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1.
Yasser B. Saddeek 《Journal of Non》2011,357(15):2920-2925
Ultrasonic studies on x B2O325 Li2O(75 − x) Bi2O3, (0 ≤ x ≤ 75 mol%) glasses have been carried out. The elastic moduli of glasses have been investigated using ultrasonic velocity measurements at 4 MHz. The results revealed an increase of the ultrasonic velocity and Debye temperature with the increase of the B2O3 content which was attributed to the increase in the packing density, the local contraction of the network around the Bi and Li cations and the increase of the number of bonds per unit volume. Also, the increase of the elastic moduli with the increase in the B2O3 content is affected with the increase in the dissociation energy, the average cross-link density, the increase in the number of bridging oxygen atoms, and the substitution of high bond strength BO with low bond strength BiO. The optical properties such as the refractive index, the energy gap and the optical polarizability were evaluated from the values of the elastic moduli. It was observed that as the bulk modulus increases, the optical energy gap increases and both the refractive index and the optical basicity decrease. 相似文献
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Fourier Transform Infrared (FTIR) Spectroscopy has long been utilized as an analytical technique for qualitatively determining the presence of various different chemical bonds in gasses, liquids, solids, and on surfaces. Most recently, FTIR has been proven to be extremely useful for understanding the different types of bonding present in low dielectric constant “low-k” organosilicate materials. These low-k materials are predominantly utilized in the nanoelectronics industry as the interlayer dielectric material in advanced Cu interconnect structures. In this article, we utilize FTIR to perform a detailed analysis of the changes in chemical bonding that occur in Plasma Enhanced Chemically Vapor Deposited (PECVD) low-k a-SiC:H thin films. PECVD low-k a-SiC:H materials are equally important in advanced Cu interconnects and are utilized as both etch stop and Cu diffusion barrier layers. We specifically investigate the changes that occur in low-k a-SiC:H films as the dielectric constant and mass density of these films are decreased from > 7 to < 3 and from 2.5 to 1 g/cm3 respectively. We show that decreases in mass density and dielectric constant are accompanied by both an increase in terminal SiHx and CHx bonding and a decrease in SiC network bonding. At densities of 1.85 g/cm3, the concentration of terminal SiHx bonding peaks and subsequent hydrogen incorporation are achieved predominantly via terminal CH3 groups. Low-k a-SiC:H films with k < 3.5 and density < 1.3 g/cm3 can be achieved via incorporating larger organic phenyl groups but result in non-stoichiometric carbon rich films. Electron beam curing of these lower density a-SiC:H films results in volatilization of the phenyl groups leaving behind nanoporous regions and production of some CCC chain linkages in the network. 相似文献
3.
Silicon based deposits were prepared by TEA CO2 pulsed laser ablation (PLA) of SiO and SiO2 targets in the atmosphere of selected gases (N2, He, Ne, Ar, Kr). These deposits possess high specific area of several hundreds m2 per gram. Owing to the high specific area, some chemical groups and hydrogen related radical were detected by means of FTIR and EPR analyses and theoretical calculations: silyl (E′ center) Si, silylen Si:, silanon SiO, POL (peroxy linkage) SiOOSi and/or NBOHC (non-bridging oxygen hole center) SiO, POR (peroxy radical) SiOO and dioxysilirane Si(O)2. In SiO2 deposits the concentration of silyl Si resp. POR SiOO was determined to be 5.8 × 1018/g resp. 6.2 × 1019/g. In SiO deposits the ratio [Si:]:[Si] = (3.1-5.7) × 1019/g: (5.3-9.8) × 1019/g was measured. Estimated concentration of [Si] in deposits was increased nearly five times in comparison with SiO target. After exposure of the SiO deposits to H2 EPR doublet with hyperfine splitting of 7.7 mT was observed. The best agreement between calculated theoretical and experimental values was found for the model [(HO)3SiO]2HSi. FTIR measurements and calculations of the silanol theoretical model clusters enabled us to discuss the chemical surroundings of the silanol and to determine the defects in the deposits. 相似文献
4.
The local atomic and electronic structures of equiatomic liquid alloy KSb have been investigated using ab initio molecular dynamics simulations. There is a small peak located at about 62° in the covalent SbSb bond-angle distribution function. The height of 62° peak increases with temperature. The further analysis show that this peak attributes to the triangular structures with each Sb atom covalently bonded to the other two in the liquid KSb and their number increases with temperature. Therefore, there exist isolated Sb atoms, covalently bonded Sb dimers, triangles with three covalent SbSb bonds and short covalently bonded Sb chains in the liquid KSb. Upon temperature increasing the covalent Sb chains tend to break into short pieces so that the isolated Sb atoms, covalently bonded Sb dimers and triangles with three covalent SbSb bonds increase in numbers. The obtained total electronic densities of states at different temperatures give a reasonable explanation of the electronic conductivity increasing with temperature. 相似文献
5.
