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1.
Nickel containing amorphous carbon (a-C:Ni) films have been deposited by filtered cathodic vacuum arc (FCVA) technique by introducing pure nickel into the graphite target. The field electron emission property of a-C:Ni was improved when compared to that of pure tetrahedral amorphous carbon (ta-C) by FCVA. The emission threshold field of a-C:Ni film is about 5 V μm −1, whilst the threshold field of the ta-C film is about 13 V μm −1. Raman spectroscopy suggests that the sp 2 clusters in the carbon film increase both in size and number when Ni is introduced. However, the emission was found to degrade to threshold fields beyond 20 V μm −1 after the a-C:Ni film was left in ambient for a week. This observation is attributed to surface absorption of oxygen on the a-C:Ni film, as determined by X-ray Photoelectron Spectroscopy. 相似文献
2.
The carbon nitride (CN x) coating with its novel properties will be excellent candidate for biomedical applications. CN x coatings were prepared on the surface of Ti–6Al–4V by ion-beam-assisted deposition (IBAD) with different NH n+ beam bombarding energies at low substrate temperature. The coatings were characterized by Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. The result showed that the wear-resistance of CN x coatings was better at higher beam bombarding energy. The cell attachment tests also gave interesting results that CN x coatings exhibited low macrophage attachment and provide desirable surface for the normal cellular growth and morphology of the fibroblasts. Structural analysis showed that NH n+ beam bombardment at the energies of 300–400 eV could result in more nitrogen concentration and fraction of sp 3CN bonds in the structure of CN x coatings, which may be responsible for the improvement in the wear-resistance and the cell attachment. 相似文献
3.
The adsorption reactions and binding configurations of cyclohexene, 1,3-cyclohexadiene and 1,4-cyclohexadiene on Si(1 1 1)-7 × 7 were studied using high-resolution electron energy loss spectroscopy (HREELS), ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and DFT calculation. The covalent attachments of these unsaturated hydrocarbons to Si(1 1 1)-7 × 7 through the formation of Si–C linkages are clearly demonstrated by the observation of the Si–C stretching mode at 450–500 cm −1 in their HREELS spectra. For chemisorbed cyclohexene, the involvement of π C=C in binding is further supported by the absence of C=C stretching modes and the disappearance of the π C=C photoemission. The chemisorption of both 1,3-cyclohexadiene and 1,4-cyclohexadiene leads to the formation of cyclohexene-like intermediates through di-σ bonding. The existence of one π C=C bond in their chemisorbed states is confirmed by the observation of the C=C and (sp 2)C---H stretching modes and the UPS and XPS results. DFT calculations show that [4 + 2]-like cycloaddition is thermodynamically preferred for 1,3-cyclohexadiene on Si(1 1 1)-7 × 7, but a [2 + 2]-like reaction mechanism is proposed for the covalent attachment of cyclohexene and 1,4-cyclohexadiene. 相似文献
4.
Carbon nitride thin films were deposited on Si(1 0 0) substrate by microwave plasma-enhanced chemical vapor deposition (PECVD). Hexamethylenetetramine (HMTA) was used as carbon and nitrogen source while N 2 gas was used as both nitrogen source and carrier gas. The sp 3-bonded C---N structure in HMTA was considered significantly in the precursor selection. X-ray diffraction analysis indicated that the film was a mixture of crystalline - and β-C 3N 4 as well as graphitic-C 3N 4 and β-Si 3N 4 which were not easily distinguished. Raman spectroscopy also suggested the existence of - and β-C 3N 4 in the films. X-ray photoelectron spectroscopy study indicated the presence of sp 2- and sp 3-bonded C---N structures in the films while sp 3C---N bonding structure predominated to the sp 2 C---N bonding structure in the bulk composition of the films. N was also found to be bound to Si atoms in the films. The product was, therefore, described as CN x:Si, where x depends on the film depth, with some evidences of crystalline C 3N 4 formation. 相似文献
5.
