共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of Physics and Chemistry of Solids》2007,68(5-6):701-706
Nitrogen-doped diamond-like carbon (DLC) layers (a-C:H:N, N-DLC or DLN) were prepared by the plasma-enhanced chemical vapor deposition (PECVD) technique, using a RF capacitive discharge (13.56 MHz), at low pressures (20 Pa), produced from a mixture of methane, nitrogen and hexamethyldisiloxane (HMDSO), deposited on single-crystalline silicon wafers placed on steel samples. The films, of differing deposition times, were subjected to laser ablation time-of-flight (LA-TOF) mass spectrometric measurements, using different commercial instrumentation to characterize their structures. The analysis of mass spectra was made and the following positively singly charged species were detected and identified: Cn+ (n=4–30), Sin+ (n=2, 3), SinH+ (n=2, 3), SiOK+, Si3H4+, Si2N+, Si2NH2+, and Si3C+. The later three species could reflect the presence of nitrogen–silica and carbon–silica chemical bonds in the structure of the DLN layer. The stoichiometry of all species was confirmed by isotopic pattern simulation. In the negative detection mode, the Cn− (n=2–12) clusters were observed. The findings are discussed in the light of the current research concerning analysis of the DLN thin layers and it is concluded that namely Si2N+, Si2NH2+ and Si3C+ species are reflecting the chemical structure of the DLN layer. LA-TOF-MS was found useful supplementary method for the characterization of DLN nano-layers. 相似文献
2.
W.-C. Tsai S.-K. Wang L.-C. Chou J. Chen Y.-H. Wu H.-C. Chen C.-R. Wen 《Surface science》2010,604(17-18):1494-1501
Continuous-time photoelectron spectroscopy (PES) and photon-exposure-dependent photon-stimulated desorption (PSD) were employed to investigate the monochromatic soft X-ray-induced dissociation of SF6 molecules adsorbed on Si(111)-7 × 7 at 30 K (SF6 dose = 3.4 × 1013 molecules/cm2, ~ 0.5 monolayer). The photon-induced evolution of adsorbed SF6 was monitored at photon energies of 98 and 120 eV [near the Si(2p) edge], and sequential valence-level PES spectra made it possible to deduce the photolysis cross section as a function of energy. It was found that the photolysis cross sections for 98 and 120 eV photons are ~ 2.7 × 10? 17 and ~ 3.7 × 10?17 cm2, respectively. The changes in the F? and F+ PSD ion yields were also measured during irradiation of 120 eV photons. The photon-exposure dependencies of the F? and F+ ion yields show the characteristics: (a) the dissociation of adsorbed SF6 molecules is ascribable to the substrate-mediated dissociations [dissociative attachment (DA) and dipolar dissociation (DD) induced by the photoelectrons emitting from the silicon substrate]; (b) at early stages of photolysis, the F? yield is mainly due to DA and DD of the adsorbed SF6 molecules, while at high photon exposure the F? formation by electron capture of the F+ ion is likely to be the dominant mechanism; (c) the F+ ion desorption is associated with the bond breaking of the surface SiF species; (d) the surface SiF is formed by reaction of the surface Si atom with the fluorine atom or F? ion produced by scission of S–F bond of SFn (n = 1–6) species. 相似文献
3.
