IR Transmission Spectra Research Articles

Fabrication and optical characteristics of thick GeO2 sol–gel coatings

Thick, crack-free GeO2 sol–gel coatings were fabricated using tetraethylorthogermanate and polyvinylpyrrolidone as starting raw materials and investigated as the cladding material for hollow waveguide delivery of CO2 laser radiation. A favorable GeO2 coating solution was synthesized by adding PVP to a TEOG–ethanol solution under dry nitrogen atmosphere in a glove box. TEM and viscosity analyses showed the PVP chains adsorbed onto GeO2 particles capped the surface HO–Ge– groups of particles and provided steric hindrance against aggregation of particles resulting in a stable sol with a viscosity value of about 35mPas. TG-DTA analyses revealed that the densification of the GeO2 gel coatings with PVP progressed within a wide temperature range from room temperature to 650°C leading to the production of crack-free GeO2 coatings with a thickness of 4μm. The IR transmission spectra and XRD studies indicated that calcination of the coatings at 700°C for 60min in an oxygen atmosphere removed effectively the organic complexes and hydroxy groups and transformed the coatings into hexagonal GeO2 crystalline phase. The optical constants of the GeO2 coatings were extracted from the IR reflective spectra and the complex refractive index N of the coatings was determined to be 0.5631–0.8347i at 940cm−1. The theoretical transmission loss and the additional loss due to scattering from roughnesses of this material were calculated. The results showed the optic loss at the wavelength of CO2 laser based on the GeO2 coatings as the cladding material can be expected as low as 0.0556dB/m.

Effect of bismuth oxide introduction on spectroscopic properties of Er 3+/Yb 3+ co-doped aluminophosphate glasses

The absorption spectra, emission spectra and infrared spectra of Er 3+/Yb 3+ co-doped xBi 2O 3–(65 − x)P 2O 5–4Yb 2O 3–11Al 2O 3–5BaO–15Na 2O were measured and investigated. Spontaneous emission probability, radiative lifetime and branching ratios of Er 3+ were calculated according to the Judd–Ofelt theory. The role of substitution of Bi 2O 3 for P 2O 5 on luminescence of Er 3+/Yb 3+ co-doped aluminophosphate glasses has been investigated. The calculated radiative lifetimes ( τ rad) for 4I 13/2 and 4I 11/2 were decreasing with Bi 2O 3 content increases, whereas the measured total lifetime ( τ meas) for 4I 13/2 showed linearly increasing trends. The effect of Bi 2O 3 introduction on OH − groups was also discussed according to the IR transmittance spectra of glasses. It was found that FWHM of glasses were not affected with the substitution of Bi 2O 3 for P 2O 5. The emission spectra intensity increased with Bi 2O 3 content due to the decreases of phonon energy and OH − content in glasses.

IR-active vibrational modes of CdTe and CdSe colloidal quantum dots and CdTe/CdSe core/shell nanoparticles and coupling effects

The frequencies of the vibrational modes of CdTe and CdSe quantum dots and CdTe/CdSe core/shell nanoparticles prepared by the colloid chemistry method are determined using IR transmission and IR reflection spectroscopy. The experimental IR transmission spectrum of CdTe and CdSe nanocrystals exhibits a broad minimum located between the frequencies of the transverse optical (TO) and longitudinal optical (LO) phonons of bulk CdTe and CdSe crystals. The frequencies of the modes for ensembles of CdTe and CdSe quantum dots are considerably shifted toward lower frequencies as compared to those calculated for single quantum dots. This is explained by the dipole-dipole interaction between quantum dots. The frequencies of modes for the structures with core/shell nanoparticles differ little from the calculated frequencies. This suggests a weakening of the interaction in these structures due to the enhancement of dielectric screening.

Correlation between Ingot Diameter and Crystal Properties of CdZnTe:In Grown by the Modified Bridgman Method

The compound semiconductor CdZnTe:In is the most promising material for room temperature nuclear radiation detectors. Enlarging the diameter of CdZnTe:In ingot can improve the yield and reduce the production cost, which, however, affects the properties of CdZnTe:In to some extent. Recently, CdZnTe:In ingots of 30 mm and 60 mm diameter were grown by the modified vertical Bridgman method in our laboratory. The crystal properties of both ingots were compared according to etch pit density (EPD) of dislocation, X-ray rocking curve, IR transmission spectra, and photoluminescence (PL) spectra. For the CdZnTe:In ingot of 30 mm diameter, the EPD of dislocation was 2.1 × 104 cm-2, and was up to 1.9 × 105 cm-2 when the CdZnTe:In ingot diameter was enlarged to 60 mm. The full width at half-maximum (FWHM) of X-ray rocking also increased from 0.02014° to 0.02864° at the same time. The two phenomena imply that the crystalline quality of CdZnTe:In deteriorated with the enlarging of the ingot diameter. In addition, when t...

