Synthesis, electrical properties, and structural features of copper-containing chalcogenide films produced by the chemical deposition method

Multicomponent copper-containing CuI-AsI₃-As₂Se₃ and CuI-Sb₃I-As₂Se₃ chalcogenide films were produced by chemical deposition from solutions of chalcogenide glasses in n-butylamine and their electrical conductivity was studied. It was shown that the electrical properties of chalcogenide glasses and films based on these glasses have the same values within experimental error. It was found sing Mossbauer spectroscopy that antimony atoms are in the Sb(III) state in the environment of three selenium atoms, and copper ions in the Cu(I) state and are surrounded by iodine atoms. The chalcogenide films can be used to fabricate ion-selective electrodes sensitive to copper cations.     

Processing and characterization of new passive and active oxysulfide glasses in the Ge-Ga-Sb-S-O system

New passive and active oxysulfide glasses have been prepared in the Ge-Ga-Sb-S-O system employing a two-step melting process which involves the processing of the chalcogenide glass (ChG) and its subsequent melting with amorphous GeO₂ or Sb₂O₃ powder. Optical characterization of the oxysulfide glasses has shown that the UV cut-off wavelength decreases with increasing oxygen content. Using Raman spectroscopy, correlations have been made between the formation of new Ge- and Sb-based oxysulfide structural units, the Sb content and the O/S ratio. We demonstrate the successful processing of active rare earth doped oxysulfide glasses by melting the chalcogenide glass with Er₂O₃ and Sb₂O₃ and also by melting the Er³⁺ doped chalcogenide glass with Sb₂O₃. Modification of the emission spectra at 1500 nm of Er³⁺ doped samples with the introduction of oxygen revealed that Er³⁺ most likely exists in dual O- and S-neighbor environments. Finally, the photo-response of these new glasses upon near-IR femtosecond laser irradiation has been investigated as a function of Sb content and O/S ratio and shows that the glasses are photo-sensitive to NIR fs laser light with the magnitude of the photo-sensitivity dependent on the glass’ Sb content and O/S ratio.     

Chemical sensors with chalcogenide glassy membranes

The present review is emphasized on the recent achievements in the application of chalcogenide glasses (ChG) as membrane materials in chemical sensors, microsensors and multisensor systems. The questions concerning material synthesis, sensor designs and the concepts for the potential-generating mechanisms have briefly discussed. Most of the chalcogenide glass-forming systems and compositions investigated as membrane active materials have been summarized, and their analytical characteristics have been considered. The efficiency of chalcogenide-based chemical sensors in the real system analyses, as well as the advantages and disadvantages in their analytical performance have been evaluated and compared with the corresponding polycrystalline analogous.     

Charged particle activation analysis of oxygen in fluoride and chalcogenide glasses used for fiber amplifiers

The proton activation analysis of oxygen was studied in fluoride and chalcogenide glasses used for fiber amplifiers. First, we studied the interfering nuclear reactions from glass matrices to determine the oxygen concentration in these glasses. By using substoichiometric separation for ¹⁸F after irradiation, we found that the oxygen concentration was 12 to 204 ppm in InF₃-based fluoride glass and 0.04% to 0.7% in chalcogenide glass containing sodium. We also discuss the relation between oxygen concentration and optical properties such as the infrared absorption spectrum and fluorescence lifetime.     

Thermodynamic, kinetic and electrical switching studies on Si15Te85−xInx glasses: Observation of Boolchand intermediate phase

An interesting topic for quite some time is an intermediate phase observed in chalcogenide glasses, which is related to network connectivity and rigidity. This phenomenon is exhibited by Si-Te-In glasses also. It has been addressed here by carrying out detailed thermal investigations by using Alternating Differential Scanning Calorimetry technique. An effort has also been made to determine the stability of these glasses using the data obtained from different thermodynamic quantities and crystallization kinetics of these glasses. Electrical switching behavior by recording I-V characteristics and variation of switching voltages with indium composition have been studied in these glasses for phase change memory applications.     

