As-Se System Research Articles

Glass transformation, heat capacity and structure of ASxSe1−xglasses studied by modulated temperature differential scanning calorimetry experiments

Abstract The recent novel temperature modulated differential scanning calorimetry (MDSCTM TA Instruments Inc. USA) technique has been applied to the measurement of the thermal properties of chalcogenide glasses of the As-Se system in the glass transition region. All samples in this work were given the same thermal history by heating to a temperature above the glass transition, equilibrating and then cooling at a rate of 5°Cmin1 to a temperature of 20°C. The reversing and non-reversing heat flows through the glass transformation region during both heating and cooling schedules were measured and the values of the parameters Tg , ΔH, Cp and ΔCp , which characterize the thermal events in the glass transition region, were determined. The ability to determine the reversible heat flow in MDSC enables an accurate measurement to be made of the true heat capacity (that normally associated with reversible heat flow). This could not be done hitherto in conventional thermal analysis where the detected heat flow is the...

P-T diagram in the As-S system

Abstract Chalcogenide glasses in the system As-S are candidates for very low loss fiber-optic materials. In order to modulate physical properties of such glassese by wellaimed pressure variation the knowledge of the P-T diagram is a precondition. Therefore the aim of this investigation was to cheque the energy-dispersive X-ray diffraction method for low symmetry materials like Realgar (AsS) in order to elaborate P-T diagrams in a time reducing technique.

Photostructural changes in bulk chalcogenide glasses: An EXAFS study

EXAFS studies of reversible photostructural changes in bulk As and Ge chalcogenide glasses have been performed. The compositions studied were Ge33Se67, Ge40Se60, Ge40S60, As40S60 and As43S57. The magnitude of the photostructural change in both germanium and arsenic systems is larger in off-stoichiometry samples. In the AsS system the structural change is characterised by an increase in the AsSAs bond angle, whereas in the GeS (Se) systems a bond-breaking mechanism dominates. These data are consistent with neutron scattering and electron spin resonance data.

Transient properties of photo-excited conducting carriers in a disordered As-Se system

The time resolved photoconductivity of an As-Se system after excitation of the carriers by monochromatic light is studied by pulsed xenon excitation and also by the correlation method with the quasi-random signal. Non-exponential time decay of the photoconductivity was observed. The character of the decay curves depends strongly on the exciting photon energy and depends slightly on the pulse repetition time. These features should be related closely with the various kinds of structural disorder and distribution of the localized levels in the forbidden energy gap. The decay curve is explained by the superposition of processes with different decay times. From the analysis of the thermal activation hopping process, the distribution of trap levels is estimated.

Model of photoinduced changes of optical properties in amorphous layers and glasses of Ge-Sb-S, Ge-S, As-S and As-Se systems

Photoinduced changes of transmittance /Δt/ and reflectance /Δr/ of thin layers, glasses and glassy powders of systems Ge-Sb-S, Ge-S, As-S and As-Se were studied. For explanation of experimental results a model is suggested which implies both the redistribution of chemical bonds and the compactness of the structure.

Nonsteady photoconductivity of layers of glass of the As-Se system

This article examines experimental results from a study of impulsive photoconductivity in layers of glasses of AsxSe100−x (30<x<-@#@ 60). It was found that thermal and laser treatment (thermo- and photostructural changes) affect the character of relaxation processes in photoconduction in freshly prepared layers. It was also established that both annealing at temperatures near the softening point of the glass and laser irradiation with quantum energies exceeding the width of the forbidden band are accompanied by a change in the recombination lifetime of nonequilibrium carriers. It is concluded on the basis of empirical data that an efficient recombination channel complementary to the main channel (tunnel transition of the type 2D0→D++D−) is present in freshly prepared layers. The latter is present in annealed layers. The additional recombination channel is related to the existence of homopolar bonds in binary arsenic selenides and is proven to exist by data on the effect of composition on photocurrent relaxation.

New analytic method for investigation of the distribution of bonds in As-S system

This paper describes a simple analytical method enabling the determination of the concentration of As-As bonds. We have proved that immediately after evaporation the samples contain at least 32% of As-As bonds from the total number of bonds by which arsenic is bound to its neighbourhood. Their content markedly decreases after annealing and illumination.

STUDY ON THE SHORT RANGE STRUCTURES OF BINARY AMORPHOUS ARSENIC-SELENIUM SYSTEM BY EXAFS

The EXAFS of amorphous semiconductor a-As2Se3, a-AsSe, a-As0.05 Se0.95 and a-As2Se3) after annealing at different temperatures lower than Tg are measured by 12 kW rotating anode X-ray diffraction equipment. Analyses of the determined radial structural functions shows that although the short range structure of a-As2Se3 is very similar to that for crystalline As2Se3, some changes take place in its radial structural function after annealing. The structural relaxation in a-As2Se3, quenched from melt, has also been observed. The short range structures for different components of As in binary As-Se system seem to be different.

Chalcogenide glass fibers for mid-infrared transmission

Chalcogenide glass fibers for mid-infrared transmission have been fabricated in As-S, As-Ge-Se, and Ge-S glass systems using high purity materials. The preparation of unclad, Teflon FEP clad, and chalcogenide glass clad fibers and their transmission loss characteristics are reported. It is found that appropriate glass compositions for drawing low-loss fibers are limited to the narrow ranges in the glass-forming regions. The minimum losses obtained are 35 dB/km at 2.44μm for As 40 S 60 unclad fiber, 182 dB/km at 2.12 μm for As 38 Ge 5 Se 57 unclad fiber, and 148 dB/km at 1.68 μm for Ge 20 S 80 unclad fiber. It is shown that hydrogen impurity absorptions and short-wavelength weak absorption tails seriously enhance loss in the fibers. It is also suggested that ultralow loss cannot be achieved due to the existence of the weak absorption tail. However, it is expected that the chalcogenide glass fibers can be used in short fiber-length applications such as in the remote monitoring and delivery of CO laser radiation. This is due to their wide operating wavelength ranges of 0.9-6\mu m for As-S, 1.3-9\mu m for As-Ge-Se, and 0.8-5\mu m for Ge-S, in which losses can be reduced to below 1 dB/m.

