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FIR study of Ag x (As 33 S 33 Se 33 ) 100-X glasses
Th Hasapis (1) , E. Hatzikraniotis (1) , K.M.Paraskevopoulos (1) , K. S. Andrikopoulos (2) , S. N. Yannopoulos (3) , T. Wagner (4)
(1) Solid State Physics, Dept. of Physics, Aristotle University of Thessaloniki
(2) Physics Division, School of Technology, Aristotle University of Thessaloniki
(3) FORTH /ICE-HT, P.O. Box 1414, GR-26504, Rio, Patras
(4) Department of General and Inorganic Chemistry, University of Pardubice, 53210 Pardubice, Czech Republic
Abstract
The structure of chalcogenide glasses Ag x (As 33 S 33 Se 33 ) 100-x with 0≤x≤22 was studied by infrared reflectance spectroscopy. The
absorption coefficient spectra, calculated from reflectance by Kramers-Kroning analysis, were deconvoluted in the frequency
range from 150-450cm -1 with six Gaussian line shape bands and the frequency and relative intensity of the component bands were
determined as a function of silver content. The 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, as a strong peak
appears at 252 cm -1 for x=18 glass composition.
Introduction
Chalcogenide glasses have attracted much attention in light of their technological applications, including infrared transmitting
optical elements, xerography, memory switching devices and materials useful for image creation and storage. The chemical
bonding determines the short-range order and consequently many physical properties. Infrared spectroscopy is a technique
sensitive to changes at the atomic level and therefore is a powerful tool for structure detection.
The major features of the vibrational spectra of As 2 S 3 and As 2 Se 3 stoichiometric glasses are determined by vibrations of
AsS 3 and AsSe 3 pyrmamidal units, respectively which are interconnected through As-S(Se)-As bridges [1,2,3]. This model can be
extended also in the case of ternary systems As x S y Se z with the resultant spectrum being a superposition of the spectra of the
constituent units [4], which are determined by the y/z ratio in the glass.Raman spectra of As 33 S 67-x Se x and Ag x (As 0.33 S 0.67-y Se y ) 100-x
amorphous films showed contributions from different structural units as pyramids AsS(Se) 3 , Se-rings, S-chains and As 3 S(Se) 6
units connected by S(Se)-Ag-S(Se) linkages with a decrease in S-S or Se-Se bonds respectively [5,6].
In this work we present infrared reflectivity spectra of Ag x (As 33 S 33 Se 33 ) 100-x glasses in order to study the effect of silver
doping on the structure of the non-stoichiometric glass matrix (As 33 S 33 Se 33 ) since the knowledge of optical properties of
amorphous bulk or thin films of Ag-As-S-Se is important for potential applications.
Experimental
Infrared spectra were recorded at nearly normal incidence in the 150-450cm -1 spectral region, at room temperature, with a Bruker
113V FTIR spectrometer. The reflection coefficient shown in figure 1 for different Ag compositions was determined by typical
sample-in-sample-out method with a gold mirror as the reference. The absorption coefficient spectra, (fig. 2) were calculated from
reflectance by Kramers-Kroning analysis, using the expression α(ω)=2π·ω·ε 2 (ω)/n(ω), where ε 2 (ω) is the imaginary part of the
dielectric function, ε=ε 1 +iε 2 , and n(ω) is the real part of the refractive index.
Reflectance
0,30
0,25
0,20
0,15
0,10
150 200 250 300 350 400 450
Wavenumber (cm -1 )
Figure 1: Infrared reflection spectra of Ag x (As 33 S 33 Se 33 ) 100-x .
For clarity the spectra are shifted vertically against each other
22
18
12
8
4
0
Absorption Coefficient (cm -1 )
4000
3500
3000
2500
2000
1500
1000
500
0
18
22
12
4 8
0
150 200 250 300 350 400 450
Wavenumber (cm -1 )
Figure 2:Absorption coefficient specrta ofAg x (As 33 S 33 Se 33 ) 100-x
Spectra have been off-set to facilitate comparison.
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