共查询到20条相似文献,搜索用时 46 毫秒
1.
119Sn Mössbauer measurements have been carried out on 18 chalcogenide glasses of different composition in the system SeSnAs. In all cases tin is four-coordinated and appears to be tetrahedrally surrounded by selenium. Two of the glasses (Se60Sn3As37 and Se47Sn3As50) were crystallized by heat treatment, and their Mössbauer spectra have been measured as a function of crystallization temperature and annealing time. As a result of the heat treatment, crystalline SnSe and SnSe2 are precipitated. The amount of each compound is determined by the composition of the original glass and the remaining glassy or crystalline phase (As2Se3 and As4Se4). The degree of the crystallization depends on the temperature and the annealing time, but not the mass ratio of the tin selenides formed. 相似文献
2.
《Journal of Non》2007,353(13-15):1337-1340
The preparation of mixed glasses of As2S3−xSex (x = 0–3) and (1 − y) · As2S3y · Sb2S3 (y = 0–1) has been carried out by an in situ pouring technique. X-ray diffraction (XRD) was used to confirm the glassy nature of the materials and monitor devitrification. Visible-IR transmission, photoluminescence, refractive index and micro-Raman were measured as a function of composition. Microhardness (MH) and thermal expansion coefficient (TEC) were also measured. Raman peaks in As2S3 and As2Se3 were observed around 338 cm−1 and 230 cm−1, respectively in this first composition series in which S was replaced by Se. When As was replaced by Sb, in the case of second composition series, the As2S3 related Raman peak became broader and shifted to lower wave number, reflecting some structural change/devitrification. MH increased (1.31–1.50 GPa) with Se and Sb content while the TEC was found to decrease (2.5–1.4 × 10−5/K). The progressive increase in the content of either Se or Sb in As2S3 is anticipated to modify bond lengths and bond angles. The combined effect of these structural modifications would change the local structure of the glass forming a more rigid glass network thereby increasing the hardness and decreasing TEC. 相似文献
3.
The aim of this work is to investigate and qualify vitreous regions in new chalcogenide systems containing highly polarizable elements like S, Se, As, Sb, Bi, Pb and I. The sulfur based system, As2S3-Sb2S3-Bi2S3-PbI2, as well as the selenium containing glasses As2Se3-Sb2Se3-PbI2 have been studied. Large vitreous regions have been defined in the both systems: sulfur and selenium. Indeed, several glass compositions can accept in the vitreous network a molar concentration near 50% of PbI2. Physical properties such as glass transition temperature, crystallization temperature, optical transmission, band-gap wavelength have been measured versus glassy compositions. 相似文献
4.
《Journal of Non》2007,353(13-15):1441-1445
This paper deals with sensitivity of chalcogenide based photoresists in inorganic alkaline solutions. The thin films of As33S67, As33S50Se17, As33S33.5Se33.5, As33S17Se50, and As33Se67 were studied. The selective wet-etching was carried out using NaOH, Na2S and (NH4)2S alkaline solutions. The different sensitivity according to sample composition and used etching solution were found. Chalcogenide films as a potential photoresists could be classified either as ‘high-contrast’ or ‘low-contrast’ depending on the sample compositions, type of etchant and its concentration or on incident light energy. 相似文献
5.
The structure of the semiconducting glassy As2Se3Hgx system was investigated in a composition range x = 0.005?0.12. An explanation of the anomalous behaviour of the macroscopic density is proposed, based on the analysis of radial electron density distribution curves. A formula is given which correlates quantitatively the magnitude of coordination spheres with the experimental macroscopic density. 相似文献
6.
