Showing papers on "Infrared spectroscopy published in 1986"
TL;DR: In this paper, the authors reviewed work on In2O3:Sn films prepared by reactive e−beam evaporation of In2 O3 with up to 9 mol'% SnO2 onto heated glass.
Abstract: We review work on In2O3:Sn films prepared by reactive e‐beam evaporation of In2O3 with up to 9 mol % SnO2 onto heated glass. These films have excellent spectrally selective properties when the deposition rate is ∼0.2 nm/s, the substrate temperature is ≳150 °C, and the oxygen pressure is ∼5×10−4 Torr. Optimized coatings have crystallite dimensions ≳50 nm and a C‐type rare‐earth oxide structure. We cover electromagnetic properties as recorded by spectrophotometry in the 0.2–50‐μm range, by X‐band microwave reflectance, and by dc electrical measurements. Hall‐effect data are included. An increase of the Sn content is shown to have several important effects: the semiconductor band gap is shifted towards the ultraviolet, the luminous transmittance remains high, the infrared reflectance increases to a high value beyond a certain wavelength which shifts towards the visible, phonon‐induced infrared absorption bands vanish, the microwave reflectance goes up, and the dc resisitivity drops to ∼2×10−4 Ω cm. The corre...
2,124 citations
TL;DR: It is found that a standard, widespread, chemical-preparation method for silicon, oxidation followed by an HF etch, results in a surface which from an electronic point of view is remarkably inactive, which has implications for the ultimate efficiency of silicon solar cells.
Abstract: We have found that a standard, widespread, chemical-preparation method for silicon, oxidation followed by an HF etch, results in a surface which from an electronic point of view is remarkably inactive. With preparation in this manner, the surface-recombination velocity on Si111g is only 0.25 cm/sec, which is the lowest value ever reported for any semiconductor. Multiple-internal-reflection infrared spectroscopy shows that the surface appears to be covered by covalent Si-H bonds, leaving virtually no surface dangling bonds to act as recombinatiuon centers. These results have implications for the ultimate efficiency of silicon solar cells.
910 citations
TL;DR: In this paper, the local atomic structure of silicon suboxide (SiOx, x < 2) thin films using infrared (IR) spectroscopy was studied using PECVD of silane (SiH4) and nitrous oxide (N2O) mixtures, which were then diluted with He.
Abstract: We have studied the local atomic structure of silicon suboxide (SiOx, x<2) thin films using infrared (IR) spectroscopy. The films were prepared by plasma enhanced chemical vapor deposition (PECVD) of silane (SiH4) and nitrous oxide (N2O) mixtures, which were then diluted with He. The IR spectra were found to vary significantly with the degree of He dilution. Films grown with no He showed SiN, NH, and SiH bonding groups in addition to the three characteristic vibrations of the Si–O–Si linkage. The addition of He reduced the strength of the SiN, NH, and SiH absorption bands, and resulted in systematic increases in the frequency of the Si–O–Si asymmetric stretching vibration. The frequency of this Si–O–Si stretching vibration scales linearly with the oxygen concentration from approximately 940 cm−1 in oxygen doped amorphous silicon to 1075 cm−1 in stoichiometric noncrystalline SiO2. A deposition temperature of 350 °C and a He dilution of 50% gave a film composition close to SiO1.9. We propose a model for the...
738 citations
TL;DR: This chapter describes the basic principles, techniques, and applications of resolution-enhanced Fourier transform infrared spectroscopy, which provides several advantages over conventional dispersive techniques: higher resolution, sensitivity, signal-to-noise ratio (S/N), and frequency accuracy.
