Z.G. Ivanova

Thermomechanical and structural characterization of GeSe2–Sb2Se3–ZnSe glasses

Abstract On the basis of thermal and physicochemical properties of multicomponent GeSe 2 –Sb 2 Se 3 –ZnSe glasses, several microstructural characteristics such as glass-forming ability ( K gl ), compactness ( C ), micro-voids volume ( V h ), their formation energy ( E h ), module of elasticity ( E ) and apparent activation energy of glass transition ( E a ) have been determined. Their compositional dependencies have shown that all these parameters increase at higher GeSe 2 content, remaining almost constant in the range of 63–72 mol% GeSe 2 . The distribution of the corresponding structural units has been discussed on the basis of Raman scattering data.

On the structural phase transformations in GexSb40−xSe60 glasses

Abstract A correlation between the observed peculiarities in the variation of some physicochemical parameters of Ge x Sb 40− x Se 60 ( x =10, 20, 25, 27, 32, 35) glasses and their structure has been found by studying the average coordination, Z . In particular, the composition dependences of the microhardness and its derivative characteristics (micro-voids volume, their formation energy, and module of elasticity) have shown an extremal behaviour at Z =2.65–2.67. The results on the density and compactness have also indicated the occurrence of an additional feature at the Ge 27 Sb 13 Se 60 composition having Z =2.67. Furthermore, the increase of the intensity ratio between homopolar and heteropolar Raman bands with Z is accompanied by a break at Z =2.65–2.67. The observed Raman modes have been related to the corresponding bond vibrations and the structure of the glasses studied has been specified. Accepting a tendency towards strong chemical ordering for these glasses, the distribution of the possible chemical bonds has been determined. The obtained defective bond population is confirmed by the experimental Raman data.The established peculiarities at Z =2.65–2.67 have been attributed to structural rearrangements of the backbone of the glasses.

A Zn(II) ion-selective electrode based on chalcogenide As2Se3–Sb2Se3–ZnSe and GeSe2–ZnSe–ZnTe glasses

Zn(II) ion-selective electrodes with chalcogenide glassy As2Se3–Sb2Se3–ZnSe and GeSe2–ZnSe–ZnTe membranes were developed. Basic analytical characteristics such as stability, linearity, slope of the electrode function, limits of detection, effect of pH on the electrode potential and response time were studied with varying glass compositions. A structural mechanism for explanation of the dependencies obtained is suggested.

New IR-transmitting chalcohalide glasses

Abstract The glass-forming region in the GeS 2 GaI system has been determined and its limits are 32 at.% Ga and 60 at.% I. The basic physicochemical parameters (glass transition temperature, density and microhardness) of the glasses have been measured. They are transmitting in the mid IR-region up to ∼ 20 μ m. A photobleaching effect in thin films has been observed, and a reversible shift of the optical absorption edge after combined treatment by thermal annealing and ultraviolet exposure has been established.

On the glass formation in the semiconducting -Se-ZnTe, Se-Se-ZnSe and -ZnTe-ZnSe systems

The glass-forming regions in the -Se-ZnTe, Se-Se-ZnSe and -ZnTe-ZnSe chalcogenide systems have been determined. The temperatures of phase transformations (the glass transition, crystallization and melting), the density and the microhardness have been studied. The crystalline phases which can be formed in these glasses have been specified. The established correlation between the properties and the composition has been explained with respect to the specific roles of the compounds involved. The results obtained have been compared with those for the similar ternary -Se-ZnSe system.

Topological transition and rigidity percolation in Ge-Se(S)-Cd glasses

Abstract The glass-forming region in the Ge–Se–Cd system has been determined, where up to 12 at.% Cd can be introduced into the binary Ge 20 Se 80 composition. Specific features in the compositional dependence of the density, d , and microhardness, H m , on the average coordination number, Z , have been found. In particular, two extrema have been observed at Z =2.4 and Z =2.68, both in bulk glasses and in amorphous films of the Ge x Se 98− x Cd 2 family, but the effects are less in the latter case. The same regularities have also been established for the glassy Ge–S–Cd system. The results obtained are compared with those for the previously studied Ge–Se–Fe system. They are discussed on the basis of rigidity percolation concepts and in terms of topological structural transitions in chalcogenide glasses.

Influence of Ga on the luminescence efficiency of Er-doped Ge–S–Ga glasses

Photoluminescence (PL) spectroscopy has been applied to a series of Er-doped (GeS2)100−x(Ga2S3)x glasses with varying x (0, 10, 20, and 25 mol %) and at a constant content of 0.6 mol % Er2S3. The PL band at 1534 nm, excited with 1064-nm light, has been characterized. The corresponding transitions in the Er3+ energy-level diagram have been specified by deconvolution of the spectra. It has been found that the PL intensity of the glasses becomes more definitive at x>10, and increases by about 30 times with the addition of 25 mol % Ga2S3.

Photoinduced transformations in amorphous GeS2-based thin films☆

Abstract A study of photoinduced optical changes in some new GeSBi and GeS2GaI amorphous compositions has been performed. The known glass-forming ability in the GeSBi system has been extended by obtaining glassy (GeS2)100 - xBix (x = 4, 8, 12) phases. The observed thermo-bleaching effect in the thin films is significantly more pronounced than the photo-bleaching induced by ultraviolet exposure. Maximum values of the relative shift, Δλ, in the optical absorption edge for GeS2GaI films have been found at a GeS 2 Ga ratio of 3 and an I content up to 30 at.%. Summarizing all of the results concerning amorphous GeS2-based thin films, with additions of Bi, Ga and/or I, it can be concluded that the largest photoinduced optical transformations have been observed for Ga-containing samples.

Thermal Stability and Optical Activity of Erbium Doped Chalcogenide Glasses for Photonics

The glass transition and crystallization temperatures (T g , T c ), heat capacity, thermal stability and glass uniformity of GeSGa, GeSeGa, Ge(SeTe)Ga chalcogenide glasses doped with Er3+ by the addition of Er2S3 have been investigated by conventional differential scanning calorimetry (DSC) and Temperature-Modulated DSC (TMDSC). While some of the glasses have two crystallization peaks, these glasses were nonetheless optically actively and uniform. Essential optical properties have been evaluated, such as the photoluminescence (PL) intensity and lifetime as a function of the glass composition. We present typical results to emphasize some of the important characteristics of these systems and discuss trends within a glass system; and also highlight differences between glass systems.