Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering

Resonant Raman spectra of stoichiometric glass (g) g-As₄₀Se₆₀ have been investigated. It was observed that the increasing of excitation radiation energy hv>E₀ (E₀ is pseudogap width) changes a shape, intensity, and position of Raman peaks of g-As₄₀Se₆₀. The structure and vibration spectra of some...

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Дата:2004
Автори: Mateleshko, N., Mitsa, V., Veres, M., Koos, M., Stronski, A.
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Мова:English
Опубліковано: Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України 2004
Назва видання:Semiconductor Physics Quantum Electronics & Optoelectronics
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Цитувати:Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering / N. Mateleshko, V. Mitsa, M. Veres, M. Koos, A. Stronski // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2004. — Т. 7, № 2. — С. 171-174. — Бібліогр.: 19 назв. — англ.

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spelling nasplib_isofts_kiev_ua-123456789-1181692025-02-23T17:54:36Z Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering Mateleshko, N. Mitsa, V. Veres, M. Koos, M. Stronski, A. Resonant Raman spectra of stoichiometric glass (g) g-As₄₀Se₆₀ have been investigated. It was observed that the increasing of excitation radiation energy hv>E₀ (E₀ is pseudogap width) changes a shape, intensity, and position of Raman peaks of g-As₄₀Se₆₀. The structure and vibration spectra of some As-Se clusters were calculated applying the ab initio method. In order to elucidate structural features of g-As₄₀Se₆₀, we combined the experimental Raman data and theoretical calculations. Authors wish to acknowledge Prof. F. Billes and P-G. S. R. Holomb for calculations and discussions. This work was supported by the Grant No. М/467- 2003 and Grant No. 29/48-2001 (Мinistry of education and science of Ukraine and Hungarian Science and Technology Foundation). 2004 Article Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering / N. Mateleshko, V. Mitsa, M. Veres, M. Koos, A. Stronski // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2004. — Т. 7, № 2. — С. 171-174. — Бібліогр.: 19 назв. — англ. 1560-8034 PACS: 61.43.-j, 78.30.-j https://nasplib.isofts.kiev.ua/handle/123456789/118169 en Semiconductor Physics Quantum Electronics & Optoelectronics application/pdf Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description Resonant Raman spectra of stoichiometric glass (g) g-As₄₀Se₆₀ have been investigated. It was observed that the increasing of excitation radiation energy hv>E₀ (E₀ is pseudogap width) changes a shape, intensity, and position of Raman peaks of g-As₄₀Se₆₀. The structure and vibration spectra of some As-Se clusters were calculated applying the ab initio method. In order to elucidate structural features of g-As₄₀Se₆₀, we combined the experimental Raman data and theoretical calculations.
format Article
author Mateleshko, N.
Mitsa, V.
Veres, M.
Koos, M.
Stronski, A.
spellingShingle Mateleshko, N.
Mitsa, V.
Veres, M.
Koos, M.
Stronski, A.
Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering
Semiconductor Physics Quantum Electronics & Optoelectronics
author_facet Mateleshko, N.
Mitsa, V.
Veres, M.
Koos, M.
Stronski, A.
author_sort Mateleshko, N.
title Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering
title_short Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering
title_full Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering
title_fullStr Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering
title_full_unstemmed Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering
title_sort investigation of nanophase separation in ir optical glasses as₄₀se₆₀ using resonant raman scattering
publisher Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
publishDate 2004
url https://nasplib.isofts.kiev.ua/handle/123456789/118169
citation_txt Investigation of nanophase separation in IR optical glasses As₄₀Se₆₀ using resonant Raman scattering / N. Mateleshko, V. Mitsa, M. Veres, M. Koos, A. Stronski // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2004. — Т. 7, № 2. — С. 171-174. — Бібліогр.: 19 назв. — англ.