Abstract: Publisher Summary This chapter describes the basic principles, techniques, and applications of resolution-enhanced Fourier transform infrared spectroscopy. Infrared spectroscopy constitutes one of the oldest methods for studying the secondary structure of polypeptides and proteins. Polypeptides and proteins exhibit a total of nine characteristic absorption bands in the infrared region. These are usually termed the amide A, B, and amide I-VII bands. The amide I (∼1630-1690 cm -1 ) band is the most useful for protein structure studies by infrared spectroscopy. The use of Fourier transform infrared spectroscopy (FTIR) has led to major improvements in this regard. In principle, FTIR provides several advantages over conventional dispersive techniques: higher (1) resolution, (2) sensitivity, (3) signal-to-noise ratio (S/N), and (4) frequency accuracy. Any one of the first three advantages can be emphasized at the expense of the other two. For protein structure studies, high sensitivity makes it possible to acquire usable infrared spectra of aqueous solutions; such spectra are always notoriously difficult to obtain.
698 citations
TL;DR: T theory on the quantitative birefringence dispersions of liquid crystals was developed and found to have excellent agreement with experimental results throughout the entire visible and infrared spectral regions.
Abstract: The origins of liquid-crystal birefringence were investigated. Theory on the quantitative birefringence dispersions of liquid crystals was developed and found to have excellent agreement with experimental results throughout the entire visible and infrared spectral regions. New guidelines for selecting or synthesizing the liquid crystals with the desired birefringence are established. Novel applications of liquid crystals in the infrared region are foreseeable.
418 citations
01 Feb 1986
TL;DR: The first observation of a vibrational spectrum of a monolayer of molecular adsorbates by infrared-visible sum frequency generation is reported, paving the way for future dynamic studies of surface phonons and molecular vibrations.
Abstract: We report the first observation of a vibrational spectrum of a monolayer of molecular adsorbates by infrared-visible sum frequency generation. The results pave the way for future dynamic studies of surface phonons and molecular vibrations.
369 citations
Journal Article•
TL;DR: In this paper, a series of natural rhyolitic obsidians were analyzed for their total water contents by a vacuum extraction technique using several infrared and near-infrared absorption bands.
Abstract: A series of natural rhyolitic obsidians were analyzed for their total water contents by a vacuum extraction technique. The grain size of the crushed samples can significantly affect these analyses. Coarse powders must be used in order to avoid surface-correlated water. These analyses were used to calibrate infrared spectroscopic measurements of water in glass using several infrared and near-infrared absorption bands. We demonstrate that infrared spectroscopy can yield precise determinations of not only total dissolved water contents, but also the concentrations of individual H-bearing species in natural and synthetic rhyolitic glasses on spots as small as a few tens of micrometers in diameter.
362 citations
TL;DR: Les resultats d'etudes precedentes sur les polyamides amorphes sont applicables a ce polymere semi-cristallin this paper, i.e.
Abstract: Les resultats d'etudes precedentes sur les polyamides amorphes sont applicables a ce polymere semi-cristallin
358 citations
351 citations
TL;DR: In this article, the feasibility of Fourier transform Raman spectroscopy has been investigated and a single instrument for both spectroscopies both convenient and cost-effective has been proposed.
Abstract: There has long been a widespread interest in the feasibility of Fourier transform Raman spectroscopy. The well-deserved reputation of FT-IR has generated hopes for similar benefits in Raman spectroscopy, and the complementarity of IR and Raman spectroscopy has made the use of a single instrument for both spectroscopies both convenient and cost-effective.
351 citations
TL;DR: The effect of sulfur promotion on the generation of strong acidity on ZrO/sub 2, TiO/Sub 2, Fe/sub O/sub 3, Al/sub S 2 O/S 3, SnO/S 2, and Bi O/O/3 was examined by the isomerization of cyclopropane and by infrared spectroscopy as discussed by the authors.