The secondary ion mass spectrum of silicon sputtered by high energy C60+ ions in sputter equilibrium is found to be dominated by Si clusters and we report the relative yields of Sim+ (1 ≤ m ≤ 15) and various SimCn+ clusters (1 ≤ m ≤ 11 for n = 1; 1 ≤ m ≤ 6 for n = 2; 1 ≤ m ≤ 4 for n = 3). The yields of Sim+ clusters up to Si7+ are significant (between 0.1 and 0.6 of the Si+ yield) with even numbered clusters Si4+ and Si6+ having the highest probability of formation. The abundances of cluster ions between Si8+ and Si11+ are still significant (>1% relative to Si+) but drop by a factor of ∼100 between Si11+ and Si13+. The probability of formation of clusters Si13+-Si15+ is approximately constant at ∼5 × 10−4 relative to Si+ and rising a little for Si15+, but clusters beyond Si15 are not detected (Sim≥16+/Si+ < 1 × 10−4). The probability of formation of Sim+ and SimCn+ clusters depends only very weakly on the C60+ primary ion energy between 13.5 keV and 37.5 keV. The behaviour of Sim+ and SimCn+ cluster ions was also investigated for impacts onto a fresh Si surface to study the effects that saturation of the surface with C60+ in reaching sputter equilibrium may have had on the measured abundances. By comparison, there are very minor amounts of pure Sim+ clusters produced during C60+ sputtering of silica (SiO2) and various silicate minerals. The abundances for clusters heavier than Si2+ are very small compared to the case where Si is the target.The data reported here suggest that Sim+ and SimCn+ cluster abundances may be consistent in a qualitative way with theoretical modelling by others which predicts each carbon atom to bind with 3-4 Si atoms in the sample. This experimental data may now be used to improve theoretical modelling. 相似文献
4.
《Solid State Ionics》2006,177(5-6):437-445
Structural and electronic properties of semiconductor binary microclusters AlnAsm− anions have been investigated using the B3LYP-DFT method in the ranges of n = 1,2 and m = 1–7. Full structural optimization, adiabatic electron affinities calculation and frequency analysis are performed with the basis of 6–311 + G(d). The charged-induced structural changes in these anions have been discussed. The strong As–As bond is also favored over Al–As bonds in the AlnAsm− anions in comparison with corresponding neutral cluster. Among different AlAsm− and Al2Asm− (m = 1–7) anions, AlAs4− and Al2As3− are most stable. 相似文献
5.
Shin-ya Ohno Kei Inoue Masahiro Morimoto Sadanori Arae Hiroaki Toyoshima Akitaka Yoshigoe Yuden Teraoka Shoichi Ogata Tetsuji Yasuda Masatoshi Tanaka 《Surface science》2012,606(21-22):1685-1692
The initial oxidation on high-index silicon surfaces with (113) and (120) orientations at 820 K has been investigated by real-time X-ray photoemission spectroscopy (Si 2p and O 1s) using 687 eV photons. The time evolutions of the Sin+ (n = 1–4) components in the Si 2p spectrum indicate that the Si2 + state is suppressed on high-index surfaces compared with Si(001). The O 1s state consists of two components, a low-binding-energy component (LBC) and a high-binding-energy component (HBC). It is suggested that the O atom in strained SiOSi contributes to the LBC component. The reaction rates are slower on high-index surfaces compared with that on Si(001). 相似文献
6.
A.M. Kokhkharov S.A. Bakhramov U.K. Makhmanov R.A. Kokhkharov E.A. Zakhidov 《Optics Communications》2012,285(12):2947-2951
Nonlinear self-rotation of elliptically polarized laser pulses (λ = 532 nm, τFWHM ~ 12 ns) in toluene, benzene and binary mixture (toluene + ethanol) solutions of fullerene C70 has been investigated experimentally. Absolute values and signs of the nonlinear refractive indices (n2) and nonlinear optical susceptibilities χ(3)(ω, ? ω, ω) of C70 solutions in toluene and benzene at different values of polarization ellipse (θ = 0.2 ÷ 0.8) have been determined. High-resolution transmission electron microscope studies of C70 solutions showed that in toluene + ethanol mixtures ball-shaped C70 clusters are formed with particle sizes in the range ~ 100 ÷ 500 nm. It has been demonstrated, that the clusters sizes depend on the C70 concentration and volume fraction of ethanol in toluene. Correlation between the processes of C70 clusters formation in solutions and the values of polarization self-rotation angle of transmitted laser beam has been demonstrated. Physical mechanisms of laser induced optical activity in fullerene solutions have been discussed. 相似文献
7.