This paper reports the effect of positive substrate bias ( Vs) varying from 0 to 180 V on the spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES) studies of diamond-like carbon (DLC) films deposited using CH 4 gas as a feedstock into a saddle field fast atom beam (FAB) source. The values of optical constants like refractive index ( n) and extinction coefficient ( k) of the deposited DLC films were determined using a two phase model. The values of ‘ n’ were found to fall in the range from 1.505 to 1.720 and ‘ k’ from 0.03 to 0.125 by application of different values of Vs. Value of these optical constants were found to decrease with the increase of substrate bias up to 90 V and then increase beyond this value. Position of C 1s peak evaluated from XPS data was found to occur at 286.09±0.18 eV in DLC films deposited by application of different values of Vs. Observation of full width at half maximum (FWHM) ( τ) value (1.928 eV at Vs=0 V, 2.0 eV at Vs=90 V and 1.89 eV at Vs=180 V) clearly hinted the existence of a point of inflection in the properties of DLC films deposited using FAB source this way. A parameter ‘ D’ defined as the distance between the maximum of positive going excursion and the minimum of negative going excursion was calculated in the derivative XAES spectra. The values of ‘ D’ evaluated from XAES data for DLC films were found to be 14.8, 14.5 and 15.2 at Vs=0, 90 and 180 V, respectively. The sp 2 percentage was calculated for samples deposited this way and was found to be low and lie approximately at 5.6, 2.8, 2.3, 5.7 and 11.5 for different values of Vs=0, 50, 90, 150 and 180 V. The sp 3 content percentage and sp 3/sp 2 ratio was found to be 94.4 and 16.7, 97.7 and 42.5 at Vs=0 and 90 V, respectively. Beyond Vs=90 V these values started decreasing. Mainly, a point of inflection in all the properties of DLC films studied over here at around 90 V of applied substrate bias has been observed, which has been explained on the basis of existing theories in the literature. 相似文献
6.
The electronic structure and vibrational spectrum of the C 60 film condensed on a 2H- MoS 2(0001) surface have been investigated by X-ray photoelectron spectroscopy (XPS), ul-traviolet photoelectron spectroscopy (UPS), Auger electron spectroscopy (AES) and infrared high-resolution electron-energy-loss spectroscopy (HREELS). AES analysis showed that at low energy side of the main transition, C 60 contains a total of three peaks just like that of graphite. However, the energy position of the KLL main Auger transition of C 60 looks like that of diamond, indicating that the hybridization of the carbon atoms in C 60 is not strictly in sp 2- bonded state but that the curvature of the molecular surface introduces some sp 2pz- bonded character into the molecular orbitals. XPS showed that the C 1s binding energy in C 60 was 285.0eV, and its main line was very symmetric and offered no indication of more than a single carbon species. In UPS measurement the valence band spectrum of C 60 within 10eV below the Fermi level (E F) shows a very distinct five-band structure that character-izes the electronic structure of the C 60 molecule. HREEL results showed that the spectrum obtained from the C 60 film has very rich vibrational structure. At least, four distinct main loss peaks can be identified below 200 meV. The most intense loss was recorded at 66 meV, and relatively less intense losses were recorded at 95, 164 and 197meV at a primary energy of electron beam E P = 2.0eV. The other energy-loss peaks at 46, 136, 157 and 186meV in HREEL spectrum are rather weak. These results have been compared to infrared spectrum data of the crystalline solid C 60 taken from recent literatures. 相似文献
7.
Most amorphous carbon(a-C)applications require films with ultra-thin thicknesses;however,the electronic structure and opto-electronic characteristics of such films remain unclear so far.To address this issue,we developed a theoretical model based on the density functional theory and molecular dynamic simulations,in order to calculate the electronic structure and opto-electronic characteristics of the ultra-thin a-C films at different densities and temperatures.Temperature was found to have a weak influence over the resulting electronic structure and opto-electronic characteristics,whereas density had a significant influence on these aspects.The volume fraction of sp3 bonding increased with density,whereas that of sp2 bonding initially increased,reached a peak value of 2.52 g/cm 3,and then decreased rapidly.Moreover,the extinction coefficients of the ultra-thin a-C films were found to be density-sensitive in the long-wavelength regime.This implies that switching the volume ratio of sp2 to sp3 bonding can effectively alter the transmittances of ultra-thin a-C films,and this can serve as a novel approach toward photonic memory applications.Nevertheless,the electrical resistivity of the ultra-thin a-C films appeared independent of temperature.This implicitly indicates that the electrical switching behavior of a-C films previously utilized for non-volatile storage applications is likely due to an electrically induced effect and not a purely thermal consequence. 相似文献
8.