Abstract: The effect of sulfur promotion on the generation of strong acidity on ZrO/sub 2/, TiO/sub 2/, Fe/sub 2/O/sub 3/, Al/sub 2/O/sub 3/, SnO/sub 2/, SiO/sub 2/, and Bi/sub 2/O/sub 3/ was examined by the isomerization of cyclopropane and by infrared spectroscopy. The acidity generated varied on the types of oxides. The highest promotion effect was found in the cases of ZrO/sub 2/, TiO/sub 2/, and Fe/sub 2/O/sub 3/, while a lower effect was observed for Al/sub 2/O/sub 3/ and SnO/sub 2/, and no effect was found for SiO/sub 2/ and Bi/sub 2/O/sub 3/. Infrared spectroscopic observation indicates the presence of the surface sulfur complex having covalent SO double bonds on all of the sulfur-promoted oxides. An admission of pyridine resulted in a remarkable shift in an asymmetric stretching frequency of S=O bonds in the cases of ZrO/sub 2/, TiO/sub 2/, and Fe/sub 2/O/sub 3/; however, a small shift was found on Al/sub 2/O/sub 3/, and no shift was found on SiO/sub 2/ and Bi/sub 2/O/sub 3/. The magnitude of this shift was well-correlated with the extent of the promotion effect. The drastic shift suggests that a change of electronic structure in the surface sulfur complex takes place by the adsorptionmore » of basic molecules. The origin of the generation of the strong acidity by a sulfur promotion is the formation of the surface sulfur complex which has a covalent SO double bond on one hand and a strong tendency of losing its double-bond character or decreasing the bond order of SO by an electronic shift from a basic molecule adsorbed to the sulfur complex on the other.« less
TL;DR: In this paper, the transformation with temperature of SiO2 gels has been studied using IR spectroscopy together with measurements of density and specific surface area, thermal analysis and SEM, and the IR spectra of these gels, measured as a function of temperature and H2O/TEOS ratio, confirm that the relative concentration of OH groups is temperature dependent.
Abstract: Silica gels were prepared from alcoholic solutions of tetraethylorthosilicate (TEOS) with different H2O/TEOS molar ratios In the present work the transformation with temperature of these gels has been studied using IR spectroscopy together with measurements of density and specific surface area, thermal analysis and SEM The IR spectra of these gels, measured as a function of temperature and H2O/TEOS ratio, confirm that the relative concentration of OH groups is temperature dependent The total OH content, also depends on the H2O/TEOS ratio in the gel The combined results of IR, density and specific surface area measurements allow some structural considerations to be advanced about the final SiO2 glasses obtained
TL;DR: In this paper, the infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H 2, have been observed.
Abstract: Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm^−1, with a resolution of 1.2 cm^−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O + 3 and H9O + 4 .
Book•
01 Jan 1986
TL;DR: The application of Raman Spectral Spectroscopy in Structural Studies of Viruses, Nucleo-proteins and their Constituents Drug-Nucleic Acid Interactions Normal Analysis of Large Molecules of Biological Interest: Metalloporphyrins and Lumiflavin Resonance.
Abstract: Resolution Enhancement of Infrared Spectra of Biological Systems Peptide Backbone Conformation and Microenvironment of Protein Side Chains Raman and UV Resonance Raman Spectra of Proteins and Related Compounds Local Conformations and Polymorphism of DNA Duplexes as revealed by their Raman Spectra Applications of Raman Spectroscopy in Structural Studies of Viruses, Nucleo-proteins and their Constituents Drug-Nucleic Acid Interactions Normal Analysis of Large Molecules of Biological Interest: Metalloporphyrins and Lumiflavin Resonance Raman Spectroscopy of Flavins and Flavoproteins Resonance Raman Spectra of Reaction Intermediates of Heme Enzymes.
TL;DR: The results indicated that the absorbance at 930 cm-, attributed to 3,6-anhydrogalactose, was also related to content of galactose-4-sulfate in agars and carrageenans.
Abstract: The sulfate content of carrageenans and agars was obtained from characteristic infrared absorbance bands. The absorbance at 2920 cm\" attributed to C-H was used äs an index for total sugar content. Sulfate was determined from the following absorbance ratios: total sulfate 1250/2920, galactose-4-sulfate, 845/2920, 930/ 2920, and 3,6-anhydrogalactose-2-sulfate, 805/2920. The results indicated that the absorbance at 930 cm-, attributed to 3,6-anhydrogalactose, was also related to content of galactose-4-sulfate in agars and carrageenans.
