362
19 Perspectives
surface regarding the bond geometry, bond forming dynamics and the corresponding change of atomic locations, valence DOS and the surface potential.
VLEED enables the current modeling approach to be verified and the modeling approach in turn uncovers the full capacity and reliability of the VLEED
technique.
(2) VLEED spectral sensitivity examination revealed that a 20% change of the
ReV(z) parameters cause an antiphase shift, altering the intensity of spectral
features oppositely; the spectral features are less sensitive to the ImV(z) parameters; the bond geometry parameters are more practical in responsible for the
spectral features than the individual atomic dislocations.
(3) The tetrahedron bond formation with a small number of parameters and physical constraints reflects the real process of reaction in which atoms move their
positions collectively. The model indicates that oxidation is a dynamic process of electron transportation in which O
−1 forms first and then O
−2 follows with sp-orbital hybridization and lone pair production. O
−2 prefers in the
nearly central position of a tetrahedron. Importantly, the O
−1 or nonbonding
lone pair induces metal dipoles at the surface. Besides the electron transport
between oxygen and metals, metal dipoles as well as the nonbonding states
of the hybridized O
−2 play key roles in the electronic processes and physical
properties of oxidation. For example, the strongly localized electrons with low
mobility reduce the work function and increase the contact electrical resistance.
(4) As a consequence of bond forming, the valence DOS of a metal is modified
with four additional features of O-M bonding far below E F , nonbonding lone
pairs of oxygen just below E F , antibonding metal dipoles above and the holes
below the E F . Therefore, oxygen possesses the special capacity of creating a
gap or widens the existing band gap, and adding a sub-band above E F reducing
the work function, which agrees with the PES detection of a number of metal
surfaces with chemisorbed oxygen.
(5) The single-variable parameterized SPB functions uncover the full capacity of
VLEED in simultaneously determining the bond geometry, the shape of the
SPB and the variation of the valence DOS and their interdependence. One can
judge models by simply comparing the shape of the geometrical-dependent
z 0 (E) curves.
(6) The decoding skills are proven more revealing than the traditional wisdom.
The overall approaches not only reflect properly the real process of reaction
but also reduce the numerical efforts and ensure the certainty of solution.
(7) O-Cu(001) reaction is a dynamic process that progresses in four discrete stages.
The Cu 3 O 2 configuration indicates that one Cu may donate more than one
electron to different oxygen adsorbates but one oxygen atom can never get more
than one electron from a specific Cu. This provides the basis of preferential
oxidation of a certain orientation of crystalline such as diamond (111) faces
[1].
(8) The O-Cu(001) surface bond forming is responsible for all the observations,
whether static or dynamic. Atomic dislocation and surface relaxation are determined by the bond geometry. The strong localization of surface electrons and
19 Perspectives
surface regarding the bond geometry, bond forming dynamics and the corresponding change of atomic locations, valence DOS and the surface potential.
VLEED enables the current modeling approach to be verified and the modeling approach in turn uncovers the full capacity and reliability of the VLEED
technique.
(2) VLEED spectral sensitivity examination revealed that a 20% change of the
ReV(z) parameters cause an antiphase shift, altering the intensity of spectral
features oppositely; the spectral features are less sensitive to the ImV(z) parameters; the bond geometry parameters are more practical in responsible for the
spectral features than the individual atomic dislocations.
(3) The tetrahedron bond formation with a small number of parameters and physical constraints reflects the real process of reaction in which atoms move their
positions collectively. The model indicates that oxidation is a dynamic process of electron transportation in which O
−1 forms first and then O
−2 follows with sp-orbital hybridization and lone pair production. O
−2 prefers in the
nearly central position of a tetrahedron. Importantly, the O
−1 or nonbonding
lone pair induces metal dipoles at the surface. Besides the electron transport
between oxygen and metals, metal dipoles as well as the nonbonding states
of the hybridized O
−2 play key roles in the electronic processes and physical
properties of oxidation. For example, the strongly localized electrons with low
mobility reduce the work function and increase the contact electrical resistance.
(4) As a consequence of bond forming, the valence DOS of a metal is modified
with four additional features of O-M bonding far below E F , nonbonding lone
pairs of oxygen just below E F , antibonding metal dipoles above and the holes
below the E F . Therefore, oxygen possesses the special capacity of creating a
gap or widens the existing band gap, and adding a sub-band above E F reducing
the work function, which agrees with the PES detection of a number of metal
surfaces with chemisorbed oxygen.
(5) The single-variable parameterized SPB functions uncover the full capacity of
VLEED in simultaneously determining the bond geometry, the shape of the
SPB and the variation of the valence DOS and their interdependence. One can
judge models by simply comparing the shape of the geometrical-dependent
z 0 (E) curves.
(6) The decoding skills are proven more revealing than the traditional wisdom.
The overall approaches not only reflect properly the real process of reaction
but also reduce the numerical efforts and ensure the certainty of solution.
(7) O-Cu(001) reaction is a dynamic process that progresses in four discrete stages.
The Cu 3 O 2 configuration indicates that one Cu may donate more than one
electron to different oxygen adsorbates but one oxygen atom can never get more
than one electron from a specific Cu. This provides the basis of preferential
oxidation of a certain orientation of crystalline such as diamond (111) faces
[1].
(8) The O-Cu(001) surface bond forming is responsible for all the observations,
whether static or dynamic. Atomic dislocation and surface relaxation are determined by the bond geometry. The strong localization of surface electrons and