Bonding Configurations (bonding + configuration)

Distribution by Scientific Domains
Polymers and Materials Science40%

Selected Abstracts

A new luminescent defect state in low temperature grown amorphous SiNxOy thin films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
Hengping Dong
Abstract We reported the observation of photoluminescence (PL) from low-temperature grown amorphous silicon oxynitride (a-SiNxOy) films with its peak location tunable in a wide range from 450 to 600 nm by controlling the Si/N ratios. The origin of luminescence from a-SiNxOy film has been thoroughly investigated. From the results of the optical absorbance spectrum, an oxygen-induced new luminescent defect state, which was characterized to be responsible for the light emission, was determined to locate at about 0.65 eV from the absorption edge. The measurements of Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectrum (XPS) has verified the existence of O-Si-N bonding configuration, which serves as this new luminescent defect state in this kind of material (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Imaging and Spectroscopy of Multiwalled Carbon Nanotubes during Oxidation: Defects and Oxygen Bonding (Adv. Mater.

ADVANCED MATERIALS, Issue 19 2009
19/2009)
Photoelectron spectromicroscopy studies revealed the morphology changes and the abundance of various oxygenated functional groups on individual multiwalled carbon nanotubes exposed to oxidizing environments. Alexei Barinov and co-workers show on page 1916 that carbonyl type bonding configurations prevail when fragmentation and extinction of the nanotubes occur. [source]

Electronic Structure and Bonding of All Crystalline Phases in the Silica,Yttria,Silicon Nitride Phase Equilibrium Diagram

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004
Wai-Yim Ching
This paper reviews the structures and properties of 10 binary, ternary, and quaternary crystals within the equilibrium phase diagram of the SiO2,Y2O3,Si3N4 system. They are binary compounds SiO2, Y2O3, Si3N4; ternary compounds Si2N2O, Y2Si2O7, and YSi2O5; and quaternary crystals Y2Si3N4O3 (M-melilite), Y4Si2O7N2, (N-YAM), YSiO2N (wallastonite), and Y10(SiO4)6N2 (N-apatite, N-APT). Although the binary compounds are well-known and extensively studied, the ternary and the quaternary crystals are not. Most of the ternary and the quaternary crystals simply have been referenced as secondary phases in the processing of nitrogen ceramics. Their crystal structures are complex and not precisely determined. In the quaternary crystals, there exists O/N disorder in that the exact atomic positions of the anions cannot be uniquely determined. It is envisioned that a variety of cation,anion bonding configurations exist in these complex crystals. The electronic structure and bonding in these crystals are, therefore, of great interest and are indispensable for a fundamental understanding of structural ceramics. We have used ab initio methods to study the structure and bonding properties of these 10 crystals. For crystals with unknown or incomplete structural information, we use an accurate total energy relaxation scheme to obtain the most likely atomic positions. Based on the theoretically modeled structures, the electronic structure and bonding in these crystals are investigated and related to various local cation,anion bonding configurations. These results are presented in the form of atom-resolved partial density of states, Mulliken effective charges, and bond order values. It is shown that Y,O and Y,N bonding are not negligible and should be a part of the discussion of the overall bonding schemes in these crystals. Spectroscopic properties in the form of complex, frequency-dependent dielectric functions, X-ray absorption near-edge structure (XANES), and the electron energy-loss near-edge structure (ELNES) spectra in these crystals also are calculated and compared. These results are discussed in the context of specific bonding configurations between cations (silicon and yttrium) and anions (oxygen and nitrogen) and their implications on intergranular thin films in polycrystalline Si3N4 containing rare-earth elements. [source]

Investigation of structural properties of high-rate deposited SiNx films prepared at low temperatures (100,300 °C) by atmospheric-pressure plasma CVD

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
Y. Yamaguchi
Abstract We have investigated the structural properties of silicon nitride (SiNx) films deposited at low temperatures (100,300 °C with very high rates (>50 nm/s) in atmospheric-pressure He/H2/SiH4/NH3 plasma excited by a 150 MHz very high-frequency (VHF) power using a cylindrical rotary electrode. For this purpose, SiNx films are prepared on Si(001) wafers varying NH3/SiH4 ratio, H2 concentration in the plasma and substrate temperature (Tsub). Infrared absorption spectroscopy is used to analyze the bonding configurations of Si, N and H atoms in the films. It is shown that by decreasing NH3/SiH4 ratio or increasing H2 concentration, Si,N and Si,H bond densities increase, while N,H bond density decreases. A reasonably good-quality film showing a BHF etching rate of 28 nm/min and a refractive index of 1.81 is obtained at Tsub = 300 °C despite the very high deposition rate of 166 nm/s. However, it is found that the decrease in Tsub causes the deterioration of film quality. Further surface excitation by increasing VHF power and/or H2 concentration together with the optimization of other deposition parameters will be needed to form high-quality SiNx films with high rates at lower temperatures (Tsub , 100 °C). (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Role of surface in light induced degradation of porous silicon

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007
N. P. Mandal
Abstract Exposure of porous silicon (PS) to moisture is found to increase its photoluminescence (PL) intensity, whereas it decreases drastically upon light soaking. On the other hand, coating by a thin layer of polystyrene protects PS against light induced degradation without changing PL significantly. Further, polystyrene coating protects the PS from humidity also. FTIR shows appearance of new bonding configurations at the PS/polymer interface, whcih may account for the improved stability. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]