V.S. Waman M.R. Pramod A.M. Funde D.P. Amalnerkar S.W. Gosavi 《Journal of Non》2011,357(21):3616-3622
Hydrogenated nanocrystalline silicon (nc-Si:H) films were prepared at high deposition rates (> 13 Å/s) from pure silane without hydrogen dilution by hot wire deposition method by varying filament-to-substrate distance (ds-f). In this study we have systematically and carefully investigated the effect of filament-to-substrate distance on structural, optical and electrical properties of the Si:H films. A variety of characterization techniques, including Raman spectroscopy, low angle X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM), UV-Visible-NIR spectroscopy and electrical dark and photoconductivity measurement were used to characterize these films. Films deposited at ds-f > 5 cm are amorphous while those deposited at ds-f < 5 cm are biphasic; a crystalline phase and an amorphous phase with nano-sized crystallites embedded in it. Low angle X-ray diffraction analysis showed that the crystallites in the films have preferential orientation along (111) directions. Decrease in ds-f, the crystallinity and crystalline size increases whereas hydrogen bonding shifts from mono-hydride (SiH) to di-hydride (SiH2) and poly-hydride (SiH2)n complexes. The band gaps of nc-Si:H films (~ 1.9-2.0 eV) are high compared to the a-Si:H films, while hydrogen content remains < 10 at.%. We attribute the high band gap to the quantum size effect. A correlation between electrical and structural properties has been established. Finally, from the present study it has been concluded that the filament-to-substrate distance is a key process parameter to induce the crystallinity in the films by hot wire method. The ease of depositing films with variable crystallite size and its volume fraction, and tunable band gap is useful for fabrication of tandem/micro-morph solar cells. 相似文献
6.
The structures of xCuO · (1 − x)P2O5 glasses (0 ? x ? 0.50) prepared in vacuum sealed silica ampoules were investigated using vibrational spectroscopies. With the addition of CuO, both infrared and Raman spectra indicate a systematic transformation from a three-dimensional ultraphosphate network dominated by Q3 tetrahedra into a chain-like metaphosphate structure dominated by Q2 tetrahedra. IR spectra clearly show two distinct Q3 sites with bands at 1378 and 1306 cm−1, assigned to PO bonds on isolated Q3 tetrahedra and PO bonds on tetrahedra that participate in the coordination environments of the Cu-octahedra, respectively. As CuO content increases, the intensity of the PO band associated with the tetrahedra increases to a maximum x ∼ 0.33, then decreases with a concomitant increase of the intensity of the band at 1265 cm−1, due to the asymmetric vibration of the PO2 groups on Q2 tetrahedra. When x > 0.33 the isolated Cu-octahedra begin to share common oxygens to form a sub-network in the phosphate matrix. The effects of glass structure on the glass properties, including density, refractive index, and glass transition temperature, are discussed. 相似文献
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Amorphous carbon nitride (CNx) films with silicon addition up to 16 at.% are sputter deposited on Si(1 0 0) substrate, and the surface morphology is studied with scaling method based on atomic force microscopy. The surface roughness σ, the roughness exponent α, and the lateral correlation length ξ decrease with silicon content of the films, reaching 0.33 nm, 0.80 and 50 nm, respectively, for the film with [Si] = 16 at.%. The addition of silicon in the films leads to additional Si-N, Si-C-N and CN bonds revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The films undergo a structural transition from columnar to smooth morphology in cross-section with silicon addition demonstrated by field emission scanning electron microscopy. Nano-sized clusters sparsely dispersed in amorphous matrix of the film with [Si] = 16 at.% are observed by high-resolution transmission microscopy. According to the surface growth mechanism in which surface diffusion and geometrical shadowing drive structural and morphological evolution of the sputter deposited films, surface smoothing of the amorphous CNx films by silicon addition is explained by the formation of Si-N and Si-C-N bonds that impede surface diffusion of the adsorbed species during film growth, which leads to the reduced size of the columnar structures. 相似文献
9.