Toshiaki Ohsaka 《Journal of Non》1976,22(2):359-366
The infrared (IR) absorption spectra for YxZxSxSe100?3x glasses (Y = Ge, As; Z = As, te), with x = 2.5 and 5.0, are measured in the wavenumber region 700-60 cm?1 at room temperature. These IR spectra are qualitatively explained by comparing with the IR spectra of the binary and ternary glasses. In GexAsxSxSe100?3x glasses (x ? 5.0), the main spectral features are explained by both spectra of the two ternary glasses GexSxSe100?2x and AsxSxSe100?2x. In GexSxTexSe100?3x glasses (x ? 5.0), the main spectral features are well explained by both spectra of the two ternary glasses GexSxSe100?2x and GexTexSe100?2x. On the other hand, main spectral features in AsxSxTexSe100?3x glasses (x ? 5.0) are well explained by both spectra of the ternary glasses AsxSxSe100?2x and the binary glasses Se100?xTex. In these glasses with low concentrations (x ? 5.0) some chemical bonds are confirmed and some structural units estimated. 相似文献
7.
Data are presented on the dc conductivity, thermopower and optical absorption of glasses in the CuAs2Se3 system. The electronic properties of the alloys differ markedly from those of As2Se3, but variations in composition do not introduce significant changes in properties, until the atomic percent of copper is greater than 25. The results are interpreted in terms of small polaron transport. 相似文献
8.
75As Nuclear Quadrupole Resonance (NQR) lineshape measurements for the amorphous mixed chalcogenide system As2SxSe3?x are reported. The line-shapes are asymmetric and approximately 8 MHz in width (full width at half maximum). The peak resonance frequency is observed to increase approximately linearly with x. The NQR results indicate the presence of mixed As2(S, Se)3 pyramidal structural units and are thus not consistent with models that predict the occurrence of anion subsite segregation. NQR measurements performed on crystalline As2SSe2 lend support to the structural model proposed for the glasses. 相似文献
9.
A study of infrared absorption in the 250–4000 cm?1 region has been carried out for 0.5 As2Se30.5 GeSe2 glasses quantitatively doped with oxide impurity. The frequencies of the intrinsic 2- and 3-phonon absorption bands at 490 and 690 cm?1 correspond well to those predicted from combinations of the high frequency bands in the first order IR and Raman spectra of As2Se3 and GeSe2 glasses.Glasses doped with As2O3 exhibit the same oxide impurity absorptionbands as those doped with GeO2. Unlike As2Se3 glass, at impurity concentrations up to 1000 ppm As2O3, 0.5 As2Se30.5 GeSe2 glass exhibits only one major oxide impurity species, characterized by absorption bands at 780 and 1260 cm?1 and due to oxygen bonded to network Ge. The observation of a much weaker network AsO vibration band at 670 cm?1 confirms that oxygen bonds preferentially to Ge in this glass. The same minor oxide species appears to determine excess IR absorption at the CO2 laser wavelength of 10.6 μm in both As2Se3 and 0.5 As2Se3 0.5 GeSe2 glasses. The frequencies and intensities of absorption bands due to hydrogen impurities are also quite comparable for these two materials. 相似文献
10.
J.S. Sanghera C.M. Florea L.B. Shaw P. Pureza V.Q. Nguyen M. Bashkansky Z. Dutton I.D. Aggarwal 《Journal of Non》2008,354(2-9):462-467
High purity chalcogenide glasses were prepared in the series As2S(3?x)Sex where x = 0 to 3. The measured third order non-linearities increase with the value of x, and are up to about 1000 times larger than silica for As2Se3 glass. We show that the anharmonic oscillator model, using the normalized photon energy, gives an excellent fit to the data over three orders of magnitude. Single mode optical fibers based on As2S3 and As2Se3 glasses have been fabricated using the double crucible technique and the Stimulated Brillouin Scattering (SBS) investigated. The threshold intensity for the SBS process was measured and used to estimate the Brillouin gain coefficient. Preliminary results indicate record high values for the figure of merit and theoretical gain, compared to silica, which bodes well for slow-light based applications in chalcogenide fibers. 相似文献
11.
The local order in amorphous films of As2Se3, As2Se2Te, As2SeTe2, and As2Te3 has been examined by scanning electron diffraction with direct recording of the intensity of the elastically scattered electrons. The radial distribution functions indicate that there is a systematic increase in mean nearest neighbor distance as the Te concentration is increased, butthe mean coordination number increases slightly around 2.4. Pair function calculation of models shows that the 3-aand 2-fold coordinations of arsenic and chalcogens are retained in these glasses and the interatomic distances are close to those predicted from the Pauling covalent atomic radii of the constituent atomic species. The short range order appears to be similar in amorphous and crystalline As2Se3, but different in the case of As2Te3 as found by previous workers on bulk materials. 相似文献
12.