常温下对低压化学气相沉积制备的纳米硅镶嵌结构的a-SiN x:H薄膜进行低能量高剂量的C +注入后,在800~1200℃高温进行常规退火处理。X射线光电子能谱(XPS)及X射线光电子衍射(XRD)等实验结果表明,当退火温度由800℃升高到1200℃后,薄膜部分结构由SiC xN y转变成SiN x和SiC的混合结构。低温下利用真空紫外光激发,获得分别来自于SiN x、SiC xN y、SiC的,位于2.95,2.58,2.29 eV的光致发光光谱。随着退火温度的升高,薄膜的结构发生了变化,发光光谱也有相应的改变。 相似文献
9.
The investigations on the properties of HfO 2 dielectric layers grown by metalorganic molecular beam epitaxy were performed. Hafnium-tetra- tert-butoxide, Hf(C 4H 9O) 4 was used as a Hf precursor and pure oxygen was introduced to form an oxide layer. The grown film was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and capacitance–voltage ( C– V) and current–voltage ( I– V) analyses. As an experimental variable, the O 2 flow rate was changed from 2 to 8 sccm while the other experimental conditions were fixed. The XPS spectra of Hf 4f and O 1s shifted to the higher binding energy due to the charge transfer effect and the density of trapped charges in the interfacial layer was increased as the oxygen flow rate increased. The observed microstructure indicated the HfO 2 layer was polycrystalline, and the monoclinic phases are the dominant crystal structure. From the C– V analyses, k = 14–16 and EOT = 44–52 were obtained, and the current densities of (3.2–3.3) × 10 −3 A/cm 2 were measured at −1.5 V gate voltage from the I– V analyses. 相似文献
10.
Mo, Au and their coadsorbed layers were produced on nearly stoichiometric and oxygen-deficient titania surfaces by physical vapor deposition (PVD) and characterized by low energy ion scattering (LEIS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning tunnelling microscopy (STM). The behavior of Au/Mo bimetallic layers was studied at different relative metal coverages and sample temperatures. STM data indicated clearly that the deposition of Au on the Mo-covered stoichiometric TiO2(1 1 0) surface results in an enhanced dispersion of gold at 300 K. The mean size of the Au nanoparticles formed at 300 K on the Mo-covered TiO2(1 1 0) was significantly less than on the Mo-free titania surface (2 ± 0.5 nm and 4 ± 1 nm, respectively). Interestingly, the deposition of Mo at 300 K onto the stoichiometric TiO2(1 1 0) surface covered by Au nanoparticles of 3–4 nm (0.5 ML) also resulted in an increased dispersity of gold. The driving force for the enhanced wetting at 300 K is that the Au–Mo bond energy is larger than the Au–Au bond energy in 3D gold particles formed on stoichiometric titania. In contrast, 2D gold nanoparticles produced on ion-sputtered titania were not disrupted in the presence of Mo at 300 K, indicating a considerable kinetic hindrance for breaking of the strong Au-TiOx bond. The annealing of the coadsorbed layer formed on a strongly reduced surface to 740 K did not cause a decrease in the wetting of titania surface by gold. The preserved dispersion of Au at higher temperatures is attributed to the presence of the oxygen-deficient sites of titania, which were retained through the reaction of molybdenum with the substrate. Our results suggest that using a Mo-load to titania, Au nanoparticles can be produced with high dispersion and high thermal stability, which offers the fabrication of an effective Au catalyst. 相似文献
11.