Infrared spectroscopic investigation and semi-empirical modeling of the structure of an adsorption complex formed with a nitroxide radical with functional groups

It is confirmed by means of infrared spectroscopy that adsorption of sulphur dioxide on the layers obtained on the basis of the nitroxide radical 2-(4′-dimethylaminophenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl results in the formation of the adsorption complex (AC). The IR transmission spectra of the layers exhibit shifts of the frequencies of normal vibrations of the perturbed SO 2 molecule in the adsorption complex, which suggests that this complex is formed at the oxyl group but not at the amine one, as it is the case with substituted amines. This is in good agreement with the results of semi-empirical modeling of the AC structure by means of MM2. It is demonstrated experimentally that the formation of AC is a reversible reaction at room temperature.

Investigation of the modified chemical vapor deposition in preparation of glasses in the SiO2-GeO2-F system

The compositions of fluorogermanosilicate glasses prepared by the modified chemical vapor deposition (MCVD) method are calculated in terms of equilibrium thermodynamics. The calculations are based on the assumption regarding the formation of a mixture of pure oxide particles. This assumption is confirmed by the IR transmission spectra of porous deposits.

Optical and electrical properties of indium-doped Cd 0.9Zn 0.1Te crystal

The indium-doped CdZnTe crystal was characterized by PL spectra at 10 K and IR transmission spectra, as well as its current–voltage behavior at room temperature. The results showed that indium atoms substituted for the Cd vacancy and produced ionized donors [In Cd] +, i.e. indium doping element recombined with [V cd] 2− and formed the singly negative defect complex A-center [ In Cd + V Cd 2 - ] - and the neutral ones [ 2 In Cd + V Cd 2 - ] 0 and [ In cd + ( In Cd + V Cd 2 - ) - ] 0 . Indium doping also increased the IR absorption of the CdZnTe crystal due to the lattice absorption and free-carrier absorption. Meanwhile, indium doping increased the electrical resistivity and decreased the leakage current of CdZnTe crystals remarkably.

An infrared study of pure and ion irradiated frozen formamide

Context. The chemical evolution of formamide (HCONH 2 ), a molecule of astrobiological interest that has been tentatively identified in interstellar ices and in cometary coma, has been studied in laboratory under simulated astrophysical conditions such as ion irradiation at low temperature. Aims. To evaluate the abundances of formamide observed in space or in laboratory, the integrated absorbances for all the principal IR features of frozen amorphous pure formamide deposited at 20 K were measured. Further evidence that energetic processing of ices occurring in space is extremely relevant both to astrochemistry and to astrobiology has been found, showing that new molecular species are synthesized by ion irradiation at a low temperature. Methods. Pure formamide were deposited at 20 K and IR transmission spectra measured for different ice thicknesses. The ice thickness was derived by looking at the interference pattern (intensity versus time) of a He-Ne laser beam reflected at an angle of 45 deg by the vacuum-film and film-substrate interfaces. Samples of formamide ice were irradiated with 200 keV H + ions and IR spectra recorded at different ion fluences. Results. New molecules were synthesized among which are CO, CO 2 , N 2 O, isocyanic acid (HNCO), and ammonium cyanate (NH 4 + OCN - ). Some of these species remain stable after warming up to room temperature.

Theoretical and experimental studies of the structure and intermolecular interactions in 2-biphenylmethanole

The crystalline structure of 2-biphenylmethanol has been investigated by the radiographic method at room temperature, and its IR transmission spectra were measured in the 400–4000 cm−1 range. Structural-dynamic models of free molecules of 2-biphenylmethanol, biphenyl and methanol, hydrogen-bonded complexes of 2-biphenylmethanol with methanol and a tetramer of methanol molecules have been built by the density functional method (B3LYP/6-31G*). The structure, the energy, mechanical and electro-optical parameters, the frequency and intensity of normal vibrations in IR spectra of each of the mentioned molecular systems were calculated. The crystalline structure of 2-biphenylmethanol, its features determined by the hydrogen bond formation in the crystal has been found, its structure-forming role and energy were assessed, and IR spectra interpreted on the basis of single crystal X-ray diffraction data, the analysis of measured IR spectra, and results of molecular modeling.

Effect of V 2O 5 on structure and electrical properties of zinc borate glasses

Glasses with the compositions xV 2O 5·(50 − x)ZnO·50B 2O 3 (Series I) and xV 2O 5· (50 − x)B 2O 3·50ZnO (Series II) with (0 ≤ x ≤ 20 mol%) have been prepared using normal melt quench technique. The IR transmission spectra of the glasses have been recorded over the range 400–4000 cm −1. The changes caused by the addition of V 2O 5 on the structure of these glasses have been studied. The values of theoretical optical basicity have also been calculated. The density and molar volume studies indicate that V 2O 5 in these glasses is acting as network modifier in place of network former. Values of the direct current electrical conductivity have been measured from 373 to 623 K and the activation energy has been calculated. The variations in density, molar volume and electrical conductivity with V 2O 5 content have been discussed in terms of changes in the glass structure.