Correlation between the real part of the dielectric constant and the structure of glasses in the system AsxSe1?x and GexSe1?x is reported. The mole polarization is calculated using the Sellmeyer approximation neglecting the Lorentz field. The vibrationally caused part of the permittivity which is obtained by subtraction of the mole refraction reflects ordered states in the investigated series. Besides the known crystalline compounds As2Se3 and As4Se4 the formation of the vitreous AsSe3 and As3Se2 from the liquid state has to be supposed. In the system GexSe1?x the formation of the compounds GeSe2 and Ge2Se3 is completed by GeSe4 which as Ge2Se3 obviously only exists in the non-crystalline state. GeTe4 has been reported as a metastable crystalline phase. The temperature dependence of ?r of vitreous As2Se3 is tentatively interpreted in terms of the dipole orientation caused by conversion of the charge in valence alternation pairs. 相似文献
13.
Adrian C. Wright Bruce G. Aitken Richard Haworth J. Ross Stewart 《Journal of Non》2011,357(14):2502-2510
A neutron diffraction investigation has been performed of the structure of four chalcogenide glasses, using the D4c diffractometer on the high-flux reactor at the Institut Laue-Langevin (ILL). Vitreous Ge3As52S45 is shown to have a structure based on As4S3 molecules, whereas that of its selenide analogue, vitreous Ge3As52Se45, involves far fewer As4Se3 molecules. Two As2X3 reference glasses (X = S or Se) have purely network structures. As-X, and As-As bond lengths have been extracted, together with their associated co-ordination numbers, from peak fits to the real space correlation functions, T(r), and suggest that all four glasses are chemically ordered; i.e. that they contain the maximum possible number of As-X (and Ge-X) bonds. The molecular nature of vitreous Ge3As52S45 is evident from the enhanced first diffraction peak relative to the As2S3 reference glass, and has been further investigated by comparing its interference function, Qi(Q), with that expected for an isolated As4S3 molecule. On the other hand, the second diffraction peak for vitreous Ge3As52S45 is not reproduced by a random orientation molecular model, indicating that there is orientational correlation between adjacent molecules, and this is discussed with respect to the structure of the corresponding As4S3 crystalline phases. The neutron-weighted vibrational density of states (VDOS) for vitreous Ge3As52S45, obtained with the ISIS MARI spectrometer, unambiguously confirms the existence of As4S3 molecules, as revealed by a peak at ~ 34 meV arising from the triangle of As atoms that form the base of the molecule. MARI data recorded at ambient temperature also reveal a strong quasi-elastic component in the scattered intensity, which has been further investigated using the IN5 quasi-elastic scattering spectrometer (ILL) and indicates the presence of rotational diffusion of the As4S3 molecules; i.e. that, at ambient temperature, vitreous Ge3As52S45 behaves as a plastic glass. A possible structural model for vitreous Ge3As52S45 comprises a two-dimensional tangled GeS2 net with As4S3 molecules trapped in its folds whereas, for vitreous Ge3As52Se45, a clathrate model appears more appropriate. 相似文献
14.
K.S. Liang 《Journal of Non》1975,18(2):197-207
The local atomic arrangement in amorphous As2Se3As4Se4 glasses was investigated with ESCA (electron spectroscopy for chemical analysis) and RDF (radial-distribution function) analysis. Measured changes of RDF peak areas and ESCA chemical shifts give direct evidence for the preservation of the local bonding schemes of both crystalline As2Se3 and As4Se4 in their amorphous states. The valence-band structures of amorphous As, Se, As2Se3 and As4Se4 are also measured with ESCA and discussed in conjunction with the bonding schemes of these glasses. 相似文献
15.
dc conductivity and Seebeck measurements have been carried out at temperatures below Tg on well characterized bulk samples of amorphous As2Te3, As2Se3, and As2S3. Several models for conduction in these materials have been compared to the data. It is concluded that the models involving polaron hopping conduction are in better agreement with available data than are models involving hopping in the tails of localized band-tail states. 相似文献
16.