The adsorption and dissociation of CH 2I 2 were studied at 110 K with the aim of generating CH 2 species on the Ru(001) surface. The methods used included X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), temperature programmed desorption (TPD), Auger electron spectroscopy (AES) and work function measurements. Adsorption of CH 2I 2 is characterized by a work function decrease (0.96 eV at monolayer), indicating that adsorbed CH 2I 2 has a positive outward dipole moment. Three adsorption states were distinguished: a multilayer ( Tp=200 K), a weakly bonded state ( Tp=220 K) and an irreversibly adsorbed state. A new feature is the formation of CH 3I, which desorbs with Tp=160 K. The adsorption of CH 2I 2 at 110 K is dissociative at submonolayer, but molecular at higher coverages. Dissociation of the monolayer to CH 2 and I proceeded at 198–230 K, as indicated by a shift in the I(3d 5/2) binding energy from 620.6 eV to 619.9 eV. A fraction of adsorbed CH 2 is self-hydrogenated into CH 4 ( Tp=220 K), and another one is coupled to di-σ-bonded ethylene, which — instead of desorption — is converted to ethylidyne at 220–300 K. Illumination of the adsorbed CH 2I 2 initiated the dissociation of CH 2I 2 monolayer even at 110 K, and affected the reaction pathways of CH 2. 相似文献
12.
We report the synthesis of Fe–Al nanopins using arc discharge. The morphology and chemical composition of the Fe–Al nanopins were studied by means of X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HRTEM). The nanopins are composed of a spherical base of about 20–100 nm and a needle-like tip of about several hundred nanometers. EDX and HRTEM studies indicate that the spherical base is mainly composed of -Fe and FeAl core coated with a thin Al 2O 3 layer, while the needle-like part contains only Al and O and corresponds to Al 2O 3. The formation mechanism of the nanopins is suggestive of a vapor–liquid–solid (VLS) growth process. The as-prepared Fe–Al nanopins show ferromagnetic properties. The temperature dependence of the magnetization at high temperatures indicates the existence of some phase transformations. 相似文献
13.
The efficacy of the surface treatment of particulate fillers depends on the chemical character of the components, on the method and conditions of the treatment, and on the amount of the treating agent. Here, the ultra-fine calcium carbonate is surface treated with 1, 2, 3 and 4 wt.% polyacrylic acid (PAA) synthesized by ourselves, which has strong ionic interaction and is an efficient surface modifier. The PAA coated filler is submitted to the measurement of the surface bonded amount, bonding efficacy, X-ray photoelectron spectroscopy (XPS) and inverse gas chromatography. Maximum efficacy is expected at the monolayer coverage of the surface, which is about 0.6 wt.% according to the calculation based on the way they are aligned and is basically in agreement with the “substrate overlayer” model based on the mole ratio of C 286 and C 290 taking no account of the possible underestimation because of the inaccuracy or because of the CH x contamination present originally on the CaCO 3. The initial decrease of the mole ratio of C 290/O and C 290/Ca with the surface bonded PAA may indicate that the bonding interaction between the polymer and the filler surface is the leaving of one molecular carbon dioxide. The IGC measurement shows that there is a considerable surface tension falling in the case of the PAA modified filler compared with the reference. An abnormal high surface energy in the case of filler treated with 4% PAA is observed. 相似文献
14.
Hard amorphous carbon films produced using high-energy (ca. 30 keV) ion beam deposition of CH 3+ and CH 4+ on silicon wafers, have been investigated by Positron Annihilation Spectroscopy (PAS), the results are correlated with Raman Spectroscopy and Electrical Resistivity measurements. The microstructural modifications of the films as a function of the annealing temperature in the 300–600°C range have been studied. The evolution of the fractions of sp 2 and sp 3 bonds is described and related to the changes of the open volume defect distribution and the graphitization process. 相似文献
15.
