PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika

Intensity, (a.u.)
200
190
180
170
160
150
J. Laurikaitienė et al. / Medical Physics in the Baltic States 7 (2009) 117 - 120
No. 5 after irradiation (D=2 Gy)
140
1100 1200 1300 1400 1500 1600 1700 1800
Intensity, (a.u.)
30
24
18
12
6
0
Raman shift, cm -1
No. 5 after irradiation (D=8 Gy)
1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
Raman shift, cm -1
Fig. 3. Raman spectra of DLC film No. 5 after 2 Gy and
8 Gy irradiation
In contrariety, the intensity ratio ID/IG has a tendency to
increase for the irradiated sample series 1G (Fig. 4). An
increase in ID/IG ratio is related to the increase in the
number and/ or size of sp 2 clusters [15]. As it was
shown in [16, 17] the increase in ID/IG ratio and G shift
towards higher wave number are associated with a
decrease both sp 3 content and optical gap energy of
a-C:H films, i.e. progressive graphitization of C takes
place after irradiation of the films. The same tendency
for G and D peaks, and ID/IG ratio variation was
described in [18] and [19] studies. It was shown hat the
shift of G and D peaks to upwards and increasing
intensity of D peak indicates a severe degradation of the
structural properties of the films, i.e. decrease of the sp 3
content.
To bring the obtained information about the influence of
X-ray irradiation on the structural changes in DLC films
up-to-date, FTIR transmittance and reflectance spectra
were investigated. Peaks around 2850 and 2920 cm −1
corresponding to the sp 3 CH2 symmetric and
asymmetric stretching modes, respectively, were found
as it is usual for a-C:H films. The strong absorption at
1640 cm −1 was attributed to the presence of sp 2 C C
bond, while peak at 1730 cm −1 was assigned to the C O
valence vibrations. Broad low intensity band observed
in the range of 3200–3400 cm −1 defined sp1 OH
stretching vibrations (Fig. 5). Only few differences in
the peak areas were found in measured IR spectra of the
irradiated samples as compared to the initial samples.
119
Intensity, (a.u.)
Intensity, (a.u.)
Intensity, (a.u.)
4
3
2
1
0
No. 1G before irradiation
1250 1300 1350 1400 1450 1500 1550 1600 1650
Raman shift, cm -1
280 No. 1G after irradiation (D=2 Gy)
275
270
265
260
255
250
245
240
235
1100 1200 1300 1400 1500 1600 1700 1800
30
25
20
15
10
5
Raman shift, cm -1
No. 1G after irradiation (D=8 Gy)
0
1100 1200 1300 1400 1500 1600 1700 1800
Raman shift, cm -1
Fig. 4 Raman spectra of DLC No. 1G before and after 2
Gy and 8 Gy irradiation fractions)
In general, most significant changes in the bonding
structure after the irradiation was observed in less dense
and highly hydrogenated (H content >30at %) samples
The structure and surface morphology of the DLC films
with well developed networking structure remained
almost the same after their irradiation making them
most promising for their application as protective
coatings in the construction of optical devices.
R, %
99,0
98,5
98,0
97,5
97,0
96,5
96,0
95,5
95,0
94,5
94,0
1636
1873
1736
2852
1500 2000 2500 3000 3500 4000
ν, cm -1
2923
3367
3845
3660
No. 1 after irradiation