17.4 Inner Potential Constant and Work Function
341
incorporates into the Cu(001) surface. From a HREELS study Dubois [24] concluded
that oxygen chemisorbs three-fold hollow sites on the Cu(111) surface, either in or
below the outmost plane of Cu atoms, resulting in a work function change. Ertl
and Rhodin [25] suggested that the φ be due to the formation of the dipole layer.
Lauterbach and Rotermund [26] [27][28] attributed the φ to an inversion of the
oxygen dipole moment when it goes beneath the surface.
17.5 Mechanism Clarification
During the reaction, the c(2 × 2)–2O
−1 domain, or the off-centered CuO 2 pairing
pyramid evolves into the Cu 3 O 2 pairing tetrahedron that gives rise to the Cu(001)–
(2
√
2 ×
√
2)R45°–2O
−2 phase. STM images revealed creation of dipoles resulting
in, respectively, the tensile and the compressive stress [29].
Figure 17.4 illustrates the variation of the surface-charge caused by the reaction.
Compared with the clean-Cu(001) surface with ion cores arranged regularly in the
Fermi sea, as shown in panel (a), panels (b) and (c) correspond to the outmost
two atomic layers of the Cu(001)–(2
√
2 ×
√
2)R45°–2O
−2 phase. Cu 3 O 2 bonding
results in two hybridized-O
−2 ions, one Cu
+2 , two Cu
p , and a missing-row vacancy in
a complex unit cell at the top layer. In the second layer, Cu atoms in the every other row
along the [010] direction contributes one electron to the oxygen atom for tetrahedron
formation. Two Cu
+ ions are left behind in a unit cell. Panels (a) and (b) illustrate
satisfactorily the corresponding STM signatures of Jensen et al. [30]. In particular,
panel (b) can account for the depressions and the “dumb-bell” protrusions that bridge
over the missing rows.
17.5.1 Oxygen and Beam Energy Reduced V 0
The Cu 3 O 2 structure accounts well for the V 0 reduction caused by the Cu 3 O 2 bond
formation. Initially, there are four Cu atoms in a Cu(001)–(2
√
2 ×
√
2)R45°–2O
−2
unit cell at the top layer. The chemisorption of O 2 removes one Cu atom out. The
oxygen atom catches one electron from each of the top and second substrate layer.
The total number of electrons at each layer contributing to the V 0 is reduced by the
adsorption of oxygen (with 8 electrons for each O atom) and the removal of one Cu
(with each Cu atom there are 29 electrons). The transportation of the two electrons
from the second layer to the oxygen adsorbate also varies the V 0 of both the top and
the second layers. Hence, the relativistic charge quantity in the top layer is:
([29e × 2(Cu
p ) + (29 − 2)e (Cu
+2 ) + 29e × 0(MR)]
+ [(8 + 2)e × 2(O
−2 )])/[29e × 4(Cu)]
= 105/116 = 90.5%
∼ = 10.50/11.56 = 90.8% (VLEED optimization)
341
incorporates into the Cu(001) surface. From a HREELS study Dubois [24] concluded
that oxygen chemisorbs three-fold hollow sites on the Cu(111) surface, either in or
below the outmost plane of Cu atoms, resulting in a work function change. Ertl
and Rhodin [25] suggested that the φ be due to the formation of the dipole layer.
Lauterbach and Rotermund [26] [27][28] attributed the φ to an inversion of the
oxygen dipole moment when it goes beneath the surface.
17.5 Mechanism Clarification
During the reaction, the c(2 × 2)–2O
−1 domain, or the off-centered CuO 2 pairing
pyramid evolves into the Cu 3 O 2 pairing tetrahedron that gives rise to the Cu(001)–
(2
√
2 ×
√
2)R45°–2O
−2 phase. STM images revealed creation of dipoles resulting
in, respectively, the tensile and the compressive stress [29].
Figure 17.4 illustrates the variation of the surface-charge caused by the reaction.
Compared with the clean-Cu(001) surface with ion cores arranged regularly in the
Fermi sea, as shown in panel (a), panels (b) and (c) correspond to the outmost
two atomic layers of the Cu(001)–(2
√
2 ×
√
2)R45°–2O
−2 phase. Cu 3 O 2 bonding
results in two hybridized-O
−2 ions, one Cu
+2 , two Cu
p , and a missing-row vacancy in
a complex unit cell at the top layer. In the second layer, Cu atoms in the every other row
along the [010] direction contributes one electron to the oxygen atom for tetrahedron
formation. Two Cu
+ ions are left behind in a unit cell. Panels (a) and (b) illustrate
satisfactorily the corresponding STM signatures of Jensen et al. [30]. In particular,
panel (b) can account for the depressions and the “dumb-bell” protrusions that bridge
over the missing rows.
17.5.1 Oxygen and Beam Energy Reduced V 0
The Cu 3 O 2 structure accounts well for the V 0 reduction caused by the Cu 3 O 2 bond
formation. Initially, there are four Cu atoms in a Cu(001)–(2
√
2 ×
√
2)R45°–2O
−2
unit cell at the top layer. The chemisorption of O 2 removes one Cu atom out. The
oxygen atom catches one electron from each of the top and second substrate layer.
The total number of electrons at each layer contributing to the V 0 is reduced by the
adsorption of oxygen (with 8 electrons for each O atom) and the removal of one Cu
(with each Cu atom there are 29 electrons). The transportation of the two electrons
from the second layer to the oxygen adsorbate also varies the V 0 of both the top and
the second layers. Hence, the relativistic charge quantity in the top layer is:
([29e × 2(Cu
p ) + (29 − 2)e (Cu
+2 ) + 29e × 0(MR)]
+ [(8 + 2)e × 2(O
−2 )])/[29e × 4(Cu)]
= 105/116 = 90.5%
∼ = 10.50/11.56 = 90.8% (VLEED optimization)