Effect of Oxygen Impurity on the Optical Transmission of As2Se3.4Glass

As₂Se_3.4glass samples with controlled oxygen content in the range (1.4–7.9) × 10^–2wt % were used to assess the effect of oxygen impurity on the IR absorption spectrum of the glass. The spectral dependence of the extinction coefficient for oxygen impurity was determined in the range 600–1400 cm^–1. It was shown that the presence of 10^–5wt % O gives rise to additional losses comparable to the intrinsic losses in the CO₂lasing range.     

Infrared spectra and composition dependence investigations of the vitreous V2O5/P2O5 system

A series of glasses in the V₂O₅-P₂O₅ system was prepared and their compositions analysed. The glass densities and molar volumes were determined. The results obtained revealed three compositional regions. In addition, the infrared absorption spectra of these glasses were measured at room temperature in the frequency range 1600–200 cm^–1. The compositional dependence of the bands present, attributed to a given band and mode of vibration, was investigated. However, the infrared data confirmed the results obtained from the density and molar volume measurements.     

Effects of oxygen and carbon impurities on the optical transmission of As<Subscript>2</Subscript>Se<Subscript>3</Subscript> glass

The IR spectra of As₂Se₃ glass samples containing known amounts of oxygen (4 × 10^-3 to 7.7 × 10^-2 wt %) or carbon (5.8 × 10^-3 wt %) are measured, and the parameters of impurity-related absorption bands and extinction coefficients are determined. The effects of oxygen, carbon, sulfur, and hydrogen on the transmission of As₂Se₃ glass are analyzed. At an oxygen content on the order of 10^-5 wt %, this impurity causes optical losses in the range 900–1100 cm^-1 comparable to the intrinsic losses. The permissible carbon content of As₂Se₃ glass is 10^-6 to 10^-5 wt %. Carbon inclusions 0.07 µm in diameter cause optical losses comparable to the intrinsic losses in the spectral window of As₂Se₃ glass when present in a concentration of 10⁴ cm^-3.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 369–376.Original Russian Text Copyright © 2005 by Shiryaev, Smetanin, Ovchinnikov, Churbanov, Kryukova, Plotnichenko.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Optical absorption spectra studies for amorphous Cu2O-Bi2O3 glass system

Infrared absorption spectra were measured in the spectral range 4000–200 cm^–1 for the Cu₂O-Bi₂O₃ glass system. Strong bands were observed around 436–477, 600–632, 700–715, 810–875, 975–1000, 1550–1610 and 3225–3510 cm^–1 which are due to harmonics of the Bi-O-Bi stretching vibration, Cu-O stretching vibrations, O-Bi-O stretching vibrations, O-Bi-O bending vibrations, Bi-O stretching vibrations, free H₂O normal-mode bending vibrations and free H₂O molecules or OH^– ions, respectively. Quantitative justification of these absorption bands shows that the values of the experimental wave number for most recorded absorption bands agree well with the theoretical ones.The optical absorption spectra were recorded for the same glass system in the spectral range 300–700 Nm. These records show that the absorption edge has a tail extending towards lower energies. The edge shifts towards lower energies with increasing Cu₂O content. This shift is mostly related to the structural rearrangement and the relative concentrations of the glass basic units. By increasing the Cu₂O content, the optical energy gap decreases, while the width of the localized states increases.     

Formation of oxide phases in the system Fe2O3-NiO

Mixed metal oxides in the system Fe₂O₃-NiO were prepared by coprecipitation of Fe(OH)₃/Ni(OH)₂ and the thermal treatment of hydroxide coprecipitates up to 800 or 1100°C. X-ray diffraction showed the presence of -Fe₂O₃, NiO and NiFe₂O₄ in samples prepared at 800°C. The oxide phases -Fe₂O₃, NiO, NiFe₂O₄ and a phase with structure similar to NiFe₂O₄ were found in samples prepared at 1100°C. Fourier transform-infrared spectra of oxide phases formed in the system Fe₂O₃-NiO are discussed. Two very strong infrared bands at 553 and 475 cm^–1, a weak intensity infrared band at 383 cm^–1 and two shoulders at 626 and 441 cm^–1 were observed for -Fe₂O₃ prepared at 1100°C. NiFe₂O₄, prepared at the same temperature, showed two broad and very strong infrared bands at 602 and 411 cm^–1, while NiO showed a broad infrared band at 466 cm^–1. Fourier transform infrared spectroscopic results were in agreement with X-ray diffraction.     

