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1.
Se, As and Ge self-diffusion were investigated in three different glasses of the chalcogenide system SeGeAs by means of the radioactive tracers 75Se, 73As and 71Ge. All D values (Se between 200 and 290°C, As between 240 and 290°C and Ge between 280 and 295°C) lay between 10?14 and 5 × 10?16 cm2 s?1. The diffusion profiles were analyzed using a chemical micro-etching technique. Roles of glass structure and possible diffusion mechanism are discussed. 相似文献
2.
Koichi Shimakawa 《Journal of Non》1981,43(2):229-244
It is found that the optical gap EAB for amorphous A-B alloys can be determined by the energy gap EA for element A and EAB for the element B in the equation EAB(Y) = YEA + (1?Y) EB where Y is the volume fraction of element A. Calculations based on a random bond network agree with experiments for SiGe, SbSe, and AsTe films (class A). Calculations based on a chemically ordered bond network which tends to form microscopic molecular species gree with experimental results for the AsSe, AsS, GeTe and Sb2Se3As2Se3 systems (class B). In contrast to the above systems, agreement with experiment is not obtained for the TeSe, As2Te3As2Se3 and GeTe2GeSe2 systems which contain atoms of both Te and Se (class C). The classification into three types (classes A, B and C) is consistent with the calculation based on effective medium percolation theory which interprets the compositional dependence of the conductivity of chalcogenide glasses. 相似文献
3.
The introduction of Ag in SiAsTe glasses permits the incorporation of Se, otherwise volatile and/or degradable as a constituent in Si-containing chalcogenide glasses. SiAsAgTeSe glasses exhibit much higher softening ranges and glass transition temperatures than encountered in known chalgogenide systems. A glass Si35As15Ag10Te20Se20 had the viscosity log ν = 13 at about 500°C, as compared to 370°C for the base glass Si35As25Te40, the viscosity of log ν = 9.8 at about 560°C, as compared to 442°C for the base glass. Phase separation occurs in the system SiAsAgTeSe and becomes manifest in two glass transitions indicated by changes in the slopes of the expansion curves and breaks in the softening point-composition relations. The existence and behavior SiAsAgTeSe glasses suggests the possible development of higher Tg i.r. transparencies and higher Tg semiconductor glasses than described so far. 相似文献
4.
When CuAsSe glasses are irradiated, they exhibit higher concentrations of darkening than AsSe glasses. Since darkening depends on the composition, the darkening centers in CuAsSe glasses to be of the same kind as those in AsSe glasses, i.e. arsenic clusters. Concerning the kinetics of erasing, it was found that the activation energy and the rate constant of erasing in CuAsSe are almost equal to those in AsSe glasses, but for the kinetics of darkening, it was found that the activation energy of darkening is equal to that of AsSe but α0, which is proportional to the number of latent darkening centers, and the darkening rate constant k1 are about twice as high as the corresponding constants of AsSe glasses. This may be the reason for the greater darkening in CuAsSe glasses. The high value of α0 was attributed to the generation of more AsAs bonds on the addition of Cu to the AsSe glass network. The high value of k1 was attributed to the increase in efficiency of photo-decomposition because of the many impurity levels in the band gap and also because of the narrow optical energy gap in the CuAsSe glasses. 相似文献
5.
The glass transition temperatures were measured in the systems AsS, As0.5P0.5S, PSe, AsSe and PAsSe. Heat capacities of the glasses in the selenium systems were obtained by differential scanning calorimetry. As shown by the residual entropies departures from ideality are high in the chalcogen glasses. The results are discussed in terms of the structure of glasses in these systems. The thermodynamic data of glasses and liquids in these systems indicate a balance of intra- and intermolecular saturation of bonds. The amount of polymerization increases with increasing average molecular weight in the glass and with increasing temperature in some of the investigated liquids. 相似文献
6.