Yang Xia Bangwu Liu Sihua Zhong Chaobo Li 《Journal of Electron Spectroscopy and Related Phenomena》2012,184(11-12):589-592
The black silicon has been produced by plasma immersion ion implantation (PIII) process. The microstructure and optical reflectance are characterized by field emission scanning electron microscope and spectrophotometer. Results show that the black silicon appears porous or needle-like microstructure with the average reflectance of 4.87% and 2.12%, respectively. The surface state is investigated by X-ray photoelectron spectroscopy (XPS) technique. The surface of the black silicon is composed of silicon, carbon, oxygen and fluorine element. The formation of SixOyFz in the surface of black silicon can be proved clearly by the O 1s, F 1s and Si 2p XPS spectra. The formation mechanism of the black silicon produced by PIII process can be obtained from XPS results. The porous or needle-like structure of the black silicon will be formed under the competition of SFx+ (x ≤ 5) and F+ ions etching effect, SixOyFz passivation and ion bombardment. 相似文献
8.
The kinetics of the C6H5 reactions with CH3OH and C2H5OH has been measured by pulsed-laser photolysis/mass-spectrometry (PLP/MS) employing acetophenone as the radical source. Kinetic modeling of the benzene formed in the reactions over the temperature range 306–771 K allows us to reliably determine the total rate constants for H-abstraction reactions. In order to improve our low temperature measurements down to 304 K we have also applied the cavity ring-down spectrometric technique using nitrosobenzene as the radical source. Both sets of data agree closely. A weighted least-squares analysis of the two complementary sets of data for the two reactions gave the total rate constants k(CH3OH) = (7.82 ± 0.44) × 1011 exp [?(853 ± 30)/T] and k(C2H5OH) = (5.73 ± 0.58) × 1011 exp [?(1103 ± 44)/T] cm3 mol?1 s?1 for the temperature range studied. Theoretically, four possible product channels of the C6H5 + CH3OH reaction producing C6H6 + CH3O, C6H6 + CH2OH, C6H5OH + CH3 and C6H5OCH3 + H and five possible product channels of the C6H5 + C2H5OH reaction producing C6H6 + C2H5O, C6H6 + CH2CH2OH, C6H6 + CH3CHOH, C6H5OH + CH3CH2 and C6H5OCH2CH3 + H have been computed at the G2M//B3LYP/6?311+G(d, p) level of theory. The hydrogen abstraction channels were predicted to have lower energy barriers than those for the substitution reactions and their rate constants were calculated by the microcanonical variational transition state theory at 200–3000 K. The predicted rate constants are in good agreement with the experimental values. Significantly, the rate constant for the CH3OH reaction with C6H5 was found to be greater than that for the C2H5OH reaction and both reactions were found computationally to be dominated by H-abstraction from the hydroxyl group attributable to the affinity of the phenyl toward the OH group and the predicted lower energy barriers for the OH attack. 相似文献
9.
《Journal of Electron Spectroscopy and Related Phenomena》2005,142(2):91-96
The spectra of the Ba 6pnk autoionizing Stark states with |M| = 0, 1, converging to the 6p1/2+ and 6p3/2+ ionization thresholds, are measured as a function of the electric field strength F. Several 6pjnk Stark manifolds with n = 13–15 have been systematically studied in order to explore their characteristics of configuration interaction. Experimental results are analyzed by fitting them to the Lorentzian profile, from which the positions and widths are determined. Different spectroscopic properties between the Ba 6p1/2nk and 6p3/2nk autoionizing Stark states are investigated. Comparison between the Ba 6pjnk autoionizing Stark states with |M| = 0 and those with |M| = 1 are made. 相似文献
10.