Low-loss,high-purity (TeO<Subscript>2</Subscript>)<Subscript>0.75</Subscript>(WO<Subscript>3</Subscript>)<Subscript>0.25</Subscript> glass

By melting a mixture of high-purity oxides in a platinum crucible under flowing purified oxygen, we have prepared (TeO₂)_0.75(WO₃)_0.25 glass with a total content of 3d transition metals (Fe, Ni, Co, Cu, Mn, Cr, and V) within 0.4 ppm by weight, a concentration of scattering centers larger than 300 nm in size below 10² cm⁻³, and an absorption coefficient for OH groups (λ ∼ 3 μm) of 0.008 cm⁻¹. The absorption loss in the glass has been determined to be 115 dB/km at λ = 1.06 μm, 86 dB/km at λ = 1.56 μm, and 100 dB/km at λ = 1.97 μm. From reported specific absorptions of impurities in fluorozirconate glasses and the impurity composition of the glass studied here, the absorption loss at λ ∼ 2 μm has been estimated at ≤100 dB/km. The glass has been drawn into a glass-polymer fiber, and the optical loss spectrum of the fiber has been measured.     

Dispersion analysis of asymmetric band shapes: Application to the IR absorption spectrum of silica glass

The IR absorption spectrum of silica glass in the 3800 to 8000 cm^–1 region is analyzed based on the assumption of asymmetric band shapes. For simulating the asymmetric band shapes, a generalized version of the convolution model for the complex dielectric constant is proposed that involves different magnitudes of the standard deviation for an oscillator distribution in the wavenumber regions below and above the distribution center. A computational program for the dispersion analysis of the absorption spectra using such a model is developed. Best fit to the IR spectrum of silica glass obtained with the asymmetric band shapes contains no systematic errors throughout the contours of the 4400–4600 and 7000– 7300 cm^–1 absorption maxima, thus having appreciably better quality than fits obtainable with the symmetric band shapes inherent in the usual convolution model. A high accuracy of simulating the 7000–7300 cm^–1 absorption maximum with the asymmetric band shapes is attained when using as few as two bands in this region, which is in contrast to available literature sources assuming four bands. The band frequencies and intensities calculated with the asymmetric and symmetric band shapes are compared.     

Optical study of the Zn-substitution effect on phonon anomalies and spin gap in underdoped YBa2Cu3Oy

Performing optical reflectivity measurements with the electric field vector parallel to the c-axis of Zn-substituted, oxygen deficient YBa₂Cu₃O_y single crystals, we find a strong Zn-substitution effect on the anomaly of the inplane oxygen bending mode at 320 cm^–1 and the new absorption band at 450 cm^–1, which are observed in underdoped, non-substituted crystals. Contrary to that, the low-frequency suppression of the conductivity is almost not affected. We conclude that the phonon anomaly and the absorption band are related to each other, but that the suppression of the conductivity is an independent phenomenon. Moreover, the present work could be strong evidence for a model where some phonons couple to antiferromagnetic fluctuations at the (, )-point leading to anomalous behaviour of these phonons when a spin gap opens.on leave from Institut für Technische Physik,Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe Germany     

Preparation of cobalt oxide films by plasma-enhanced metalorganic chemical vapour deposition

Co oxide films were prepared on glass substrates at 150–400°C by plasma-enhanced metalorganic chemical vapour deposition using cobalt (II) acetylacetonate as a source material. NaCl-type CoO films were formed at low O₂ flow rate of 7cm³ min^–1 and at a substrate temperature of 150–400°C. The CoO films possessed (100) orientation, independent of substrate temperature. Deposition rates of the CoO films were 40–47 nm min^–1. The CoO film deposited at 400 °C was composed of closely packed columnar grains and average diameter size at film surface was 60 nm. At high O₂ flow rate of 20–50 cm³ min^–1, high crystalline spinel-type Co₃O₄ films were formed at a substrate temperature of 150–400°C. The Co₃O₄ film deposited at 400°C possessed (100) preferred orientation and the film deposited at 150°C possessed (111) preferred orientation. Deposition rates of the Co₃O₄ films were 20–41 nm min^–1. Both Co₃O₄ films with (100) and (111) orientation had columnar structure. The shape and average size of the columnar grains at the film surface were different; a square shape and 35 nm for (100)-oriented Co₃O₄ film and a hexagonal shape and 60 nm for (111)-oriented film, respectively.     

Infrared and Structural Properties of Y1?xNdxBa2Cu3O7?δ (0 ≤ x ≤ 1)

Infrared and structural properties of Y_1–x Nd _x Ba₂Cu₃O_7– (0 x 1) were investigated using infrared absorption spectroscopy and X-ray powder diffraction. The unit cell parameters of the samples were defined using X-ray diffraction data. The resistance measurements showed that the samples revealed superconductivity in the temperature range of 80–100 K. It was observed that by the substitution of Nd to Y in YBa₂Cu₃O_{7 –} IR band at 573 cm^–1 that is assigned as Cu–O axial antisymmetric stretching mode shifts to 533 cm^–1 while the band at 620 cm^–1 that is due to Cu–O symmetric stretching mode in YBa₂Cu₃O_7– shifts to 588 cm^–1.     