TL;DR: In this paper, the structure of the hydrogen-saturated Si(100 and Ge(100) surfaces was studied by means of high-resolution surface infrared spectroscopy. And they found that the Si surfaces saturated with H at room temperature, characterized by a (1×1) LEED pattern, are made up of a disordered arrangement of subunits formed of both mono- and di-hydrides.
TL;DR: In this article, a detailed study of the IR spectrum of goethite is given with the aim of relating variations to crystalline order and particle size, and two different bending modes exist from site group splitting, their active modes from factor group splitting are at lower frequencies than the uncoupled ones.
Abstract: A detailed study of the IR spectrum of goethite is given with the aim of relating variations to crystalline order and particle size. The OH stretching vibrations are split into two active components at high frequency, plus two inactive ones at low frequency. Two different bending modes exist from site group splitting. Their active modes from factor group splitting are at lower frequencies than the uncoupled ones. The lattice bands at 630 and 400 cm−1 correspond to Fe-O or Fe-OH stretching, approximately parallel to a and c, and thus respectively sensitive and not sensitive to the particle shape, as long as it remains elongated along c.
Journal Article•
TL;DR: In this paper, the authors obtained infrared and Raman spectra for Si02-H20 glasses with low (1200 ppm) and high (6.3 wt%) water contents.
Abstract: There is some interest in the speciation of water in silicate glasses and melts, and the effect of bulk composition on this speciation. We have obtained infrared and Raman spectra for Si02-H20 glasses with low (1200 ppm) and high (6.3 wt%) water contents. The lowwater-content glass shows an asymmetric band in the fundamental O-H stretching region, consistent with an SiOH species involved in a range of hydrogen-bonding environments. The high-water-content sample shows features due to both hydroxyl groups, as observed for the low-water-content glass, and molecular H20 dissolved in the glass. This sample also shows a Raman band at 3598 cm-i, which probably corresponds to a new type of SiOH species. We have also obtained the Raman spectrum for a sodium silicate glass Na20' 4Si02 containing 1 wt% H20. Addition of water to this composition causes considerable changes in the silicate band region below 1200 em-i. The O-H stretching bands are very different to those observed for the Si02-H20 glasses, and a weak band near 2350 cm-1 may correspond to SiOH groups involved in intratetrahedral hydrogen bonding, across an edge of the Si04 tetrahedron.
TL;DR: In this paper, the presence of internal silanols in ZSM-5 was found to increase as aluminium content decreases and they are believed to be responsible for the phenomenon of excess ion exchange previously reported.
TL;DR: In this article, the lattice vibrations of Ba(Zn,Ta)O3 and BaZrO3 solid solutions, far infrared reflection spectra were measured from 50 to 4000 cm−1 using a Fourier transform infrared spectrometer.
Abstract: The dielectric ceramic materiala Ba(Zn1/3Ta2/3)O3–BaZrO3 has extremely low dielectric loss at microwave frequencies. To investigate the lattice vibrations of Ba(Zn,Ta)O3 and Ba(Zr, Zn, Ta)O3 solid solutions, far infrared reflection spectra were measured from 50 to 4000 cm−1 using a Fourier transform infrared spectrometer. These data were analyzed according to the classical dispersion theory. The spectra of Ba(Zn,Ta)O3 are well fitted by using the 14 resonant modes, and the spectra of Ba(Zr, Zn, Ta)O3 solid solution are fitted by assuming the normal distribution on resonant frequencies. The damping constant of these materials is discussed, and the values of tan δ calculated from the dispersion parameters agree with the measured values.
TL;DR: The first homodinuclear macrocyclic lanthanide complexes were obtained as compounds of the 2:2 Schiff base formed by condensing 2,6-diformyl-p-cresol and triethylenetetramine (L7) by a template procedure using lanthanides nitrates and perchlorates.
TL;DR: In this paper, the B9 peak is attributed to carbon-carbon bond vibrations of atoms within the platelet, and it is suggested that other localized mode absorptions seen in type I a spectra may be attributed to vibrations of N-C and N-N-N bonds of atoms in the platelets.