Kwang-Sei Lee Jin Jung Kweon In-Hwan Oh Cheol Eui Lee 《Journal of Physics and Chemistry of Solids》2012,73(7):890-895
Phase transformations in squaric acid (H2C4O4) have been investigated by thermogravimetry and differential scanning calorimetry with different heating rates β. The mass loss in TG apparently begins at onset temperatures Tdi=245±5 °C (β=5 °C min?1), 262±5 °C (β=10 °C min?1), and 275±5 °C (β=20 °C min?1). A polymorphic phase transition was recognized as a weak endothermic peak in DSC around 101 °C (Tc+). Further heating with β=10 °C min?1 in DSC revealed deviation of the baseline around 310 °C (Ti), and a large unusual exothermic peak around 355 °C (Tp), which are interpreted as an onset and a peak temperature of thermal decomposition, respectively. The activation energy of the thermal decomposition was obtained by employing relevant models. Thermal decomposition was recognized as a carbonization process, resulting in amorphous carbon. 相似文献
11.
Theoretical calculations focused on the geometry, stability, electronic and magnetic properties of small palladium clusters Pdn (n=1–5) adsorbed on the NiAl(1 1 0) alloy surface were carried out within the framework of density functional theory (DFT). In agreement with the experimental observations, both Ni-bridge and Al-bridge sites are preferential for the adsorption of single palladium atom, with an adsorption energy difference of 0.04 eV. Among the possible structures considered for Pdn (n=1–5) clusters adsorbed on NiAl(1 1 0) surface, Pd atoms tend to form one-dimensional (1D) chain structure at low coverage (from Pd1 to Pd3) and two-dimensional (2D) structures are more stable than three-dimensional (3D) structures for Pd4 and Pd5. Furthermore, metal-substrate bonding prevails over metal–metal bonding for Pd cluster adsorbed on NiAl(1 1 0) surface. The density of states for Pd atoms of Pd/NiAl(1 1 0) system are strongly affected by their chemical environment. The magnetic feature emerged upon the adsorption of Pd clusters on NiAl(1 1 0) surface was due to the charge transfer between Pd atoms and the substrate. These findings may shade light on the understanding of the growth of Pd metal clusters on alloy surface and the construction of nanoscale devices. 相似文献
12.
P. Mélinon F. Tournus B. Masenelli A. Perez M. Pellarin J. Lermé M. Broyer B. Champagnon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):337-340
This paper deals with a new type of SiC bonding where silicon atom seems to bridge C60 molecules. We have studied films obtained by deposition of (C60)nSim clusters prepared in a laser vaporization source. Prior deposition, free ionized clusters were studied in a time-of-flight
mass spectrometer. Mixed clusters (C60)nSim were clearly observed. Abundance and photofragmentation mass spectroscopies revealed the relatively high stability of the
(C60)nSi
n
+
, (C60)nSi
n - 1
+
and (C60)nSi
n - 2
+
species. This observation is in favor of the arrangement of these complexes as polymers where the C60 cages may be bridged by a silicon atom. Free neutral clusters are then deposited onto substrate making up a nanogranular
thin film (≃ 100 nm). The film is probed by Auger and X-ray photoemission spectroscopies, but above all by surface enhanced Raman scattering.
The results suggest an unusual chemical bonding between silicon and carbon and the environment of the silicon atom is expected
to be totally different from the sp3 lattice: ten or twelve carbon neighbors might surround silicon atom. The bonding is discussed to the light of the so-called
fullerene polymerization as observed for pure fullerite upon laser irradiation. This opens a new route for bridging C60 molecules together with an appreciable energy bonding, since the usual van der Waals bonding in fullerite could be replaced
by an ionocovalent bond. Such an assumption must be checked in the future by XAS and EXAFS experiments.
Received 15 November 2000 相似文献
13.