Structure and crystallization behaviour of Li2O-Fe2O3-SiO2 glasses

Iron-containing lithium disilicate glasses, other silicate and borate glasses, and crystallized lithium disilicate glasses have been studied by Raman spectroscopy, luminescence spectroscopy and X-ray diffraction. In the as-quenched glasses the presence of iron leads to a strong Raman band at 950 cm^–1 and to a broad Raman scattering continuum below 500cm^–1. There is also an emission due to trivalent iron at about 14000cm^–1 Lithium metasilicate has been identified in all crystallized glasses with more than 1% Fe₂O₃. It was possible to crystallize some of the glasses by irradiating them with intense blue laser light, and Raman spectra of various stages of photocrystallization have been obtained. By comparing the Raman spectra of the crystallized glasses with those of as-quenched glasses it is deduced that the trivalent iron has its own distinct local environment in the glass.     

Effect of Electron Irradiation on the 77-K Band Gap of Rutile

The diffuse reflectance spectrum of powder TiO₂ (rutile) is measured from 0.36 to 0.9 m at 77 K before and after electron irradiation. The 77-K band gap of rutile is determined to be 3.0–3.02 eV. Irradiation with 30-keV electrons to a fluence of 10¹⁷ cm^–2 has no effect on the band gap of rutile. Reflectance data attest to the presence of two absorption bands near the intrinsic edge. The strength of these absorptions correlates with the radiation hardness of rutile.     

Study of Mechanical Activation of Diopside in a CO2 Atmosphere

Interaction of natural diopside CaMgSi₂O₆ with CO₂ during mechanical activation in a CO₂ atmosphere has been studied. It has been shown that, depending on the kind of mechanical activator used, two types of CO₂ sorption by diopside are possible. If grinding is not accompanied by crystal structure disordering, the sorption of CO₂ on the diopside surface is similar to the sorption on metal oxides in the form of undistorted CO₃ ^2– groups, resulting in a nonsplit absorption band at 1430 cm^–1 in the infrared spectrum. If the mechanical activation of diopside leads to amorphization of the sample, it absorbs CO₂ in the form of distorted carbonate groups, which results in the appearance of a double carbonate band with maxima at 1433 and 1522 cm^–1 in the infrared spectrum of the ground sample. This band is similar to the one corresponding to CO₃ ^2– groups in the infrared spectra of carbonate-containing silicate glass. The carbonate content in the diopside sample reaches about 15% CO2 (or 35% CaCO₃) after mechanical activation in an AL-1000 activator in the CO₂ atmosphere for 580 min. X-ray diffraction, infrared spectroscopic data, carbonate content, and BET surface area measurements indicate that CO₂ molecules are likely to penetrate the structurally disordered diopside sample by a tribosorption mechanism. The results on the relaxation of the activated diopside sample during heating are presented.     

Structural and physical characterization of the Li2O∶P2O5∶CrO1.5 ion-conducting glasses

Li₂OP₂O₅CrO_1.5 glasses containing 40, 50 and 60 mol% Li₂O and a varying P₂O₅-to-CrO_1.5 ratio have been synthesized. The glass-transition temperature and density increase as P₂O₅ is progressively replaced by CrO_1.5. The glasses, being green in colour and showing strong optical absorption at 450 nm and 660 nm, contain predominantly Cr^{3 +} ions and a relatively small amount of Cr^{6 +} ions. The proportions of phosphate species with one, two, and three non-bridging oxygen atoms are determined from Raman spectroscopy results. From X-ray photoelectron spectroscopy (XPS) binding energies of the Li 1s, P 2p, Cr 2p and O 1s core levels are determined. The O 1s spectrum is found to consist of two peaks which are attributed to the P=O, P-O-P, P-O, P-O-Cr, and Cr-O oxygen species. Conductivity of these glasses increases with increasing Li₂O content and with progressive replacement of P₂O₅ by CrO_1.5. The 0.60Li₂O O.32P₂O₅0.08 CrO_1.5 glass is found to have the highest conductivity, 3.2×10^–6–1 cm^–1 at 25 °C. Compositional dependence of the conductivity is discussed in relation to variations in the glass structure.     

Vibrational modes in electrodeposited amorphous silicon: FT-IR analysis

Infrared spectra of 13 samples of amorphous silicon bonded with hydrogen, fluorine and carbon, prepared by electrodeposition using a mixture of ethylene glycol and fluosilicic acid were analysed in the wave number region 4000-400 cm^–1 with a Fourier transform infrared spectrometer. Strong absorption peaks were observed at 1000 cm^–1 due to the SiF_x stretching mode. Small peaks were seen around 2300 and 640 cm^–1 due to SiH stretching and wagging modes of absorption. The number of bonded hydrogen atoms in the film deposited at 0.05 M, 50 mA cm^–2 was calculated to be 6.2579×10²¹ and 1.2302×10²⁰ atm cm^–3 using integrated absorption of the CH and SiH stretching modes, respectively. The absorption coefficient around the SiF_x stretch region was found to vary from 1300–2500 cm^–1 as the molarity of the electrolyte was increased. Binding energy shifts in X-ray photoelectron spectrum were used as a cross check to confirm the silicon bonding with carbon, hydrogen, oxygen and fluorine atoms. The absence of columnar growth in SEM photographs indicates no polysilane formation in the films.     