New Sensory Materials Based on Chalcogenide Glasses Containing Zinc,Cadmium, and Manganese Sulfides

New chalcogenide glasses of the system 0.5AgI-(0.5 - x)Sb₂S_3-x MS containing cadmium, man- ganese, and zinc sulfides were obtained. The high purity of these materials and their glassy state were proved by X-ray analysis and X-ray fluorescence energy-dispersive spectroscopy. The impedance of the glasses obtained was measured within a wide range of frequencies, and the dependences of the conductivity on the composition of glasses were studied. New potentiometric sensors based the new glasses were developed, and an electrochemical experiment was carried out.     

Copper ion-selective chalcogenide glass electrodes: Analytical characteristics and sensing mechanism

New copper ion-selective electrodes based on chalcogenide glasses, Cu_xAg_25?xAs_37.5Se_37.5, display high copper(II) ion sensitivity with Nernstian response in the range pCu 1–6, short response time, high selectivity, potential stability and reproducibility. These electrodes are 10–30 times more sensitive in strongly acidic media than crystalline copper ion-selective sensors and are superior to the copper(I) selenide electrode in selectivity and resistance to acids and oxidation. A model is proposed to explain the ion sensitivity of these chalcogenide glass sensors. The sensitivity depends on direct exchange of copper(II) ions between solution and the modified surface layer of the glass. The modified surface layer is formed as a result of partial destruction of the glass network on soaking in solution; its atomic density is 2.0–2.5 times less than that of the original glass. The structural defects and hollows make fast copper(II) ion migration within the modified surface layer possible. Exchange sites in this layer can be formed by both disproportionation and oxidation of copper(I) in the glass network, as well as by diffusion of copper(II) ion from solution in the case of glasses with low copper content. Experimental confirmation of this model is provided by x-ray, photo-electron and scanning Auger electron spectroscopy.     

Processing and characterization of new oxysulfide glasses in the Ge-Ga-As-S-O system

New oxysulfide glasses have been prepared in the Ge-Ga-As system employing a two-step melting process which involves the processing of the chalcogenide glass (ChG) and its subsequent melting with amorphous GeO₂ powder. Optical characterization of the synthesized oxysulfide glasses has shown that the cut-off wavelength decreases with increasing oxygen content, and this has been correlated to results of Raman and infrared (IR) spectroscopies which show the formation of new oxysulfide structural units. X-ray photoelectron spectroscopy (XPS) analysis to probe the bonding environment of oxygen atoms in the oxysulfide glass network, has revealed the preferred formation of Ga-O and Ge-O bonds in comparison to As-O bonds. This work has demonstrated that melting a ChG glass with GeO₂ leads to the formation of new oxysulfide glassy materials.     

Glass transition kinetics and fragility index of chalcogenides from Ag–As–S–Se system

Journal of Thermal Analysis and Calorimetry - The glass transition temperature dependence on a heating rate was investigated by differential scanning calorimetry for chalcogenide glasses from the...     

Absorption and emission spectra in chalcogenide glass of the composition 0.7Ga2S3·0.27La2S3·0.03Nd2S3

Chalcogenide glasses of the composition 0.7Ga₂S₃·0.27La₂S₃·0.03Nd₂S₃ doped by 3 mol% of Nd³⁺ were prepared. The absorption and emission spectra of these glasses were compared to those of commercial ED-2 3.1 wt.% Nd-doped silicate glass. The absorption intensities of Nd³⁺ in chalcogenide glass are higher than in silicate glass due to the increasing covalency of Nd³⁺ in these glasses. Because of the low phonon frequency of the chalcogenide glasses nonradiative relaxations from the ⁴F_{$\text{5}\text{2}$}, ²H_{$\text{9}\text{2}$} to the ⁴F_{$\text{3}\text{2}$} are lower than in other oxide glasses and so fluorescence from this state is observed.     

Electronic structure and the glass transition in pnictide and chalcogenide semiconductor alloys. II. The intrinsic electronic midgap states

We propose a structural model that treats in a unified fashion both the atomic motions and electronic excitations in quenched melts of pnictide and chalcogenide semiconductors. In Part I [A. Zhugayevych and V. Lubchenko, J. Chem. Phys. 133, 234503 (2010)], we argued these quenched melts represent aperiodic ppσ-networks that are highly stable and, at the same time, structurally degenerate. These networks are characterized by a continuous range of coordination. Here we present a systematic way to classify these types of coordination in terms of discrete coordination defects in a parent structure defined on a simple cubic lattice. We identify the lowest energy coordination defects with the intrinsic midgap electronic states in semiconductor glasses, which were argued earlier to cause many of the unique optoelectronic anomalies in these materials. In addition, these coordination defects are mobile and correspond to the transition state configurations during the activated transport above the glass transition. The presence of the coordination defects may account for the puzzling discrepancy between the kinetic and thermodynamic fragility in chalcogenides. Finally, the proposed model recovers as limiting cases several popular types of bonding patterns proposed earlier including: valence-alternation pairs, hypervalent configurations, and homopolar bonds in heteropolar compounds.     

