Papers by Keyword: Chalcogenide Glasses

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Authors: Kameshwar Kumar, Nagesh Thakur, S.C. Katyal, Pankaj Sharma
Abstract: In the present communication, a study was made of the compositional variation of physical properties: average coordination number (), average number of constraints (Ncon), number of lone-pair electrons (L), mean bond energy (), cohesive energy (CE), average heat of atomization (Hs), glass transition temperature (Tg), density (ρ) and theoretical energy gap (Eg) for Te15(Se100-xBix)85 (x = 0, 1, 2, 3, 4, 5at%) glassy alloys. The mean bond energy and the cohesive energy have been calculated using the chemical bond approach (CBA). The glass transition temperature was calculated using the Tichy-Ticha approach, and has been found to increase with Bi content. The mean bond energy is found to be proportional to the glass transition temperature and the average coordination number. It has been found that the average coordination number, average number of constraints, mean bond energy and density increase, whereas the cohesive energy, average heat of atomization and theoretical energy gap decrease with increasing Bi content in Se-Te alloys.
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Authors: Mykhaylo Shpotyuk, Dmytro Chalyy, Oleh Shpotyuk, Mihail Iovu, Andrzej Kozdras, Sergii B. Ubizskii
Abstract: Principal possibility of the using of chalcogenide glasses (on the example of Ge18As18Se64) as active media for temperature sensors is considered in this work. Differential scanning calorimetry testing of the investigated glasses shown that 2 years of natural storage does not lead to the drift of their DSC-parameters (glass transition temperature and endothermic peak area). Investigation of the temperature dependence of optical transmission spectra shows the linear character of optical band-gap changes with a temperature. Temperature sensitivity index β for Ge18As18Se64 is estimated to be equal to the ~1.2·10-3 eV/°C.
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Authors: Husain Mushahid, Raman Swati
Abstract: The present research work is focused on fabricating the chalcogenide glass optical waveguides keeping in mind their application in optical communication. The propagation loss of the waveguides is also studied at three different wavelengths. The waveguides were fabricated by dry etching using ECR Plasma etching and the propagation loss is studied using Fabry-Perot technique. The waveguides having loss as low as 0.35 dB/cm at 1.3m is achieved. The technique used to fabricate waveguide is simple and cost effective.
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Authors: S.R. Lukić, D.M. Petrović, V.B. Petrović, D.D. Petrović
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Authors: Yong Gyu Choi
Abstract: Ga K-edge EXAFS spectra have been analyzed to elucidate the local coordination structure of Ga in two representative selenide Ge-As-Se and Ge-Sb-Se glasses all doped with Pr. Gallium turned out to be coordinated with 4 Se atoms in its first neighboring shell. This implies that Ga does not follow the 8-N rule associated with the short-range order structures of typical covalent glasses, further indicating there being more ionic-bond nature in the Ga-Se bonds compared to other heteropolar chemical bonds in the selenide glasses. This is decisive for the Pr3+ ions to be incorporated in the selenide glasses. In this case, the GaSe4 units can be electrically neutralized by the doped Pr3+ ions that act as a charge compensator. As such, inside the selenide glasses, distributions of Pr3+ ions and the Ga tetrahedral units are closely correlated. Spectroscopic properties of rare earths embedded in these Ga-containing selenide glasses thus can be explained in connection with the proposed role of Ga.
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Authors: Rajneesh Kumar, Pankaj Sharma, Virsingh S. Rangra
Abstract: In the present work, DSC and FTIR study of the of Se92Te8-xSnx ( x=0, 2 and 4) glassy samples has been studied. FTIR spectra was taken in wavelength region 50-600 cm-1. The parameters like theoretical wave number and activation energy of glass transition and crystallization has been calculated by Kissinger’method and Augis and Bennett’approximation. With the addition of Sn, Far-IR spectra shift toward high frequency side and new bands starts appearing in the spectra. The Sn atom appear to substitute for the selenium atoms in the outrigger sites due to large bond formation probability. Activation energy of glass transition increases with Sn addition while for crystallization, it also increases except at x=1.
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Authors: B. Arcondo, M.A. Ureña, A. Piarristeguy, M. Fontana
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Authors: M.L. Trunov, Sergey N. Dub, R.S. Shmegera
Abstract: The combination of depth-sensing indentation and band-gap illumination has been used to study the photoplastic effect (the reversible influence of light on the flow stress, hardness, and plasticity) in chalcogenide glasses on a nanoscale. The prominent photoplasticity of thin As-Se films has been revealed through deviations in the shape of load-displacement curves during nanoindentation under light illumination from those ones which have been observed for the material in the darkness. The photoinduced changes in static mechanical properties such as nanohardness and elastic (Young’s) modulus have been determined. The highest photoplasticity changes are achieved for As20Se80 films while their photodarkening is the lowest.
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Authors: A.V. Semencha, M.V. Kurushkin, V.A. Markov
Abstract: In the present work, glasses of the As-S-I system have been synthesized, the region of glasses stable in moist air has been investigated, the properties of the glasses have been determined.
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Authors: K. Ramesh, Pumlianmunga, R. Venkatesh, N. Naresh, E.S.R. Gopal
Abstract: Chalcogenide glasses switches from a high-resistance (OFF) state to a low-resistance (ON) state at a threshold voltage (Vth) under high electric fields. This electrical switching is of two types: (i) Threshold switching and (i) memory switching. Threshold switching device revert back to the OFF state immediately upon the removal of the applied voltage, whereas a memory device retains the ON state even after the removal of the applied voltage. Due to Joule heating, a filament is formed between the electrodes and the current is confined within this filament and there is an increase in current density. This increases the temperature inside the filament and there is a transition from high resistive amorphous/glass phase to a low resistive crystalline phase in memory switching materials. In the threshold switching glasses electronic processes like space charge, Poole-Frenkel effect, etc., are responsible. The structural transitions are irreversible whereas the electronic processes are reversible and hence the threshold glasses regain their original state (OFF) and memory glasses remain in the ON state.Interestingly, differential scanning calorimetric studies (DSC) show that both the threshold and memory switching glasses exhibit crystallization (structural transition). Accordingly, glasses which crystallize upon heating should exhibit memory switching behaviour. But the switching experiments indicate that among the glasses which undergo structural transition (crystallization) some show threshold switching and some show memory switching. To understand this, Cu-As-Se, Al-As-Te, Ge-As-Se-Te, Al-As-Se-Te glasses were thermally crystallized under vacuum in two ways: (i) by annealing at their respective crystallization temperatures (Tc) and (ii) heated up to their melting temperatures (Tm) and cooled back to room temperature. Interestingly, most of the threshold switching glasses shows amorphous nature or a huge amorphous background with crystalline peaks when cooled from their melting temperatures. The memory switching glasses crystallize in both the cases.We propose that both threshold and memory glasses undergo phase change and the crystalline phases formed from the melt state are responsible for switching to occur. Hence, at the time of switching the sample in between the electrodes undergo phase change by glass → melt → crystal transformation and not by the direct glass → crystal transformation.
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