series Semiconductor Physics Quantum Electronics & Optoelectronics
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AT veresm investigationofnanophaseseparationiniropticalglassesas40se60usingresonantramanscattering
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first_indexed 2025-11-24T04:19:47Z
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fulltext 171© 2004, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine Semiconductor Physics, Quantum Electronics & Optoelectronics. 2004. V. 7, N 2. P. 171-174. 1. Introduction Photo-induced effects in amorphous chalcogenide semi- conductors are widely investigated as both fundamental processes of structural transformations in amorphous sol- ids and promising applications in optoelectronics due to the related changes of optical parameters [1]. Among chalcogenide glasses, As-S and As-Se systems are models for studying the structure and photoinduced phenome- na in non-crystalline semiconductors. Much efforts have been devoted to study these materials by various tech- niques, for instance, Raman spectroscopy. A usage of excitation radiation of different energies causes some changes in the Raman peak position and their shape. Phenomena of resonant behavior of Raman bands at en- ergies less than pseudogap width in As-S system glasses can be explained by creation of As-As and S-S bonds in the matrix structure [2]. Theoretical calculations [3] and X-ray photoelectron spectroscopy (XPS) experiments [4] suggest that even in stoichiometric As40Se60 glasses, there are wrong As-As and Se-Se bonds. So, it is interesting to investigate resonant Raman spec- tra of g-As40Se60 at excitation energies hν < E0 and hν > E0. 2. Experimental technique The technique of glass synthesis is described in [5]. Raman spectra of As40Se60 glasses were measured by RENISHAW SYSTEM 1000 Raman spectrometer with CCD (Charge Coupling Device) detecting cell. Raman scattering was excited by a diode laser with the wavelength 785 nm and output power 25 mW and a Spectra Physics Model 168 (Ar) laser with the wavelength 488 nm and output power 1W. The spectra were measured in a back scattering geom- etry. An output power was restricted by filters to avoid a photoinduced structural changes. Raman spectrum excited by 1060 nm wavelength were taken by Fourier Transformation (FT) BRUKER IFS55 IR spectrophotometer with FRA-106 accessory, output power 90 mW [6]. For previous calculations of geometry and Raman spec- trum, a linear As2Se3 cluster was chosen. Calculations were carried out by the ab initio Hartree-Fock method with 6�31 basis set, GAMESS (US) software [7]. Hydrogen atoms satu- rated the end atoms. Geometrical parameters and vibrational spectra of As2Se5, As4Se6, and As6Se9 clusters were calculated by the ab initio Hartree-Fock method with LANL2DZ, GAUSSIAN-94 program packages [8]. PACS: 61.43.-j, 78.30.-j Investigation of nanophase separation in IR optical glasses As40Se60 using resonant Raman scattering N. Mateleshko1, V. Mitsa1, M. Veres2, M. Koos2, A. Stronski3 1Uzhgorod State University, Department of Solid State Electronics 32, Voloshin str., 88000 Uzhgorod, Ukraine, E-mail: mitsa@univ.uzhgorod.ua 2Research Institute for Solid State Physics and Optics H-1121 Budapest Konkoly Thege M. u. 29-33. Hungary 3V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine 41, prospect Nauky, 03028 Kyiv, Ukraine Abstract. Resonant Raman spectra of stoichiometric glass (g) g-As40Se60 have been investi- gated. It was observed that the increasing of excitation radiation energy hν > E0 (E0 is pseudogap width) changes a shape, intensity, and position of Raman peaks of g-As40Se60. The structure and vibration spectra of some As-Se clusters were calculated applying the ab initio method. In order to elucidate structural features of g-As40Se60, we combined the experimental Raman data and theoretical calculations. Keywords: chalcogenide glasses, resonant Raman spectra Paper received 01.03.04; accepted for publication 17.06.04. 