Evidence of network demixing in GeS2-Ga2S3 chalcogenide glasses: A phase transformation study

The information of phase transformation is attained by in situ XRD experiments leading to the knowledge of topological threshold in GeS₂-Ga₂S₃ glasses. The turning point of phase transformation behavior is demonstrated to be glasses containing 14-15 mol% Ga₂S₃. To interpret it a network demixing model is further improved and proposed for the structure of these ternary or quasi-binary chalcogenide glasses. For the nearest-neighbor coordination environment of glass with a transitional composition of 85.7 mol% (6/7) GeS₂·14.3 mol% (1/7) Ga₂S₃, six-coordinated [S₃Ga-X-GaS₃] units (X=S or None) are well isolated by the [GeS₄] structures, which contributes to the decreasing of precipitation of Ga₂S₃ crystals in (100−x)GeS₂-xGa₂S₃ (x≤14.3) glasses corresponding to the experimental evidence of the phase transformation behavior. This scenario of intermediate-range structural order, firstly, includes the arrangement of structural units which is consistent with and provides an atomistic explanation of the compositional evolution of phase transformation behavior in these glasses.     

Simultaneous volume and enthalpy relaxation

The ratio between the relaxed enthalpy and volume (so-called aging modulus, K_a) was expressed in frame of the Tool-Narayanaswamy-Moynihan theory. The common case where various experimental arrangements are used for measuring these quantities was analyzed. It was found that relatively small differences between the conditions of enthalpy and volume relaxation experiments may cause a significant shift of observed K_a value. The sensitivity of K_a modulus to the difference between the enthalpy and volume relaxation conditions is significantly higher in the case of organic polymeric glasses in comparison with silicate and chalcogenide glasses. The reason for such grouping resides in higher values of glass transition temperature and lower values of activation enthalpy of inorganic glasses.     

Short communications

The (3)He activation method for oxygen determination was applied to chalcogenide materials such as Ge(28)Sb(12)Se(60) and Ge(33)As(12)Se(55). Attention was focused on the optimization of the (3)He bombardment energy for non-destructive oxygen determination and the validity of the post-irradiation chemical etch used for removing surface oxygen contamination. The procedure developed was tested on a series of chalcogenide glasses. The detection limit for this non-destructive technique using ~6-MeV (3)He is estimated at ~1 ppm of oxygen.     

Tolerant-to-methanol cathodic electrocatalysts based on organometallic clusters

A new approach to the fabrication of catalytic systems based on hetero-and homometal-chalcogenide clusters of Pt-M-X type (M: Fe, Mn; X: S, Se, Te), which provides the reproducibility of catalyst composition and uniform distribution of catalyst over the carbon support, is proposed. Thus obtained catalysts are characterized using the XRD, TEM, and EDAX methods. The electrocatalytic activity of these systems in the oxygen reduction reaction, the role of the nature of chalcogenide atom and the atom of the second metal, which is the platinum partner, and the electrochemical behavior of nonplatinum chalcogenide systems are studied.     

The kinetics of phase transitions in vitreous chalcogenide semiconductors As10.2Se89.8 and As9Se90Bi in early stage of physical ageing process

The kinetics of glass transition in selenide glasses As_10.2Se_89.8 and As₉Se₉₀Bi in early stage of physical ageing process has been investigated by parallel differential scanning calorimetry (DSC) and exoelectron emission (EEE). It has been found that the glass transition process occurring in investigated glasses is evidenced by peaks on EEE intensity and DSC curves. Admixture of bismuth causes a distinct lowering of the temperature of glass transitions process both in the surface layer and in the volume. The addition of Bi causes a decrease in the value of the activation energy for glass transition process in both the volume and in the surface layer, thus reducing the thermal stability of investigated glasses. Physical ageing in Se-rich chalcogenide glasses leads to a significant increase of endothermic peak area A, temperature of glass transition T _g and decrease of the activation energy value E. All these effects are strongly dependent on glass composition.     