The dielectric and pyroelectric responses of MgO-modified Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ceramics were investigated near FR(LT)–FR(HT) phase transition. It was found that MgO additive reduced the FR(LT)–FR(HT) phase transition temperature from 41 °C to room temperature (24 °C). Superior room-temperature pyroelectric properties were obtained in the composition of 0.10 wt% MgO addition without DC bias. The largest pyroelectric coefficient, 65 × 10−8 C cm−2 K−1, was detected. Accordingly, the detectivity figures of merit Fd had maximum values of 20 × 10−5 Pa−1/2, and especially the voltage responsivity Fv = 0.91 m2C−1 is the highest value reported so far among all pyroelectric materials. It shows promising potential for application in uncooled pyroelectric infrared detector. 相似文献
14.
《Solid State Ionics》2006,177(3-4):323-331
The fundamental electrochemical properties of lithium perfluoroalkyltrifluoroborates Li[CnF2n+1BF3] (n = 1∼4) were evaluated as electrolyte salts for lithium-ion battery in comparison with LiBF4 and LiPF6. Li[CnF2n+1BF3] showed higher electrolytic conductivities than LiBF4 in aprotic solvents. In these series, the conductivities decreased with the perfluoroalkyl group being longer, and Li[C2F5BF3] exhibited a comparable conductivity to LiPF6. The relationship between the conductivity and the anion size showed that the anion with a moderate size is in favor of obtaining high conductivities. The limiting oxidation potentials determined by linear sweep voltammetry demonstrated that Li[CnF2n+1BF3] were less resistant against oxidation than LiBF4. The HOMO energies and ionization energies of [CnF2n+1BF3]− calculated by ab initio molecular orbital (MO) theory and density functional theory (DFT) supported this observation, however, there was no accuracy to explain the effect of the chain length of perfluoroalkyl groups on the limiting oxidation potentials. The cell performances of a LiC6/Li0.5CoO2 cell using Li[C2F5BF3] were comparable to those using LiPF6 at room temperature, however, it deteriorated at elevated temperature due to the reaction on the cathode. 相似文献
15.
N. Ding J. Xu Y.X. Yao G. Wegner X. Fang C.H. Chen I. Lieberwirth 《Solid State Ionics》2009,180(2-3):222-225
The diffusion coefficients of lithium ions (DLi+) in nano-Si were determined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). DLi+ values are estimated to be ~ 10? 12 cm2 s? 1 and exhibit a “W” type varying with the lithium concentration in silicon. Two minimum regions of DLi+ (at Li2.1 ± 0.2Si and Li3.2 ± 0.2Si) are found, which probably result from two amorphous compositions (a-Li7Si3 and a-Li13Si4). Besides the two minimum regions, one maximum DLi+ is observed at Li15Si4, corresponding to the crystallization of highly lithiated amorphous LixSi. 相似文献
16.
The title compound C6H5CH2C5H4NH+·HSeO4− crystallizes in the orthorhombic system with the space group Pbca and the following unit cell dimensions: a=27.449(5) Å; b=10.821(6) Å and c=8.830(1) Å.The structure consists of infinite parallel two-dimensional planes built of HSeO4− anions and C6H5CH2C5H4NH+ cations mutually.Differential scanning calorimetry study on 4-benzylpyridinium monohydrogen-selenate was carried out. A high temperature second order phase transition at 363 K was found and characterized by electric measurements. The Raman of polycrystalline sample has been recorded at different temperature between 297 and 373 K.The conductivity relaxation parameters associated with some H+ conduction have been determined from an analysis of the M′′/M′′max spectrum measured in a wide temperature range. An appearance of the superionic phase transition in 4-BSe is closely related to a liberation or even a rotation increase of HSeO4− groups with heating. 相似文献
17.
Y. Boyarintseva N. Shiran A. Gektin V. Nesterkina K. Shimamura E. Villora 《Radiation measurements》2010,45(3-6):340-342
The radiation stability of the mixed crystals M1 ? xRxF2 + x (M = Ca, Sr, Ba) depends on types of the alkaline-earth and rare-earth ions. Different to Eu- and Ce-containing systems, M1 ? xPrxF2 + x solid solutions have a low radiation resistance, which may be associated with hole trapping on praseodymium ion according to the reaction Pr3+ → Pr4+ which is typical for praseodymium. The coloration efficiency of M1 ? xPrxF2 + x crystals grows in the row Ca → Sr → Ba, which is explained satisfactorily within the model of rare-earth clusters, the structure of which is determined by the ratio of the base alkaline-earth cation to the praseodymium ion radii. 相似文献
18.