《Journal of Non》1986,83(3):272-281
The optical properties near the fundamental absorption edge has been studied for a series of SixSe1−x glasses using photoacoustic spectroscopy. The compositional dependence of the bandgap EO, derived from these measurements, is presented and contrasted with the GeSe and the SiS systems. This data is qualitatively explained with a model which accounts for differing numbers of homopolar and heteropolar and heteropolar bonds as the composition is varied. Additional support for this interpretation is found in the compositional behavior of the glass transitions of these alloys. 相似文献
7.
Fang Xia S. Baccaro Wei Wang L. Pilloni Xianghua Zhang Huidan Zeng Guorong Chen 《Journal of Non》2008,354(12-13):1137-1141
Nanophase separation in the bulk Ge–As–Se chalcogenide glasses was observed by SEM and supported by XRD and IR measurements. Effects of nanophase separation on glass transition temperature (Tg), microhardness (Hv), optical band gap (Eopt) and thermal expansion coefficient (α) were investigated in terms of glass rigidity transitions. According to the correlations between the properties and average coordination number Z, it is established that nanophase separation becomes more intensive when Z is larger than 2.64. 相似文献
8.
The paper reports dielectric measurements carried out for a variety of threshold and memory alloys of glassy AsGeTe and SeGeTe at different temperatures (83 to 373 K) and various frequencies (0.2, 0.5, 1.0, 2.6 and 5.0 MHz). It is found that the glassy system of chalcogenides exists in the form of molecular dipoles which remain frozen at low temperatures and, as the temperature is increased, the molecules attain freedom of rotation at temperatures which are sometimes as low as 253 K. All the materials displayed dielectric dispersion in the radio frequency range. Gevers' formula has been used to calculate the dielectric loss (?′') and loss-angle (tan δ) from the measured values of the real part of dielectric constant (?′). The curves: log ?′ versus temperature, ?′ versus log ω, ?″ versus log ω, tan δ versus log ω and tan δ versus temperature, gave a direct evidence of the existence of a Debye-type relaxation having a wide distribution of relaxation times.Cole-Cole diagrams have been used to determine the distribution parameter (α) and the molecular relaxation time (τ). The temperature dependence of α and τ for all the alloys is consistent with the “molecular relaxation mechanism”. The paper also reports accurate values of the static and optical dielectric constants for all the alloys.Eyring's relaxation rate equations have been used to determine the free energy of activation (ΔF), and enthalpy of activation (ΔH) for all the alloys. These results indicate the existence of a stronger intermolecular interaction for SeGeTe alloys. mott's concept of “dangling bonds” has also been used to explain the existence of a stronger intermolecular interaction, and hence a greater density of defect states in case of SeGeTe as compared with AsGeTe alloys.It has been finally concluded that the dielectric behaviour of chalcogenide glasses, in general, can be successfully explained by using the theory of molecular relaxation. 相似文献
9.
Electrical conduction in various inorganic glasses was studied as a function of hydrostatic pressure up to 2000 atm and phenomenologically classified into electronic, ionic and mixed types. In electronically conducting glasses such as AsSe chalcogenide glasses and Fe2O3P2O5 glass, the conduction is enhanced by application of pressure. On the other hand in ionically conducting glass such as Na2OB2O3 glass, the conduction is suppressed through the concept of an activation volume. The compatibility of electronic and ionic conduction processes in glasses such as Ag-doped AsSe glasses and Bi2O3B2O3 glass, which have more complex conduction processes, was discussed from these aspects. 相似文献
10.
Flocculent inhomogeneities in vitreous Ge2Se3 were identified as being SiO2. The origin of these particles was found in the walls of the vitreous silica tubes in which the glass was prepared. By etching or thermal treatment of the tubes prior to their use the concentration of the microheterogeneities in the selenide glass can be considerably reduced. This is also valid for the preparation of glasses of the system GeAsSe and GeSbSe. 相似文献
11.