Ramakanta Naik K.V. Adarsh R. Ganesan K.S. Sangunni S. Kokenyesi Uday Deshpande T. Shripathi 《Journal of Non》2009,355(37-42):1836-1839
Photoinduced diffusion in Se/As2S3 and Sb/As2S3 nanomultilayered thin films are studied by X-ray photoelectron spectroscopy (XPS). The XPS measurements show the atomic movements during photoinduced diffusion in Se/As2S3 and Sb/As2S3 nanomultilayered film. The analysis of experimental data describes the nature of light induced changes in different structural units. 相似文献
17.
《Journal of Non》2006,352(23-25):2430-2433
In this study, we report the first measurements of wavelength and pulse length dependence of ablation thresholds in glassy As2Se3. Ablation yields, obtained from time-of-flight spectra were compared to laser intensity curves to obtain laser ablation thresholds. The wavelength dependence of the ablation thresholds were obtained by tuning the Vanderbilt–Keck free electron laser in the range of 3.2–5 μm. Pulse dependence of the ablation thresholds were obtained with a 5 μs macropulse in the wavelength range 3.2–5 μm and with macropulses ranging from 200 to 1000 ns at the wavelength of 3.5 μm. The wavelength dependence of the ablation threshold did not indicate that impurity absorption was a major factor in the ablation process in glassy As2Se3. The ablation threshold decreased with wavelengths corresponding to higher photon energies. In addition, a sharp increase in ablation threshold was observed with decrease in the macropulse length. Optical images of ablation craters at intensities above the threshold reveal significant melting on the sample surface. We will discuss the wavelength and pulse length dependence of the laser ablation threshold in glassy As2Se3 in terms of a multi-photon process and a cumulative heating process. 相似文献
18.
Amorphous thin films from the system As2Se3-Ag4SSe-SnTe were prepared by thermal vacuum evaporation from the corresponding bulk glassy samples. The film structure and surface morphology were investigated by scanning electron microscopy and atomic force microscopy; the results revealed uniform, smooth and homogeneous coatings. The amorphous chalcogenide films are transparent in a wide spectral range as shown by transmission and reflection measurements in the VIS and NIR regions. The optical band gap was determined and its compositional dependence is discussed in terms of structural considerations and the formation of charged defect centers. 相似文献
19.
Thin films of composition AsSeχ where 0.8 ≤ χ ≤ 1.0 obtained by the evaporation of both crystalline and glassy As2Se3 have been examined for their high-field behaviour. The films exhibit two essentially linear I–V regions with a smooth nonlinear change over. While the initial linear region may perhaps correspond to a Poole-Frenkel emission, the very high-field linear region is likely to arise from a distortion of the band shapes and lowering of the mobility gap. 相似文献
20.
Velocities of 30 MHz longitudinal and shear ultrasonic waves have been measured in As2S3 and As2Se3 glasses as a function of hydrostatic pressure up to 1.5 kbar at 195 K and 3 kbar at 296 K. The elastic stiffness moduli are found to have relatively large, positive, pressure dependences which are about the same at both temperatures for both glasses. This behavior is attributed to the weakness of bonding between layers comprised of AsS3 and AsS3 pyramids.Inspection of data for a variety of glasses reveals a correlation between the value of CL/3CT and whether the elastic moduli are increased or decreased by pressure. (CL is the longitudinal modulus and CT the shear modulus.)Using the pressure dependences of the elastic moduli obtained in the present work, it is found that volume change is responsible for most of the temperature dependences of the moduli. In addition elastic gammas are obtained which are consistent with thermal Grüneisen gammas at 12 K. The pressure dependence of the volume of As2S3 glass at 296 K is calculated using the present results in the Murnagham equation. Agreement with volumetric data of Weir is obtained. 相似文献