18.2 Geometrical Examination
351
[5, 6]. Further evidence for the post-saturation effect is that the relaxation of the
layer spacing increases with oxygen exposure.
(2) The results of the geometrical sensitivity examination, especially panels (e) and
(f), incredibly coincide with the trends in the measurements of panels (b) and
(c), respectively. This observation indicates that the process of the Cu 2 O bond
forming dominates the spectral features while the SPB change is insignificantly
sensitive to the oxygen exposures. It is therefore further evidenced that the bond
variables are realistic and that the corresponding parameterization of the SPB
is reasonably correct.
(3) The four discrete reaction stages can be simply expressed in terms of a corresponding variation of the bond variables. For instances, features appeared in the
range from 35 to 200 L are dominated by the increase of ∠1O2, while features
for the exposure greater than 200 L are dominated by the DCu x alone. From 30
to 35 L, the recovery of the peak at 7.1 eV can be realized by increasing the Q 2
with smaller ∠1O2 and smaller DCu x .
(4) Calculation by varying the DCu z was also carried out to examine the effect of
individual atomic shift. Variation of DCu z gives a little change of the spectral
intensity between 9.5 and 11.5 eV, indicating again that the individual atomic
shift describes an untrue reaction kinetics.
It is feasible to find optimal bond parameters from the 400 L result for different
oxygen exposures. By assuming that the z 0 (E) is insensitive to the exposures, we
repeated calculations to match the intensities of the three peaks of all the measurements in Fig. 18.1a–c. The calculations were performed with a careful search over
large range and smaller steps of the variables. Table 18.1 lists the optimal structural
parameters for structures at various exposures.
18.3 Four-Stage Cu 3 O 2 Bonding and Band Forming
Kinetics
VLEED calculations at other exposures with the optimal geometry values in
Table 18.1 confirmed that the SPB is relatively insensitive to the oxygen-exposure.
Figure 18.2 shows the offset z 0 (E) profiles that produce the ImV(E, φ L ) curves and
duplicate the measured spectra in Fig. 18.1a–c. It is seen that the z 0 (E) curves, in
general, are insignificantly sensitive to the oxygen exposure. They are similar in
shape except for minimal variations above 7.5 eV at 25 L exposure. This further
evidences for the assumption that the VLEED reflectance is less sensitive to the SPB
than to the bond geometry during exposure increasing. The slight outward-shift (-z
direction, relative to −2.5 a.u. as indicated by broken lines) of the z 0 (E) curves at
higher exposures increases the n(E); and as a result, the increase of the n(E) reduces
the work function and attenuates the amplitude of the reflected beams.
The z 0 (E) is the contribution of occupied DOS, n(E), that is convoluted by real
space (local spatial DOS n(x, y)) due to multiple-diffraction but the convolution is
351
[5, 6]. Further evidence for the post-saturation effect is that the relaxation of the
layer spacing increases with oxygen exposure.
(2) The results of the geometrical sensitivity examination, especially panels (e) and
(f), incredibly coincide with the trends in the measurements of panels (b) and
(c), respectively. This observation indicates that the process of the Cu 2 O bond
forming dominates the spectral features while the SPB change is insignificantly
sensitive to the oxygen exposures. It is therefore further evidenced that the bond
variables are realistic and that the corresponding parameterization of the SPB
is reasonably correct.
(3) The four discrete reaction stages can be simply expressed in terms of a corresponding variation of the bond variables. For instances, features appeared in the
range from 35 to 200 L are dominated by the increase of ∠1O2, while features
for the exposure greater than 200 L are dominated by the DCu x alone. From 30
to 35 L, the recovery of the peak at 7.1 eV can be realized by increasing the Q 2
with smaller ∠1O2 and smaller DCu x .
(4) Calculation by varying the DCu z was also carried out to examine the effect of
individual atomic shift. Variation of DCu z gives a little change of the spectral
intensity between 9.5 and 11.5 eV, indicating again that the individual atomic
shift describes an untrue reaction kinetics.
It is feasible to find optimal bond parameters from the 400 L result for different
oxygen exposures. By assuming that the z 0 (E) is insensitive to the exposures, we
repeated calculations to match the intensities of the three peaks of all the measurements in Fig. 18.1a–c. The calculations were performed with a careful search over
large range and smaller steps of the variables. Table 18.1 lists the optimal structural
parameters for structures at various exposures.
18.3 Four-Stage Cu 3 O 2 Bonding and Band Forming
Kinetics
VLEED calculations at other exposures with the optimal geometry values in
Table 18.1 confirmed that the SPB is relatively insensitive to the oxygen-exposure.
Figure 18.2 shows the offset z 0 (E) profiles that produce the ImV(E, φ L ) curves and
duplicate the measured spectra in Fig. 18.1a–c. It is seen that the z 0 (E) curves, in
general, are insignificantly sensitive to the oxygen exposure. They are similar in
shape except for minimal variations above 7.5 eV at 25 L exposure. This further
evidences for the assumption that the VLEED reflectance is less sensitive to the SPB
than to the bond geometry during exposure increasing. The slight outward-shift (-z
direction, relative to −2.5 a.u. as indicated by broken lines) of the z 0 (E) curves at
higher exposures increases the n(E); and as a result, the increase of the n(E) reduces
the work function and attenuates the amplitude of the reflected beams.
The z 0 (E) is the contribution of occupied DOS, n(E), that is convoluted by real
space (local spatial DOS n(x, y)) due to multiple-diffraction but the convolution is