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x=18
x=18
Infrared Absorption
x=12
Infrared Absorption
x=12
x=0
x=0
200 210 220 230 240 250 260 270 280
Wavenumber (cm -1 )
280 300 320 340 360 380 400
Wavenumber (cm -1 )
Figure 3: Examples of deconvolution of the low frequency (left) and high frequency (right) envelope of Ag x (As 33 S 33 Se 33 ) 100-x
glasses. Dashed lines represent the three Gaussian component bands.
Results
Figure 1 presents infrared reflectance spectra of Ag x (As 33 S 33 Se 33 ) 100-x glasses and figure 2 the respective absorption coefficient
spectra. The measured reflectivity spectra show two distinct broad peaks in the spectral regions 200-280 cm -1 and 290-400 cm -1
which can be attributed to different structural pyramidal units AsSe 3 and AsS 3 , respectively. As Ag content increases these
dominant bands become broader and shift to lower frequencies. Inspection of figure 2 shows that Ag influences these two bands
in a way that the maximum position of the strongest peak moves upwards for AsSe 3 and downwards for AsS 3 pyramidal units,
while in both cases there is a shoulder that exhibits an intensity increase. Especially for the lower frequency envelope the
spectrum corresponding to x=18 glass shows an inversed behavior of these two peaks.
Figure 3 shows the infrared absorption coefficient, for selected glasses, in an expanded frequency scale for the two
absorption envelopes. The profile of the envelopes suggests the existence of three component bands and a good fit was obtained
with three bands of Gaussian line shape. For the lower frequency envelope the first band moves to lower frequency showing a
broadening and an increase in intensity. The second band moves to higher frequency and exhibits a considerable decrease of its
intensity and a broadening as x increases. The third deconvoluted band moves also downwards and its peak position is fixed at
252 cm -1 for the x=22 sample while its contribution to the absorption coefficient spectrum becomes dominant. As far as the higher
frequency envelope is concerned, the first Gaussian band shifts to lower frequencies with decreased intensity. The peak positions
of the other two deconvoluted bands are unaffected by Ag content, while the contribution of the last one increases with increasing
x. Results were found to be consistent with a glass structure formed by AsSe 3 and AsS 3 pyramidal units with the silver content to
influence mostly the arsenic-selenium component of the glasses.
Acknowledgment.
We acknowledge financial support from GSRT (Ministry of Development) in the framework of the program PENED 2003
(03ΕΔ887). The Hellenic Telecommunications Organization (OTE S.A.) is also thanked for support.
References.
[1] Lucovsky G., Phys. Rev. B 6 (1972) 1480.
[2] Lucovsky G., Martin R., J. Non-Cryst. Solids 8-10 (1972) 185.
[3] Giehler M.,phys. stat. sol. (b) 106 (1981) 193.
[4] Lucovsky G., Mat. Res. Bull. 4 (1969) 505.
[5] Kohoutek T., Wagner T.,Vlcek Mil., Vlcek Mir, Frumar M., J. Non-Cryst. Solids 352 (2006) 1563.
[6] Krbal M., Wagner T., Vlcek Mil, Vlcek Mir, Frumar M., J. Non-Cryst. Solids 352 (2006) 2662.
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