Guoping Dong Haizheng Tao Saisai Chu Xiudi Xiao Shufeng Wang Xiujian Zhao Qihuang Gong 《Journal of Non》2008,354(2-9):440-444
Ultrafast third-order optical nonlinearity of Ge–Ga–Ag–S chalcogenide glasses at the wavelength of 820 nm has been measured using femtosecond time-resolved optical Kerr (OKE) technique. The results show that Ge–Ga–Ag–S glasses have large third-order optical nonlinear susceptibility, χ(3) and the response time is also subpicosecond, which are predominantly due to the ultrafast distortion of electron cloud surrounding the balanced positions of Ge, Ga, Ag and S atoms. What’s more, a strong dependence of χ(3) on the composition and microstructure of these glasses was found which shows that [GeS4] and [GaS4] tetrahedra play an important role on the third-order optical nonlinearity. These Ge–Ga–Ag–S chalcogenide glasses would be expected as promising materials applied on all-optical switching devices. 相似文献
12.
In order to better understand the distribution of tetrahedra in multicomponent tetrahedral network structures of melts and glasses, we have investigated the Raman spectra of binary SiO2GeO2 glasses. We compare the Raman spectral features of the end-member glasses and discuss their vibrational origins. The mixing of GeO2 and SiO2 melts results in a continuous random network structure of TO4 tetrahedra (T Si, Ge) in the glass. Raman bands corresponding to the asymmetric stretch (vas) of oxygen in GeOGe, SiOSi and SiOGe bonds are observed in the glasses having intermediate compositions along the SiO2GeO2 join. The presence of three distinct vas (TOT) bands in the spectrum of a glass having Si/Ge one reveals that a considerable degree of SiGe disorder exists in the glass. The presence of a single symmetric oxygen stretching band in the spectra of binary SiO2GeO2 glasses indicates that the symmetric stretch modes (vs) of oxygen in SiOSi, SiOGe and GeOGe bonds are strongly coupled. An observed decrease in the halfwidth of the vs (TOT) band in the spectra of SiO2GeO2 glasses with increasing concentration of GeO2 may be attributed to a decrease in the average TOT bond angle and a predominance of six-membered ring structures. Results of the present study support the assignment of the bands in the 900–1200 cm?1 region of the alumino-silicate glasses, spectra to the vas(AlOSi) and vas(SiOSi) modes. In contrast to the alumino-silicate glasses, however, the SiO2GeO2 glasses have a much higher degree of disorder of the network-forming cations. 相似文献
13.
New compouning techniques were devised to prepare high-purity Ge28Sb12Se60 (TI 1173)and Ge33As12Se55 TI 20). The methods were based on the combination of the reactant purification and compounding steps. The goal of the program was to establish the absorption limit for the glasses and to lower the absorption at 10.6 μm. At the present purity level, the GeSbSe glass is found to have an absorption level of about 0.01 cm?1 at 10.6 μm while the absorption level for the GeAsSe glass is 0.05 cm?1. Underlying causes for the limits are discussed along with the possibilities for improvement. 相似文献
14.
We have used differential scanning calorimetry (DSC) to examine the thermally induced transformations of bulk and thin-film amorphous alloys within a large portion of the GeSeTe system. Most chalcogen-rich compositions showed a discontinuous increase of heat capacity when heated through the glass transition temperature TG. The Ge-rich compositions, which could only be prepared as sputtered amorphous films, were invariably characterized by an irreversible exothermic crystallization process on heating, beginning at the crystallization temperature TX. Values of Tg and TX have been tabulated for all alloys investigated and the compositional dependence of Tg has been examined in the light of recent models for viscous flow in glass-forming chalcogenide systems. In addition, a region of liquid immiscibility has been observed in the vicinity of Ge20Se40Te40 in which a GeSe2-rich liquid phase segregates from a tellurium-rich liquid phase. The existence and limits of this immiscibility region have been rationalized on the basis of ionic perturbations to the covalent bonding. The segregation of a GeSe2-rich liquid increases the concentration of GeSe bonds which are the strongest and most ionic of the six angle-bond types which can occur in this system. 相似文献
15.