New Forms and Functions of Tellurium: From Polycations to Metal Halide Tellurides

Metal chalcogenides and metal chalcogenide halides are distinguished by their structural diversity and by their very different physical properties. Therefore, the synthesis of novel compounds from this class is always a rewarding goal for the preparatively oriented solid-state chemist. Over the past few years, many syntheses and structural investigations have stimulated the field. The emphasis of the research has been placed on selenium-rich and tellurium-rich compounds, which are characterized by directed covalent bonds between the chalcogen atoms. Compounds with novel chalcogen polycations have also become accessible during the past few years by reacting the chalcogen elements with transition metal halides, or from chemical vapor deposition in the sense of chemical transport reactions. In these compounds, tellurium differs from its lighter homologues by a pronounced tendency towards greater covalence. This article attmepts to provide an overview of new developments in the field of compounds with chalcogen polycations and of metal chalcogenide halides, with an emphasis on compounds containing molybdenum and tungsten as the transition metals and tellurium as the chalcogen.     

Tetranuclear rhenium chalcogenide cluster complexes with a cubane core. Synthesis,structures, and properties

The results of studies of rhenium chalcogenide cluster complexes with the [Re₄Q₄] cubane core, where Q = S, Se, or Te, are reviewed. Different approaches to the synthesis of these compounds are surveyed and their properties and structures are considered. Substitution reactions in the cluster core and replacements of terminal ligands are discussed. The formation of polymers consisting of the tetranuclear rhenium chalcogenide cyanide clusters as structural building blocks is considered.     

Structure–property relationships in multicomponent oxide glasses

Cations play a complex structural role in oxide glasses, as they occur in different kinds of environments, which allow them to exert a contrasted influence on physical and chemical properties of these glasses. The combination of structural information given by a wide range of spectroscopic methods and by radiation scattering, combined with numerical modelling, has given insight on the structural organisation around these cations. Among these characteristic properties are unusually low-coordination numbers, such as 5-fold coordination, and the presence of extended ordered domains, in which cation polyhedra are edge- or corner-sharing. This review presents evidence for a structural control of several physical and chemical properties in oxide multicomponent glasses. The use of zinc as a stabilising glass component arises from its network-forming position, which implies the presence of low-charge cations in its surrounding and as a consequence decreases the concentration of modifier components. The compositional dependence of glass coloration by transition elements has been investigated thoroughly through the example of nickel in silicate and borate glasses. The wide range of coloration observed may be explained by the existence of three kinds of environments, with nickel occurring in 4-, 5-, and 6- coordination. The relationships of these sites with the medium-range organisation of the glasses have been understood by a combined use of EXAFS spectroscopy and neutron scattering with isotopic substitution. The two other examples that are presented to illustrate structure–property relationships concern the physical solubility of gazes in glasses and the alteration processes of glasses used as analogues of nuclear waste matrices. In this last example, the use of structural probes as zirconium illustrates the influence of the alteration solution on the process of glass corrosion and further development of a gel at the glass–solution interface. A comparison with the evolution of the surrounding of iron shows that the two major processes, hydrolysis/condensation and dissolution/precipitation, depend on the element considered.     

Structural change in Li and Na aluminophosphate glasses: evidence of a "structural mixed alkali effect"

The short- and long-range structure of a series of single and mixed aluminophosphate glasses with the general composition [xNa(2)O (46 - x)Li(2)O], [yAl(2)O(3) (54 - y)P(2)O(5)] is analyzed using (31)P and (27)Al magic-angle spinning (MAS) NMR as well as small-angle X-ray scattering. These series of glasses allow analyzing both the effect of alumina incorporation in these glasses, for small alumina content (y = 0, 4, 8), and the structural changes associated with the so-called mixed alkali effect (x = 0, 11.5, 23, 34.5, 46). Our results indicate that aluminum is mainly octahedrally coordinated in these glasses and that there is most likely some segregation of the Al(OP)(6) species. In the pure phosphate glasses, we observe a "classical" continuous variation of the structural properties with the relative alkali content, but in the aluminophosphate, both local and long-range structural results reveal for the first time some nonlinear change as a function of the relative alkali content.