Kinematic viscosity of As xSe 1− x glass forming liquids

The kinematic viscosity behaviour of As x Se 1− x molten chalcogenides is relatively well described by an Arrhenius equation: ν = ν 0 exp( W/ kT), for x between 0 and 0.8. The ν( x) and W( x) evolutions suggest that all these liquids present a polymeric structure, even outside the easy glass forming region. The tendency of atoms to form separate molecules, previously observed in the As-S system, remains small and only causes a slight inflexion in the ν( x) and W( x) isotherm curves near x = 0.5.

The influence of defects generated during densification on the properties of the As-Se system

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Raman Scattering in Amorphous As-Se System

Raman spectra of amorphous AsxSe1-x system (0≤x≤0.5) were measured and the spectra were interpreted with the molecular model of Lucovsky and Martin. In the Se-rich region the observed Raman spectra are well reproduced by the superposition of the Raman intensity of pure Se, As2Se3 and As2Se4 in proportion to x. In the As-rich region the Raman spectrum at x=0.45 is well described by the average of those at x=0.4 and 0.5. The amorphous state of AsxSe1-x for 0<x<0.4 is shown to be composed of a Se8 ring, Sen chain, AsSe3 unit and As2Se4 unit. In the As-rich region, the local structure change due to the substitution of As and Se is small.

A note on the Raman spectra and structure of As x S 100−x (x ⩾ 40) glasses

A recent paper in this journal by Slade and Zallen states that the present authors have suggested that actual microcrystals of β-As 4S 4 are present in vapour-deposited films of As 2 S 3. This is a mistaken interpretation of our previous work and in correcting the record we make some additional observations on the Raman spectra and structure of glasses in the As-S system. It is concluded that the Raman data is inconclusive on the existence, or otherwise, of phase-separated crystals.

Chalcogenide thin films for laser-beam recordings by thermal creation of holes

The shapes of holes thermally created by a laser beam in thin films of wide range of materials are studied. The most cleanly shaped holes, which measure up to recent requirements for direct-read-after-write video recordings by submicron dots, are obtained in some compositions of amorphous chalcogenide thin films such as As-Te system, Ge-Te system, As-Se system, Ge-Se system, and Sb-S system thin films. The experiments clarify several important conditions helpful in obtaining cleanly shaped holes. The most important condition is that the viscosity of the material in liquid or softened state should be high. The required incident laser-beam power for recording in an As-Te system thin film on a polymethyl methacrylate substrate rotating at 1800 min−1 is about 10 mW. Addition of Se to the As-Te system thin films greatly increases film stability. A signal-to-noise ratio of about 45 dB is obtained in reproduced color video signals.

Etude des verres formes dans le ternaire EuAsS

From the glasses of the binary As-S system, a large region of ternary glasses is observed in the Eu-As-S system. The thermal behaviour, the magnetic susceptibility and the Raman and infrared absorption spectra show that europium is always in the divalent state, in contrast with the ternary phase diagram in which compounds of trivalent europium are present.

Positron annihilation in point defects of the glassy As-Se system

physica status solidi (a)Volume 48, Issue 2 p. K169-K173 Short Note Positron annihilation in point defects of the glassy As-Se system O. K. Alekseeva, O. K. Alekseeva Institute of Chemical Physics, Academy of Sciences of the USSR, MoscowSearch for more papers by this authorV. I. Mikhailov, V. I. Mikhailov Institute of Chemical Physics, Academy of Sciences of the USSR, MoscowSearch for more papers by this authorV. P. Shantarovich, V. P. Shantarovich Institute of Chemical Physics, Academy of Sciences of the USSR, MoscowSearch for more papers by this author O. K. Alekseeva, O. K. Alekseeva Institute of Chemical Physics, Academy of Sciences of the USSR, MoscowSearch for more papers by this authorV. I. Mikhailov, V. I. Mikhailov Institute of Chemical Physics, Academy of Sciences of the USSR, MoscowSearch for more papers by this authorV. P. Shantarovich, V. P. Shantarovich Institute of Chemical Physics, Academy of Sciences of the USSR, MoscowSearch for more papers by this author First published: 16 August 1978 https://doi.org/10.1002/pssa.2210480261Citations: 23AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume48, Issue216 August 1978Pages K169-K173 RelatedInformation

Induced anisotropy in a glassy material of the As-S system

The anisotropic properties of some chalcogenide glassy semiconductors changed under the influence of temperature and laser radiation of 0.63 μ wavelength. The induced anisotropy was found to be a function of the composition and previous history of a sample, and was associated with the appearance of nuclei of a new phase as a result of preliminary annealing.

Magnetic susceptibility of glassy As-Se system

Magnetic susceptibility of glassy As-Se system

Thermal processing and light sensitivity of thin layers of glasses of the As-Se system

Thermal processing and light sensitivity of thin layers of glasses of the As-Se system

The photoluminescence properties of glasses in the As-Se system

Abstract From photoluminescence (PL) studies of the As-Se system it is found that the PL intensity is proportional to As concentration for compositions ranging from 0·3 at.% As to As2Se3. Other PL properties are essentially unchanged. It is argued that this behaviour provides good evidence that the PL recombination centre is an As broken bond.