Properties of Dy3+‐Doped Ge–As–Ga–Se Chalcogenide Glasses

In the present work, properties of Dy3+‐doped chalcogenide glasses as a stoichiometric formula of (0.9−x)GeSe2–xAsSe3/2–0.1GaSe3/2 (x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were investigated as a comparison with the previously studied Ge–Ga–Se system. Property measurements include differential thermal analysis, density, Vis‐NIR and IR transmission spectra, and fluorescent emission spectra. Judd–Ofelt analysis was performed using the calculated oscillator strengths of glasses. All properties of glasses show obvious dependence on compositions. Especially, the improved devitrification resistance and the longer fluorescence life at 1.34 μm emission were observed with the increasing As content. Noticeably, abnormal changes in some properties occurred to the glass whose average coordination number corresponds to the threshold of two‐dimensional–three‐dimensional topological phase transition.

Fabrication of polymeric PVDF/PDDA ultrathin films on quartz crystal microbalance

Polymeric PVDF/PDDA ultrathin films on quartz crystal microbalance (QCM) with Pt electrodes prepared by electrostatic layer-by-layer (LbL) self-assembly (SA) of each layer for 20 min were investigated. Physical measurements of deposited mass were performed with QCM. The composite structure films have been determined by IR transmittance spectra and gracing incident X-ray diffraction, and its surface morphologies under difference deposit period have been studied by an atomic force microscope (AFM). The results show a slippery and compact micro-scale PDDA/PVDF ultrathin films formed on QCM substrates after fifth period. In addition, the resistivity of the PDDA/PVDF multilayer films at room temperature is investigated.

Intense upconversion luminescence and effect of local environment for Tm 3+/Yb 3+ co-doped novel TeO 2–BiCl 3 glass system

We present the results of a study that uses theoretical and experimental methods to investigate the characteristics of the upconversion luminescence of Tm 3+/Yb 3+ codoped TeO 2–BiCl 3 glass system as a function of the BiCl 3 fraction. These glasses are potentially important in the design of upconversion fiber lasers. Effect of local environment around Tm 3+ on upconversion fluorescence intensity was analyzed by theoretical calculations. The structure and spectroscopic properties were investigated in the experiments by measuring the Raman spectra, IR transmission spectra, and absorption and fluorescence intensities at room temperature. The results indicate that blue luminescence quantum efficiency increases with increasing BiCl 3 content from 10 to 60 mol%, which were interpreted by the increase of asymmetry of glass structure, decrease of phonon energy and removing of OH − groups.

Structural, optical, physical and electrical properties of V 2O 5·SrO·B 2O 3 glasses

The present work aims to study the structure and variation of optical band gap, density and dc electrical conductivity in vanadium strontium borate glasses. The glass systems xV 2O 5·(40 − x)SrO·60B 2O 3 and xV 2O 5·(60 − x)B 2O 3·40SrO with x varying from 0 to 20 mol% were prepared by normal melt quench technique. Structural studies were made by recording IR transmission spectra. The fundamental absorption edge for all the glasses was analyzed in terms of the theory proposed by Davis and Mott. The position of absorption edge and hence the value of the optical band gap was found to depend on the semiconducting glass composition. The absorption in these glasses is believed to be associated with indirect transitions. The origin of Urbach energy is associated with the phonon-assisted indirect transitions. The change in both density and molar volume was discussed in terms of the structural modifications that take place in the glass matrix on addition of V 2O 5. dc conductivity of the glass systems is also reported. The change of conductivity and activation energy with composition indicates that the conduction process varies from ionic to polaronic one.

Effects of In doping on the properties of CdZnTe single crystals

An intrinsic CdZnTe ingot and an Indium (In) doped CdZnTe:In ingot were grown by the modified Bridgman (MB) method, respectively. The effects of In-doping on the properties of CdZnTe single crystals have been analyzed in detail. Leakage current–bias voltage ( I– V) measurement shows that the resistivity of CdZnTe increases three orders after In is introduced into the crystal, because cadmium (Cd) vacancies are effectively compensated by In. The leakage current in CdZnTe:In is stabilized more quickly compared with that in CdZnTe, revealed by leakage current–time ( I- t) measurement. IR transmission spectra of both ingots indicate that In-doping results in remarkable reduction of the IR transmission of CdZnTe crystals. Photoluminescence (PL) measurement shows that a new deep-level emission appears, due to an In-related complex, and the acceptor-bound (A 0,X) peak disappears in the case of CdZnTe:In. It confirms that Cd vacancies are completely compensated by the In-related complex, which is consistent with the result of the I– V measurement. In addition, the intensity of the donor–acceptor pair recombination (D, A) peak becomes stronger after In is introduced. It indicates that there still exists excess In in the crystal after Cd vacancies are completely compensated.

