Search results for "amorphous"

<title>Nature of fundamental absorption edge of WO<formula><inf><roman>3</roman></inf></formula></title&…

1997

The fundamental absorption edge of amorphous, polycrystalline and crystalline tungsten trioxide (WO3) thin films obtained by different techniques (thermal evaporation, rf plasma sputtering, chemical gas transport) was investigated. Special attention was paid to correct measurements of absorption values of all WO3 thin films taking into account the scattered light, interference effects and reflection losses. The indirect edge at 2.70 eV was determined for crystalline WO3, but for crystal WO3:Ti the direct edge in the same place (2.72 eV) was found. For polycrystalline WO3 thin film first edge transition located at 2.76 eV had a quadratic dependence similar to the amorphous film at a higher p…

High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties

2000

AbstractHigh-quality crystalline Si1-xGex (x=0.10 and 0.25) alloys were implanted with 70 keV Er+ ions at temperatures of 350°C and 550°C to a fluence of 1015 cm−2. In-situ Rutherford backscattering/channeling (RBS) analysis supplemented with transmission electron microscopy (TEM) showed that as-implanted alloys were in form of ternary solid solutions with a peak Er concentration of 1 at.% without any trace of Er-Si or Er-Ge precipitation.In the samples implanted at 350°C Er atoms were found to be distributed randomly in the amorphous host matrix. Post-implantation annealing at different temperatures up to 600° showed that the solid phase epitaxial regrowth of the damaged layers strongly de…

Über die intensitätsabhängigkeit der ultrarotbanden von der temperatur und vom kristallisationsgrad

1961

Beim Erhitzen von Polyathylenen und Paraffin geben die amorphen Banden bei 7,68μ und 7,38μ die Abnahme des Kristallisationsgrades richtig wieder, die kristalline Bande bei 13,7μ zeigt dagegen eine uber das partielle Schmelzen hinausgehende, durch Torsionsschwingungen der Ketten im Kristallgitter bedingte Intensitatsabnahme. Beim Terylen zeigen alle von uns untersuchten kristallinen und amorphen Banden eine verschiedene Abhangigkeit von der Temperaturbewegung, wobei einige amorphe Banden beim Erhitzen sogar verschwinden. Bei Messungen bei konstanter Temperatur zeigen alle Banden im Verlauf einer Kristallisation eine ubereinstimmende Veranderung mit zunehmendem Kristallisationsgrad. At the he…

1979

2D NMR spectra have been measured at variable temperatures between −100°C and +110°C in a sample of melt crystallized deuterated polyethylene (PE). The line shape could be decomposed into a central part originating from deuterons in the amorphous regions and outer parts from crystalline regions of PE. The “NMR crystallinity” determined from this separation was 72% in agreement with the X-ray crystallinity of 74%. Changes of the crystalline NMR line shape were interperted in terms of oscillations around the chain axis, the r.m.s. oscillation amplitude varying from 5° at 40°C to 12° at 110°C. The central part of the NMR line shape indicates the existence of a “narrow” and a “medium” component…

Vacuum-ultraviolet absorption of hydrogenated and deuterated silanol groups and interstitial water molecules in amorphousSiO2

2005

Vacuum-ultraviolet (VUV) absorption cross sections of hydrogenated and deuterated silanol groups (SiOX, where $\mathrm{X}=\mathrm{H}$ or D) as well as interstitial water molecules $({\mathrm{X}}_{2}\mathrm{O})$ in amorphous $\mathrm{Si}{\mathrm{O}}_{2}$ $(a\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2})$ were determined between photon energies of 7 and $8.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The absorption bands for the deuterated species are blueshifted compared to those for the hydrogenated ones by $\ensuremath{\sim}0.1\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}0.2\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ as a result of a decrease in the zero-point energy associat…

Ni participation in the magnetism of Fe-Ni-Si-B amorphous alloys.

1987

$^{61}\mathrm{Ni}$ M\"ossbauer measurements at 4.2 K have been performed on (${\mathrm{Fe}}_{\mathrm{x}}$${\mathrm{Ni}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${)}_{77}$${\mathrm{Si}}_{1013}$ amorphous alloys with x=0.0, 0.1, and 0.9. Ni atoms in ${\mathrm{Ni}}_{77}$${\mathrm{Si}}_{10}$${\mathrm{B}}_{13}$ bear no magnetic moment, whereas in (${\mathrm{Fe}}_{0.1}$${\mathrm{Ni}}_{0.9}$${)}_{77}$${\mathrm{Si}}_{10}$${\mathrm{B}}_{13}$ and (${\mathrm{Fe}}_{0.9}$${\mathrm{Ni}}_{0.1}$${)}_{77}$${\mathrm{Si}}_{10}$${\mathrm{B}}_{13}$ their moments are, respectively 0.38${\ensuremath{\mu}}_{B}$ and 0.65${\ensuremath{\mu}}_{B}$. Our results, together with the literature data, show that Ni atoms in Fe-…

INFLUENCE OF THE ANODIZATION CONDITIONS ON THE ELECTRONIC PROPERTIES AND CRYSTALLOGRAPHIC STRUCTURES OF THE CORROSION LAYERS ON TUNGSTEN. A PHOTOELEC…

1983

ABSTRACT The influence of morphology, composition and crystallographic structure on the photoelectrochemical behaviour of anodic oxide films on tungsten obtained in various conditions of anodization has been investigated. Different photocurrent spectra and absorption edges were obtained for each type of film. Optical band gaps ranging between 2.55 eV and 3.15 eV were determined for crystalline and amorphous WO 3 films grown in different conditions. The low quantum efficiency of the anodic films must be attributed to the presence of an amorphous (a-W0 3 ) film which controls the transport of the injected photocarriers.

1986

The molecular order and mobility of two liquid-crystalline polyacrylates with phenyl benzoate moieties as mesogenic side groups and (CH2)m spacers (m = 2 and m = 6) were investigated by pulsed 2H NMR. The mesogenic side groups were isotopically labelled at the terminal phenylene ring. In the glassy state the orientational distribution function was characterized from the angular dependence of the 2H NMR line shape of samples macroscopically ordered in their nematic phase by the 8,4 T magnetic field of an NMR spectrometer. It was found to be Gaussian with widths of ± 18,5° and ± 10,5° for the m = 2 frozen nematic and m = 6 frozen smectic system, respectively. The phenylene rings undergo 180° …

Amorphous Ge15Te85: density functional, high-energy x-ray and neutron diffraction study

2011

The structure and electronic properties of amorphous Ge15Te85 have been studied by combining density functional (DF) simulations with high-energy x-ray and neutron diffraction measurements. Three models with 560 atoms have been constructed using reverse Monte Carlo methods constrained to (1) agree with the experimental structure factors S(Q), and have (2) energies close to the DF minimum and (3) a semiconducting band structure. The best structure is based on the melt-quenched DF structure and has a small number of Ge–Ge bonds. It shows interlocking networks of Te and GeTe with a significant fraction (22–24%) of voids (cavities). Ge occurs with both tetrahedral and 3 + 3 defective octahedral…

15N NMR studies of tautomerism

2012

The literature related to 15N NMR studies of tautomerism is updated and discussed. The 15N NMR data show that the technique is applicable for both liquid and solid state (both crystalline and amorphous) materials. Modern computational methods combined with experimental NMR data can aid in the chemical shift assignments especially in case of crystalline materials (so-called NMR crystallography). This review article is divided into chapters based on the different classes of compounds and a brief description of experimental and computational NMR techniques is also included.