001).
Surf. Sci. 197(1–2), 24–34 (1988)