Formation and Properties of Chalcogenide Glasses in the GeSe2–As2Se3–CdSe System

The glass‐forming region in a GeSe2–As2Se3–CdSe system and the dependence of properties on glass compositions as a formula of 70GeSe2–(30−x)As2Se3–xCdSe (x=0–25) were investigated. Measurements included density, micro‐hardness, differential scanning calorimetry (DSC), X‐ray diffraction, and IR transmission spectra. A large glass‐forming region was shown while addition of Cd increases the crystallization trend of the system. Besides, the Cd content accommodated by the system to form glass is found to be lower in the As2Se3‐rich region than in the GeSe2‐rich region. With the introduction of CdSe, density, micro‐hardness, and Tg of glasses increase whereas an exothermal peak in the DSC curve appears and thermal stability (ΔT) decreases. The activation energy of crystallization and the Avrami exponent were also obtained using the modified Ozawa equation.

Structure and Electric Properties of Lithium Phosphate Glasses

The temperature-concentration dependence of the conductivity in glasses of the system Li2O-P2O5 was studied. The content of extrinsic hydrogen in the structure of glasses was estimated by IR transmission spectra. The effect of hydrogen on the electrical properties and structure of the glasses studied was considered.

Effect of hydroxyl groups on nonradiative decay of Er3+ : 4I13 / 2 → 4I15 / 2 transition in zinc tellurite glasses

A series of zinc tellurite glasses of 75TeO2–20ZnO–(5−x)La2O3–xEr2O3 (x=0.02, 0.05, and 0.1 mol%) with the different hydroxl groups were prepared by the conventional melt-quenching method. Infrared spectra were measured in order to estimate the exact content of OH− groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH− content concentration as evidenced by IR transmission spectra. Various nonradiative decay rates from 4I13/2 of Er3+ with the change of OH content were determined from the fluorescence lifetime and radiative decay rates were calculated on the basis of Judd–Ofelt theory.

The influences of ZnO doping concentration on structure and photorefractive properties of Zn:Fe:LiNbO3 crystals grown by TSSG method

In this paper, LiNbO3 crystals doped with same concentration of Fe2O3 and with different concentration of ZnO have been grown by the top-seeded-solution-growth (TSSG) method. Their IR transmittance spectra, UV–vis absorption spectra, lattice constants, and Curie temperature were measured. In two-wave coupling experiments, writing and erasure time constants, and maximum diffraction efficiency of the crystals were measured and compared with those of congruent LiNbO3 (CLN) crystals doped with same ions. The crystals grown by TSSG method show shorter writing time, erasure time, and lower diffraction efficiency than the CLN crystals. The influences of ZnO doping concentration on photorefractive properties are studied.

Infrared attenuated total reflection spectroscopy studies of aprotic condensation of (EtO)3Si[sbnd]R[sbnd]Si(OEt)3 and R[sbnd]Si(OEt)3 systems with carboxylic acids

Aprotic hydrolysis and condensation reactions of bis end-capped trialkoxysilanes ((EtO)3SiRSi(OEt)3), linked via the organic chain R containing urea groups chemically bonded to a poly(propyleneglycol) (PPG) chain, in the presence of carboxylic acids, i.e. acetic-, chlorodifluoroacetic- and trifluoroacetic acids, were studied using infrared attenuated total reflection (IR ATR) spectroscopy. IR and 29Si NMR spectral analysis revealed solvolysis reactions: the carboxylic acids interacted with ethoxysilane groups forming silyl esters leading to the formation of bridging SiOSi groups and carboxylic acid ester by-products. These results were compared with those obtained on simpler single capped methyltriethoxysilane (MeSi(OEt)3, MTEOS) condensed with trifluoroacetic acid. Gelation of (EtO)3SiRSi(OEt)3 (catalyzed with acetic acid) encapsulated between a transparent conductive oxide (TCO) glass and a conductive and IR transparent silicon wafer was followed with the help of IR reflection–absorption spectroscopy. The results revealed that aprotic solvolysis of the hybrid precursor with acetic acid led to the formation of non-aqueous gels with low silanol content, confirming the advantages of aprotic solvolysis of organic–inorganic hybrids used as redox electrolytes in hybrid electrochromic (EC) and dye-sensitized photoelectrochemical (DSPEC) cells. Some comments regarding the accuracy of IR ATR spectral measurements compared to IR transmission spectra are also given.