Analysis of as received samples
Chemical composition of the samples:
We remind that the surface region observed was on the flat part of the couples. Both
surfaces CLIC I and CLIC IIa (figure 1)are strongly contaminated by C and some traces
of Si, as summarized in table I and comared to the reference (surface of the cut).
Sample/
element
CLIC I
CLIC IIa
reference
Table I
C[%]
O[%]
Cu[%]
Si[%]
66.2
65.7
79.1
23.1
23.1
14.2
1.3
3.5
2.4
9.4
7.8
4.4
The fact that Si is present also on the cut reference face might indicate that part of the Si
contamination is generated by the packaging in the plastic bag after cutting. However,
this hypothesis can be discarded, since we measured the surface composition of a copper
sample, which was stored for 2 hours in a similar plastic bag and we did not find any
trace of Si. The Si intensity (peak area) for the CLICI and CLICIIa samples is almost
twice as large as on the reference. No clear conclusions can be drawn about the origin of
the Si.
III
I
IIa
XP
SS
Figure 1
Chemical species:
Both samples have identical Cu2p spectra (worse signal to noise on CLIC I). The Cu 2p
peaks (fig 2) indicate the presence of at least two types of Cu within the probing depth of
the XPS technique. The main contribution is at 932.4eV and the lower one is around
934.6 eV. From the position of the LMM Auger line at 336.7 eV we can conclude that Cu
is mainly present as Cu2O. The minor contribution can be ascribed to Cu(OH)2 : no
traces of metallic Cu or CuO are detected. This minor contribution almost vanishes after
about 30 minutes irradiation, which is the time needed to acquire the multiplex spectrum,
therefore its true intensity is higher than the measured one.
The reference sample exhibits only the main peak at 932.8 eV (a shift 0f about 0.4eV
with respect to the other samples might be given by adjustment problem due to shape of
the sample and is systematic on all lines) and no minor peak. The Cu LMM line has
maximum at 336.8eV with a shoulder at 339.6eV, which could not be ascribed to any
known Cu feature. We conclude that Cu is present as Cu2O in this case too.
The O1s line (fig 3) is similar for all samples and is constituted of at least two
components: the main peak is at 532-532.3 eV and the other (about 1/5-1/6 of the total
intensity) at 530.5-530.7 eV. The second peak corresponds to the oxygen in Cu2O oxide,
whereas the main component is more difficult to interpret. It might be due to water,
hydroxides or oxygen containing hydrocarbons. It is not correlated to the Cu 2p peak
ascribed to Cu(OH)2 since it does not markedly decrease upon irradiation..
The energy position of the Si 2p line corresponds to silicones and/or silicates (102102.4eV) on all samples. However , the fact that no other impurity elements are detected
seems to discard the possibility to have silicates.
Cu 2p lines on CLIC IIa
Cu2O
intensity [a.u.]
Cu(OH)2 ?
35000
980
970
960
950
binding energy [eV]
figure 2
940
930
920
O1s line of CLIC IIa
35000
contaminants
33000
Intensity [a.u.]
31000
29000
Cu2O
27000
25000
23000
21000
19000
17000
540
538
536
534
532
530
528
526
binding energy [eV]
Figure 2
XPS data for CLIC surfaces
90
concentrations [at%]
80
70
60
C[%]
O[%]
Si[%]
Cu[%]
50
40
30
20
10
0
CLIC I
CLIC IIa
Ref
524