172 SQO, 7(2), 2004 N. Mateleshko et al.: Investigation of nanophase separation in IR optical glasses ... 3. Results and discussions Recent investigations have shown that shape and posi- tion of Raman peaks in g-As2S3 depends on excitation wavelength. The energy of excitation radiation can be greater or lesser than the pseudogap width that causes a shift of maxima positions [9] by electronic processes in- fluence. Fig. 1 shows Raman spectra inherent to As2Se3 glass excited with light of different energies. The wavelengths are 1060, 785, and 488 nm with energies 1.17, 1.58, and 2.54, respectively. The latter energy value exceeds the pseudo bandgap energy of g-As2Se3 (E0 = 1.9 eV [10]). Raman spectra obtained using lasers with wavelengths 1060 and 785 nm, hν < E0, comprise one broad band peaking at 227 cm�1. Raman spectra of crystalline (c) c-Se (Fig. 2) and amorphous (a) a-As (Fig. 2) have intensive bands at 235, 250 and 227, 252 cm�1, respectively. So, it is impos- sible to give an exact identification of structural units (s.u.) of g-As40Se60 by comparing the Raman spectra of g-As2Se3, c-Se and a-As. Some authors [11] suppose that it is enough to coincide the calculated vibration frequency of AsSe3 �molecule� with experimental position of the Raman spectra band for assignment of maxima at 230 cm�1 to AsSe3/2 s.u. vibration. But Raman scattering by bulk AsxS1�x glasses shows that the vibrational modes of As4S4 monomers appear first near x = 0.38, and their concentration sharply increases with increasing x, sug- gesting that the stoichiometric glass (x = 0. 40) is intrin- sically phase separated into small As-rich (As4S4) and large S-rich clusters [12]. Since synthesis procedures of g-As2S3 and g-As2Se3 are similar, it is possible that the latter may contain not only AsSe3/2 s.u. but AsSe4/2 and Se-Se inclusions. Really, for a laser with hν < E0 sensi- tive to the structural fragments of small sizes, Raman spectra of g-As2Se3, if using λ = 488 nm, differ from the spectra taken at λ = 1060, 785 nm (Fig. 1). Raman spectra of g-As40Se60 taken at λ = 488 nm contains the broader band with maxima at 230 cm�1. On broad maxim it is clearly seen peaks at 220 and 228 cm�1 that can be assigned as assymetric and symmetric vibra- tions of AsSe3 pyramid. From high-frequency side there is a shoulder at 276 cm�1 that can be a mode of As-Se bond vibrations in As4Se4 molecules (Table 1). The band broadened from low-frequency side (up to 200 cm�1) at λ = 488 nm can be ascribed to the presence of As-As bonds in As3/3 s.u. Similar situation was observed in the reso- nant Raman spectrum of g-As40S60 [13]. As can see from Fig. 1 broaden low frequency side of Raman line of g-As40Se60 excited with λ = 488 nm has shoul- ders at 190 and 208 cm�1 that are most intensive bands at Raman spectra of crystalline As4Se4 (Table 1) and may be assigned to vibrations of As-As bonds [15]. A frequency 200 300 400 �2 0 2 4 6 8 10 12 227 l=488 nm l=785 nm l=1060 nm 285 276 262 254 245 239 228 220 208 197 190 180 166 �1 Fig. 1. Raman spectra for g-As40Se60 excited with light of differ- ent wavelengths indicated. �1 50 100 150 200 250 300 350 0,0 0,2 0,4 0,6 0,8 1,0 c-Se a-As Fig. 2. Raman spectra of crystalline Se and amorphous As taken at λ = 785 nm. Table 1. Band positions and their assignment in Raman spec- tra of crystalline As4Se3 [14] and As4Se4 [15]. c-As4Se3 [12] c-As4Se4 [13] À1 280 (m.) ν As-As 275 (w.) ν As-Se 266 (m.) As-Se 248 (very s.) ν As-Se 256 (s.) As-Se 235 (m. w.) ν As-Se 242 (s.) ν As-Se 216 (m. w.) ν As-Se 236 (w.) ν As-Se 207 (s.) ν As-As 188 (w.) Se-As-Se, 190 (s.) ν As-As As-Se-As 196 (s.) As-As 152 (w.) δ As-Se-As 166 (w.) 140 (w.) 144 (m.) δ As-Se-As s � strong, m � medium, w � weak, sh � shoulder N. Mateleshko et al.: Investigation of nanophase separation in IR optical glasses ... 