Consolidation mechanism of materials obtained from sodium silicate solution and silica-based aggregates 总被引:1,自引:0,他引:1
Séka Simplice Kouassi 《Journal of Non》2011,357(15):3013-3021
A study based on the use of sodium silicate gels as binder for cold consolidation of silica-based aggregates has been investigated. The gels used as precursor of binder were synthesized by adding hydrochloric acid to a concentrated sodium silicate solution. Consolidated materials were obtained by mixing the previous solution before gelation with granular materials (fine silica powder and sand). The study of the gel-silica-sand ternary system shows that the existence domain of materials depends on the sand size distribution. The microstructure of gel-silica-sand ternary samples reveals the presence of the three components with a partial attack of grain surface. This was confirmed by FTIR experiments during the monitoring of the synthesis. Actually, the νasSiOSi broad band resulting from the average of the contribution of the set of Q4, Q3 and Q2 units with a sharp peak located around 1078 cm− 1, firstly shifts to lower wavenumber until 21 days and then to higher wavenumber characteristic of dissolution/precipitation reactions. On the other hand, the consolidation of the material is strong when the amount of fine silica in the material is high leading to efficient mechanical properties. Therefore, consolidation could be explained by the dissolution of small particles of silica and their precipitation into the grain boundary of sand. 相似文献
10.
Spectrometric and ellipsometric studies of (1 − x)TiO2 · xLn2O3 (Ln = Nd, Sm, Gd, Er, Yb) thin films
Spectrometric and ellipsometric studies of (1 − x)TiO2 · xLn2O3 (Ln = Nd, Sm, Gd, Er, Yb; x = 0.33, 0.5) thin films at room temperature were performed. The obtained dispersion dependences of refractive indices are successfully described by the optical-refractometric relation. The dependence of optical pseudogap and refractive indices on composition and molar mass of the films is investigated. The influence of compositional disordering on the energy width of the exponential absorption edge is studied. 相似文献
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Combined in-situ SAXS/WAXS and HRTEM study on crystallization of (Cu60Co40)1 − xZrx metallic glasses
CuZr as well as CoZr are well known metallic glass-formers in a wide compositional range. Since the binary Cu-Co system exhibits a metastable liquid-liquid miscibility gap, i.e. Cu and Co tend to separate from each other, the ternary Cu-Co-Zr system is a promising candidate to form phase separated glass-glass composites. In this work (Cu60Co40)1 − xZrx metallic glasses with relatively low Zr contents of x = 37 and x = 32 were prepared by melt spinning and investigated by in-situ small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Certain heat treated samples were additionally investigated by high-resolution transmission electron microscopy (HRTEM). Even for x = 32 there are no indications for any kind of phase separation in the as-quenched state within experimental resolution, i.e. the critical temperature Tc for a liquid-liquid phase separation has already decreased from 1556 K for binary Cu60Co40 to a temperature below the glass transition temperature Tg = 762(5)K found for (Cu60Co40)68Zr32. Combined in-situ SAXS/WAXS and HRTEM investigations reveal that thermal annealing also does not induce an amorphous-amorphous phase separation. Instead the formation of nano crystallites of a so far unknown Cu-rich/Zr-poor phase with relatively low activation energy for crystallization Ea = 116(7) kJ/mol at temperatures far below the crystallization temperature deduced from DSC measurements is observed. 相似文献
13.
P. Bharathan 《Journal of Non》2011,357(18):3366-3372
We have experimentally measured the current-voltage and capacitance-voltage characteristics of Au/amorphous AsxSe1 − x (x ≤ 0.05)/Zr trilayer structures at temperatures from 4 to 295 K. The observed capacitance of structures with an amorphous AsxSe1 − x (a-AsxSe1 − x) thickness of ~ 0.4 to ~ 2.8 μm does not significantly change over the entire range of applied bias (− 5 V to 5 V), indicating that the a-AsxSe1 − x films are fully depleted and thus the structures are Mott barriers. The current-voltage (I-V) characteristics of the a-As0.03Se0.97 device at low (< 3000 V/cm) to moderate fields (3000 V/cm-10000 V/cm) follow the predictions of trap limited space charge conduction theory, as they exhibit Ohmic behavior at low fields and trap limited space charge current at moderate fields. According to the trap limited space charge current model of Lampert, the a-As0.03Se0.97 film has an effective hole mobility, Θμ (with Θ < 1), of ~ 5 × 10− 7 cm2/V-sec at 295 K. This value is similar to, but consistently lower than previously reported mobilities inferred from time of flight measurements. The current at high fields (> 104 V/cm) increases rapidly with applied field as a result of carrier emission from localized states and is consistent with transport by the Poole-Frenkel mechanism. A permanent transition to a high conductance state (~ 10− 3 S) is observed after exposure to very high electric fields (~ 4 × 105V/cm). 相似文献
14.