Tian Chen Chao Ye Yanhong Deng Ying Yuan Shuibin Ge Yijun Xu Zhaoyuan Ning Xiaopin Pan Zhenmin Wang 《Journal of luminescence》2012,132(9):2416-2420
Amorphous Si:C:O:H films were fabricated at low temperature by C2F6 and O2/C2F6 plasma treating silicone oil liquid. The a-Si:C:O:H films fabricated by C2F6 plasma treatment exhibited white photoluminescence at room temperature, while that by O2/C2F6 plasma treatment exhibited blue photoluminescence. Fourier transformed infrared spectroscopy and Raman spectroscopy studies showed that the sp3 and sp2 hybridized carbons, SiC bond, SiO bond and carbon-related defects in a-Si:C:O:H films correlated with photoluminescence. It is suggested that the blue emission at 469 nm was related to the sp3 and sp2 hybridized carbons, SiC bond, carbon dangling bonds as well as SiO short chains and small clusters, while the light emitting at 554 nm was related to the carbon-related defects. 相似文献
19.
Density functional theory (DFT) calculations are performed to investigate the electronic features of the structures of fluorinated polysilanes SinFn (n=4, 6, 8, 10, 12, 20, 24, 28, 30, 32, 36, 50, and 60). Among all of these fluorinated polysilanes, Si20F20 has the highest binding energy and, thus, stability. The binding energy then shows a very slow (monotonically) decrease as the size of the fluorinated silicon fullerene n≥20 increases which can be related to an increase in fluorine–fluorine repulsion. Following an irregular pattern, the HOMO–LUMO energy gap strongly depends on the size of the cage. On the other hand, 29Si CS parameters detect equivalent electronic environment for silicon atoms within SinHn polysilanes with n≤20 while 29Si NMR pattern indicates a few separated peaks for SinHn polysilanes with n≥20. Seeking correlation between these peaks and local structures around silicon sites, Siα, Siβ, Siγ observed in these models shows that δiso(Siγ)<δiso(Siβ) <δiso(Siα). Obtaining similar values (458.8–478.7 ppm) of 19F calculated chemical shieldings for all the fluorinated polysilanes means the same tendency of the silicon atoms on the surfaces of all cages for contribution to chemical bonding with fluorine atoms. 相似文献
20.
The influence of the underlying interface on adsorption of cobalt (Co) is investigated by comparing the nucleation and growth of Co at room temperature on three carbon (C) surfaces, i.e. highly oriented pyrolytic graphite (HOPG), epitaxial graphene/SiC(0001) (hereafter abbreviated as EG) and precursor of EG i.e. C-rich (6√3 × 6√3)R30°/SiC(0001) (hereafter abbreviated as 6√3). On all three surfaces, Co adopts Volmer–Weber growth mode via formation of three-dimensional dome-shaped nanoclusters. Co clusters formed on 6√3 surface are smaller but denser than Co/HOPG or Co/EG. Scaling analysis reveals a critical nucleus size, i* = 1 (atom) and the smallest stable cluster (i* + 1) would be a dimer. Co/HOPG and Co/EG have the same order of magnitude for their cluster densities and sizes. Scaling analyses however show that the i* for Co/EG (i* = 3) is larger than Co/HOPG (i* = 0) and in this respect the smallest stable cluster would be tetramer and monomer respectively. This difference is attributed to the influence of an interface situated between graphene and SiC bulk. It appears that EG is more inert than HOPG towards the adsorption of Co and may act as a better substrate to host Co clusters. 相似文献