173SQO, 7(2), 2004 position of shoulder at 197 cm�1 in Raman spectra of g-As40Se60 coincides with one of more intensive Raman band of crystalline As4Se3 (Table 1). The shoulders that appear on the lowfrequensy side of main band of g-As40Se60 at irradiation with wave energy 2,54 eV may be due to the exciting of homopolar As-As bonds. Indeed it is impossible to give an exact assignment of these bonds to molecules As4Se4(3) on Raman data. Such indefinition exists at interpretation of high fre- quency side of main Raman band of g-As40Se60. Existence of shoulder at 254 cm�1 may be related to the presence both of Se-Se bonds in free Se (Fig. 2) and As-Se bond vibra- tions of As4Se3 molecule. The bend at 245 cm�1 may exist due to As-Se bonds of As4Se4 molecule. For g-As2S3 Kawazoe et al. [16] have reported reso- nance enhancement of Raman peaks sterming from As-As and S-S homopolar bonds, which are assumed to provide band tail states of the valence band. So, we can made a conclusion that structural study needs methods which may give exact information about bond types. For example we used [17] x-ray photoelec- tron spectroscopy for As-GeS2 system. Using short wavelength laser radiation to excite the Raman signal gives a series of low intensity bands in the range above 300 cm�1 (Fig. 1). An assignment of these bands can be made using quantum-chemical calculations. First of all, we choose a simple chain cluster As2Se3. Geometry of this cluster is shown in Fig. 3. To keep the atom valency, hydrogen atoms were used. Schematic geometry of the following clusters are shown in Fig. 5 An important feature of As2Se5 cluster is Se-Se bonds at the ends of clusters. The ends of As4Se6, As6Se9 clus- ters were closed by the double Se bond. A calculated freguencies at 300 cm�1 may be assigned to vibrations of Se-Se bonds at the cluster ends (Fig. 6). The vibrations of Se atoms at the ends of As2Se3, As4Se6 and As6Se9 clusters have frequency at 360 cm�1 (Fig. 6). So, the low intensive bands at 300 and 350 cm�1 in the Raman spectra of g-As40Se60 may be related to the vibra- Se Se Se As As Fig. 3. The optimized geometry of As2Se3 cluster (hydrogen atoms are not shown). Fig. 4. Raman spectra of As2Se3 cluster. �1 100 200 300 400 500 0.00 0.05 0.10 0.15 0.20 0.25 0.30 As Se Se Se Se Se Se Se Se Se Se Se Se Se Se Se Se Se As As AsAs As As As As As As As As Se Se Se Se As Se As Se 2 5 6 9 4 6 Fig. 5. The optimized geometry of As2Se5, As4Se6, As6Se9 clusters. Fig. 6. Vibration spectra of clusters. �1 100 150 200 250 300 350 0.0 0.2 0.4 0.6 0.8 1.0 As 6Se9 100 150 200 250 300 350 0.0 0.2 0.4 0.6 0.8 1.0 As4Se6 100 150 200 250 300 350 0.0 0.2 0.4 0.6 0.8 1.0 As2Se5 174 SQO, 7(2), 2004 N. Mateleshko et al.: Investigation of nanophase separation in IR optical glasses ... tions of Se-Se and As-Se ends, respectively. The same situation was observed for another cluster types Ge-S and As-S [18, 19]. So, excitation of the Raman signal by energy hν > E0 makes spectra more informative, which allows to reveal s.u. As3/3, As2Se4/2, Se2/2 in g-As40Se60 structure. Acknowledgements Authors wish to acknowledge Prof. F. Billes and P-G. S. R. Holomb for calculations and discussions. This work was supported by the Grant No. M/467- 2003 and Grant No. 29/48-2001 (Ministry of education and science of Ukraine and Hungarian Science and Tech- nology Foundation). Reference 1. S. Kokenyesi, J. Chikai, P. 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