Specific absorption coefficient of chromium in (TeO<Subscript>2</Subscript>)<Subscript>0.80</Subscript>(MoO<Subscript>3</Subscript>)<Subscript>0.20</Subscript> glass

We have prepared (TeO₂)_0.80(MoO₃)_0.20 glass samples containing 0.01 to 0.11 wt % chromium and determined their optical transmission in the range from 450 to 2800 nm. The glasses have been shown to have a strong absorption band centered at 660 nm. From the attenuation coefficient as a function of Cr³⁺ concentration in the glasses, we have evaluated their specific absorption coefficient, which has been shown to be 190 ± 2 cm^–1/wt % at the maximum of the absorption band.     

Photoinduced changes in Raman spectra of YBa2Cu3O6.4 films

The evolution of Raman spectra with illumination has been studied in YBa₂Cu₃O_6.4 films at temperatures between 5–300 K. Low laser power has always been used to avoid local overheating, which was controlled by measuring the local temperature by the Stokes/anti-Stokes ratio. Three important photoinduced effects have been found: (i) the enhancement of the intensity of the observed phonon modes: (Cu(2) at 141 cm^–1, O(2)-O(3) at 338 cm^–1, and O(4) at 488 cm^–1), which may be related to the ordering of oxygen vacancies, (ii) the increase of the electronic scattering background for low Raman frequencies, which is in agreement with the enhancement of the static conductivity(0) after illumination, and (iii) the suppression of the intensity of the two-magnon band, which may be caused by the increase of charge carriers due to photodoping.     

Effect of Oxygen Doping on the IR Transmission and Cathodoluminescence of ZnSe

The effect of oxygen doping (0.9 and 4.3 vol % O₂in the gas phase) on the transmission and cathodoluminescence of CVD ZnSe was studied. The incorporation of oxygen was found to reduce the transmission in the spectral range 700–1900 cm^–1. Examination by scanning electron microscopy shows that Se excesses and high O₂concentrations lead to tabular growth. ZnO precipitation at structural defects during cooling was observed only in the end portion of the deposit. The dimensions of microinhomogeneities are shown to have a significant effect on the transmission of ZnSe. The oxygen-containing species present in the deposits were identified using cathodoluminescence spectra. The CL spectrum of Se-enriched p-type ZnSe is dominated by the band at 490 nm (SAL) at 80 K and the band at 640 nm (SA) at 300 K. The 640-nm band is attributed to recharging of the SALcenters upon a variation of the Fermi energy with temperature. Decreasing the Se excess leads to the quenching of the SALemission and appearance of the shorter wavelength component of the SAband at 600 nm (80–300 K), characteristic of slightly Zn-enriched ZnSe. The intensity of the self-activated bands is shown to increase as the concentration of dissolved oxygen increases.     

An infrared study of the structure of GeO2-CeO2 thin films

The infrared spectra of amorphous thin films consisting of GeO₂ co-evaporated with CeO₂ are presented and interpreted in relation to the spectrum of the pure amorphous GeO₂ film. The lower frequency side of the broad absorption band within this spectrum peaking at 730 cm^–1 is believed to be due to defect centres similar to the O ₁ ^– and O ₃ ⁺ centres found in a-SiO₂. Absorption at higher frequencies within this band is due to the O stretch vibrations of the Ge-O-Ge linkage. After considering the vibrations of the O ₁ ^– and O ₃ ⁺ centres in detail, it is shown that the band at 495 cm^–1 cannot be due to either of these centres and must therefore by caused by some other reactive defect centres. The variation of the position of the 730 cm^–1 peak within the series of spectra is noted and probable explanations are offered. The optical absorption edge of a-GeO₂ thin film is compared with that of a-SiO and a possible explanation of the basic differences is proposed.     

Compositional dependence of infrared absorption spectra studies for TeO2-P2O5 and TeO2-P2O5-Bi2O3 glasses

The infrared absorption spectra of the vitreous TeO₂-P₂O₅ and Bi₂O₃-TeO₂-P₂O₅ systems are studied in the spectral region of 4000 to 200 cm^–1. Absorption bands in this range are assigned. The midband wavenumber and the absorption intensity for the attributed bands are found to be strongly and systematically dependent on glass composition. Quantitative analysis was also attempted to justify our attribution of the observed bands.