Abstract: The B9 localized mode, infrared absorption peak (which is due to {100} platelets) and its relations with other features in the infrared absorption spectrum of type la diamonds have been investigated. It is recognized that it is possible, on the basis of their one-phonon infrared absorption spectra, to separate type la diamonds into two categories. In ‘regular’ diamonds, there is a strict proportionality between the strength of the B9 peak and the strength of the lattice absorption due to B nitrogen aggregates; this is interpreted to be indicative of an epoch of smooth, undisturbed conversion of A nitrogen aggregates (or pairs of N atoms) to B aggregates, with the concurrent nucleation and growth of platelets. For ‘irregular’ diamonds this proportionality does not hold, and such specimens are recognized as crystals in which a catastrophic degradation of some or all of the platelets has occurred. It is argued that the proportionality observed for the regular specimens implies that nitrogen cannot be the dominant atomic species in the platelets, and a mechanism is described for platelet production by the formation and aggregation of carbon interstitials. Platelets are here seen as a necessary, but incidental, product of the nitrogen aggregation sequence. The B9 peak is ascribed to carbon-carbon bond vibrations of atoms within the platelet. The presence of N atoms as a minority species in the platelets is discussed, and it is suggested that other localized mode absorptions seen in type I a spectra may be attributed to vibrations of N-C and N-N bonds of atoms in the platelets. The B9 peak strength is also found to be linearly proportional to the recently-discovered D component of the lattice absorption spectrum, for both regular and irregular specimens. The D absorption is thus attributed to platelet-stimulated lattice vibrational modes. Among regular specimens, the strength of the N3 optical absorption is proportional to the B9, and hence also B, absorption strengths. The N3 centres are considered to result from minor side reactions occurring during the epoch of conversion of A centres to B centres.
TL;DR: In this paper, the authors investigated the temperature evolution of the structure of silica thin films by Fourier Transform Infrared (FTIR) Spectroscopy and found that the removal of water from the pores and gel surface is easier when the gels are prepared in basic conditions.
Abstract: In this work we investigated the temperature evolution of the structure of silica thin films by Fourier Transform Infrared (FTIR) Spectroscopy. The gels, prepared by hydrolysis and polycondensation in the presence of an excess of water to tetramethoxysilane, were thin enough to be studied in transmission. It was found that the removal of water from the pores and gel surface is easier when the gels are prepared in basic conditions. During the drying heat treatment, residual methanol oxidizes and produces formaldehyde, formic acid and formates. These species are still present in the gel at 300 °C.
TL;DR: In this paper, the strength of acidity of bridging OH groups increases with the Si/Al ratio from 1.4 to 7 but remains constant above Si/al ~10, and two signals of acidic hydroxyl protons observed in zeolites HY are correlated with the so-called high and low frequency band in infrared spectroscopy.
TL;DR: In this paper, the fusion de couches monomoleculaires de composes organiques amphiphiles sur support solide, and fondees sur des etudes de spectroscopie IR a transformation de Fourier and des mesures de mouillage.
Abstract: Donnees sur la fusion de couches monomoleculaires de composes organiques amphiphiles sur support solide, fondees sur des etudes de spectroscopie IR a transformation de Fourier et des mesures de mouillage
TL;DR: In this article, the infrared absorption intensities of linear CO(a) derived from CO, CH3OH and HCOOH, respectively, on a platinum electrode in 0.5 M H2SO4 were determined as a function of the total adsorbate coverage.
TL;DR: In this article, the Bruggeman effective medium theory was used to average over the vibrational properties of five basic Si-centered tetrahedra, whose relative occurrence was given by the stoichiometry, and the complex dielectric function e was extracted by computation.
Abstract: Films of SiOxNy, with 0.25≲x≲2 and 0
TL;DR: The electrical conductivity of the redoped polythiophene films was in the range 2 × 10 2 − 5.9 S cm −1, where S is the number of conjugated coplanar segments.