X-ray diffraction studies of glasses in the following ternary systems have been made: Na2OMgOSiO2, Na2OZnOSiO2, Na2OCaOSiO2 and Na2OBaOSiO2. The following heavy atom substitutions have been used: Ag for Na and Ge for Si. The changes in the electron radial distribution curves resulting from AgNa replacement can be explained as amplifications of relatively well-defined NaSi distances, which are nearly the same in all the glasses investigated. The GeSi substitution causes changes which can be explained on the basis of isostructural GeSi substitutions. 相似文献
16.
The results of the measurement of transverse and longitudinal sound velocities on eigth glass compositions of the GeSbSe system are reported and their elastic moduli evaluated. While the velocities, elastic moduli and Debye temperature show variation with composition for GexSb10Se90?x glasses, they are essentially constant for the glasses with stoichiometric compositions. The dependence of bulk modulus on mean atomic volume has been analysed. Both the mean atomic volume and the type of bonding are found to be effective in determining the composition dependence of bulk modulus. 相似文献
17.
《Journal of Non》2007,353(13-15):1291-1297
Elastic/plastic properties of Ge–Se binary and Ge–Sb–Se ternary chalcogenide glasses were explored by indenting with Vickers and Brinell (spherical) microindenters using static and ‘instrumented’ (load versus penetration) recording machines and analyzed further using a non-contact profilometer. The load-dependence of microhardness, indentation fracture toughness and brittleness versus the average covalent coordination number, 〈r〉, were studied. It is concluded that the elastic recovery of deformations is maximized at ∼GeSe4 (〈r〉 = 2.4), which is consistent with ‘optimized connectivity’ of the rigidity percolation arguments. Surprisingly, many of the extrema were nearly non-existent in the ternary glasses. 相似文献
18.
The evolution of the structure of SbxGe40-xSe60 (x = 8, 12, 15, 18 and 20) chalcogenide glasses is determined by high resolution X-ray photoelectron spectroscopy as Sb is added and the average coordination number (Z) is varied from 2.60 to 2.72. For glasses with Z < 2.67 the structure consists of deformed tetrahedra and pyramids, in which at least one Se atom is substituted by Ge or Sb atoms. Increase in the concentration of cations beyond Z ≥ 2.67 leads to a strengthening of the above regularity and formation of the structure by shared pyramids and tetrahedra with two or more Se atoms substituted by cations. At the same time Se–Se dimers are present in all the investigated compositions while they are not expected in these Se-deficient glasses. Their formation dictates that there must be metal-rich regions somewhere in the structure. 相似文献
19.
《Journal of Non》1986,79(3):285-294
The structure of Na2OGeO2 melts in the temperature range from 1100 to 1150°C has been investigated with the high temperature X-ray diffraction technique. Comparing the radial distribution functions obtained for the melts with those for the corresponding glasses, the first peak due to the GeO interatomic distance is invariant upon melting, although it becomes broader due to thermal vibration. The second peak for the GeGe interatomic distance for melts shifts toward the large distance, which is explained by broadening of the GeOGe bond angle, not by the thermal expansion of the GeOGe bond. The composition dependences of GeO distances and coordination numbers of the Ge4+ ion of the melts are found to be almost the same as the corresponding glasses, indicating that even in melts at such high temperatures 6-fold coordinated Ge4+ ions are present and their content changes with the Na2O content as in the case of the corresponding glasses. 相似文献
20.
Resistivity and thermoelectric power were measured as a function of temperature and composition for Ge20BixSe70?xTe10 glasses (x = 0–11). The results were compared with the case of of Ge20BixSe80?x glasses to see on the electrical properties the influence of the substitution of Te for a part of Se. The glasses show n-type conduction for x ? 9, which was not affected by the substitution of Te. The resistivity was about three orders of magnitude lower for the glasses with x < 10, and remained almost the same for x ? 10, compared with the glasses not containing Te. From the composition dependence of the calculated concentration of covalent bonds in the glasses, it was proposed that the appearance of n-type conduction was closely related to the formation of a sufficient number of BiSe bonds and the disappearance of the bonds between two chalcogen atoms such as TeSe or SeSe bonds, and that the remarkably low resistivity in the present glasses with x < 10 was likely to be attributed to the formation of TeSe bonds. 相似文献