It was discovered that E′ centers were created by heat-treatment when silica glass contains water and has residual stress. Silica glass samples were heat-treated at 1000 °C for various lengths of time in 355 torr (47 000 Pa) water vapor pressure and dry nitrogen gas atmospheres. The electron paramagnetic resonance (EPR) signal of E′ centers increased initially with heat-treatment time in both atmospheres but then decreased afterwards in the wet atmosphere. It is known that water molecules eliminate paramagnetic defects, such as E′ centers and non-bridging oxygen hole centers (NBOHCs) by reacting with these defects in the glass, transforming them to non-paramagnetic species such as Si-OH or Si-H. The present study indicates that water molecules are also capable of initially creating paramagnetic defects in the glass structure by breaking the silica network structure in the presence of stress. The present observation may be relevant to mechanical strength reduction of silica glasses, which is commonly observed in the presence of water and stress. 相似文献
15.
Archna Jaiswal 《Journal of Non》2004,344(3):135-147
Zero-field and in-field (at 8 T) conductivity vs temperature (σ-T), magneto-resistance (Δρ/ρ), magnetization vs temperature (M-T) and magnetization vs field (M-H) of unannealed Al70Pd20Mn10 and annealed Al70Pd20Mn10, Al70Pd21Mn9 and Al70Pd22Mn8 quasicrystalline alloys have been studied in the temperature range of 1.4-300 K. Room temperature resistivity and the low-temperature magneto-resistance show a correlation with the corresponding magnetization. The σ-T for all the studied samples shows a pair of minima and maxima. The σ-T maxima show a correlation with the total magnetization. The analysis shows that σ-T is dominated by weak-localization effects. The minima are arising due to competing inelastic scattering times τi (e-ph scattering in the dirty metallic limit, τi ∝ T−2) and the Kondo-type spin-flip scattering time τsf whereas the maxima has been attributed to ‘Kondo-maxima’, occurring due to maxima in the spin-flip rate . The magneto-resistance of these samples shows a changeover from negative to positive where the negative component shows a correlation with the magnetization of the sample. The values of parameters derived from refinement give spin-flip scattering fields, which are found to be correlated with the total sample magnetization. 相似文献
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C. Derbidge 《Journal of Non》2005,351(3):233-238
The photoluminescence and optical absorption spectra in glassy AsxSe1−x with 0.08 ? x ? 0.40 are essentially independent of x. The PL spectra peak at approximately half the optical gap and the exponential slopes of the optical absorption edges are all approximately 75 meV. For x > 0.4, the PL peaks shift to higher energies, the widths of the PL spectra increase, and there is a strong component to the optical absorption well below the optical gap. Comparisons with ESR experiments in the AsxS1−x system suggest the possibility of two PL peaks. The second PL peak and the optical absorption below the optical band gap for x > 0.4 are attributed to the presence of As-As bonds. 相似文献
19.
Cd1 − xFexTe single crystals were prepared by vapour phase growth method in the composition range of 0 ≤ x ≤ 0.03. Chemical analysis, surface morphology, structural investigations and electrical properties were carried out by EDAX, SEM, XRD, TEM and transport technique, respectively. Microscopic variations between the target and actual compositions were noticed. Morphology studies revealed that dislocation aided growth is active in the present crystals. TEM and XRD studies confirmed that the samples of all compositions crystallized in zinc blende structure, and the lattice parameters varied almost linearly decreases with Fe content. At room temperature, the resistivity of the Cd1 − xFexTe crystals of all compositions (x = 0.01, 0.015, 0.02, 0.025 and 0.03) lies in the range of 3.5-6.5 M Ω, the activation energies lie in the range of 63-133 meV, and the samples were show the ‘p’ type conductivity. 相似文献
20.
S.-Y. Seo C.-H. Kwak S.-H. Kim B.-H. Kim C.-I. Park S.-H. Park S.-W. Han 《Journal of Crystal Growth》2010,312(14):2093-2097
High quality Zn1−xFexO thin films were deposited on α-sapphire substrates by RF magnetron sputtering. X-ray absorption fine structure measurements showed that the chemical valence of Fe ions in the films was a mixture of 2+ and 3+ states, and Fe ions substituted mainly for the Zn sites in the films. DC-magnetization measurements revealed ferromagnetic properties from 5 to 300 K. The photoluminescence measurements at 15 K showed a sharp main transition peak at 3.35 eV along with a broad impurity peak at 2.45 eV. The structural and magnetization analyses of the Zn1−xFexO films strongly suggested that the ferromagnetism was the intrinsic properties of the films. 相似文献