6.5 Copper
117
(1) The m value increases from unity for Cu/HOPG/Ar
+ to 1.30 for Cu/CYCL and to
1.82 for Cu/CYCL/Ar
+ , which indicates that the Cu is more reactive with CYCL
than with HOPG. Cu atoms react hardly with carbon at room temperature [74]
but it reacts easily with polymers [75, 76]. Although the Ar
+ does not react
with Cu, Ar
+ bombardment promotes the Cu/CYCL reaction by heating and
impacting.
(2) The m value increases from 1.3 for Cu/CYCL to 1.96 for Cu/CYCL/N
+ . N
+ -
bombardment alters the surface bond from metallic to ionic that enhances the
crystal potential [77].
(3) The layer-by-layer growth fashion (τ = 1) of Cu films on Al 2 O 3 could fit the
results better though dispute remains on the growth mode of metal on oxide
surfaces ([78] and references therein). The m increase from 1.27 at 80 K to 1.94
at 300 K for Cu/Al 2 O 3 indicates that Cu bonds to oxygen atom more easily at
room temperature than at lower temperatures [65].
(4) The η ML ∼ = 1.25 means that the strength of crystal binding to the M(3d) level is
25% stronger than that to the deeper L(2p) level.
(5) The κ ML in Fig. 6.12d–f is independent of the shape and size of the particle but
it is sensitive to the chemical treatment. If charge transfers from one constituent
to another, the κ ML will change, otherwise it is unity, as compared in Table 6.3
for the conditioned Cu crystals.
6.6 Nickel
6.6.1 NEXAFS-XPS: Shell-Resolved Entrapment
Figure 6.13 shows the near edge X-ray absorption fine structure (NEXAFS) spectra,
which revealed the sublayer-resolved Ni 2p shift [79]. The 2p shifts positively and the
outermost layer shifts most. Low-energy electron diffraction (LEED) measurement
also revealed that the first Ni(110) layer spacing contracts by 9.8 ± 1.8% with respect
to the bulk lattice constant [80]. These observations evidence the BOLS prediction
on the skin bond contraction and the associated local quantum entrapment.
6.6.2 APECS: 2p and 3d Band Cooperative Shift
Figure 6.14 displays the XPS 2p 3/2 spectra and (b) the TEM images of Ni crystals
deposited on SiO 2 substrates. Results indicate that the 2p peak undergoes quantum
entrapment due to particle size reduction [81]. The thickness dependent APECS
spectra in Fig. 6.15 demonstrate that the (a) E 2p1/2 , (b) E 2p3/2 , (c) E k (LMM), and
(d) E 3d5/2 shift positively but the E K negatively when the Ni/TiO 2 film becomes
thinner [82]. The broad 3d 5/2 band contains the 4s band contribution. NEXAFS,
117
(1) The m value increases from unity for Cu/HOPG/Ar
+ to 1.30 for Cu/CYCL and to
1.82 for Cu/CYCL/Ar
+ , which indicates that the Cu is more reactive with CYCL
than with HOPG. Cu atoms react hardly with carbon at room temperature [74]
but it reacts easily with polymers [75, 76]. Although the Ar
+ does not react
with Cu, Ar
+ bombardment promotes the Cu/CYCL reaction by heating and
impacting.
(2) The m value increases from 1.3 for Cu/CYCL to 1.96 for Cu/CYCL/N
+ . N
+ -
bombardment alters the surface bond from metallic to ionic that enhances the
crystal potential [77].
(3) The layer-by-layer growth fashion (τ = 1) of Cu films on Al 2 O 3 could fit the
results better though dispute remains on the growth mode of metal on oxide
surfaces ([78] and references therein). The m increase from 1.27 at 80 K to 1.94
at 300 K for Cu/Al 2 O 3 indicates that Cu bonds to oxygen atom more easily at
room temperature than at lower temperatures [65].
(4) The η ML ∼ = 1.25 means that the strength of crystal binding to the M(3d) level is
25% stronger than that to the deeper L(2p) level.
(5) The κ ML in Fig. 6.12d–f is independent of the shape and size of the particle but
it is sensitive to the chemical treatment. If charge transfers from one constituent
to another, the κ ML will change, otherwise it is unity, as compared in Table 6.3
for the conditioned Cu crystals.
6.6 Nickel
6.6.1 NEXAFS-XPS: Shell-Resolved Entrapment
Figure 6.13 shows the near edge X-ray absorption fine structure (NEXAFS) spectra,
which revealed the sublayer-resolved Ni 2p shift [79]. The 2p shifts positively and the
outermost layer shifts most. Low-energy electron diffraction (LEED) measurement
also revealed that the first Ni(110) layer spacing contracts by 9.8 ± 1.8% with respect
to the bulk lattice constant [80]. These observations evidence the BOLS prediction
on the skin bond contraction and the associated local quantum entrapment.
6.6.2 APECS: 2p and 3d Band Cooperative Shift
Figure 6.14 displays the XPS 2p 3/2 spectra and (b) the TEM images of Ni crystals
deposited on SiO 2 substrates. Results indicate that the 2p peak undergoes quantum
entrapment due to particle size reduction [81]. The thickness dependent APECS
spectra in Fig. 6.15 demonstrate that the (a) E 2p1/2 , (b) E 2p3/2 , (c) E k (LMM), and
(d) E 3d5/2 shift positively but the E K negatively when the Ni/TiO 2 film becomes
thinner [82]. The broad 3d 5/2 band contains the 4s band contribution. NEXAFS,