Carbon has three hybridization forms of sp −, sp 2− and sp 3−, and the combination of different forms can obtain different kinds of carbon allotropes, such as diamond, carbon nanotubes, fullerene, graphynes (GYs) and graphdiyne (GDY). Among them, the GDY molecule is a single-layer two-dimensional (2D) planar structure material with highly π-conjugation formed by sp − and sp 2− hybridization. GDY has a carbon atom ring composed of benzene ring and acetylene, which makes GDY have a uniformly distributed pore structure. In addition, GDY planar material have some slight wrinkles, which makes GDY have better self-stability than other 2D planar materials. The excellent properties of GDY make it attract the attention of researchers. Therefore, GDY is widely used in chemical catalysis, electronics, communications, clean energy and composite materials. This paper summarizes the recent progress of GDY research, including structure, preparation, properties and application of GDY in the field of catalysts. 相似文献
16.
The surface of 310 stainless steel (310SS) samples was investigated by X-ray photoelectron spectroscopy (XPS) after 500 h cyclic exposure to two carburizing atmospheres: CH 4 (2%)–H 2 (98%) at 800 °C, and CH 4 (10%)–H 2 (90%) at 1100 °C. The depth distribution of various elements in the surface region was obtained by XPS after successive cycles of argon etching. The microstructure of the alloy was observed by scanning electron microscopy (SEM) and the phases formed during the exposure were analyzed by X-ray diffraction (XRD). The results showed that the major phases that were formed within few micrometer depth during exposure at 800 °C include both iron and chromium carbides. (Mn, Cr) oxide was also formed as a result of the reaction with the residual oxygen of the atmosphere. A region of few microns width that was relatively depleted of chromium was formed under the surface as a result of the outwards diffusion of chromium. The exposure to the reducing atmosphere at 1100 °C led to the formation of various iron and chromium carbides. No oxide was formed during exposure. In all exposed samples, the surface was Cr enriched while nickel remained buried under the surface region that reacted with the atmosphere. 相似文献
17.
The corrosion resistance of uranium is greatly enhanced by alloying with niobium. In this study the initial stages of corrosion of a specific uranium-base alloy (U–14.1 at.% Nb) by O 2 or D 2O have been examined using the surface specific techniques of X-ray photoelectron spectroscopy (XPS), thermal programmed desorption (TPD), static secondary-ion mass spectroscopy (SSIMS), and sputtered neutrals mass spectroscopy (SNMS). XPS studies of the U–14.1 at.% Nb surface following oxidation using O 2 at 300 K indicate production of a thin oxide overlayer of stoichiometric UO 2.0 intermixed with Nb 2O 5. The same stoichiometry is exhibited for uranium when the oxide is prepared at 500 K with O 2; although, niobium is much less oxidized exhibiting a mixture of NbO and Nb. Contrary to previous XPS literature, SNMS depth profiling studies reveal that oxidation by O 2 is much greater (as judged by oxide layer thickness) than that exhibited by D 2O. An oxide layer thickness of less than 20 Å was created using D 2O as an oxidant at 300 K with exposures >3500 L (oxide layers created from O 2 are significantly greater at much smaller exposures). Formation of a critical density of Nb 2O 5 is suggested to be responsible for the enhanced corrosion resistance by preventing diffusion of O − (O 2−) or OD −/OH − into the oxide/metal interface region. The domains of stability of hydroxyl formation have also been followed using TPD, SSIMS and XPS. Maximal surface hydroxyl concentrations ( Θrel=0.30) are obtained at a surface temperature of 175 K for these experimental conditions. 相似文献
18.
The interaction of 180 fs, 775 nm laser pulses with aluminium under a flowing stream of helium at ambient pressure have been used to study the material re-deposition, ablation rate and residual surface roughness. Threshold fluence Fth0.4 J cm −2 and the volume ablation rate was measured to be 30< V<450 μm 3 per pulse in the fluence range 1.4< F<21 J cm −2. The presence of helium avoids gas breakdown above the substrate and leads to improved surface micro-structure by minimising surface oxidation and debris re-deposition. At 1 kHz rep. rate, with fluence F>7 J cm −2 and >85 W cm −2 average power density, residual thermal effects result in melt and debris formation producing poor surface micro-structure. On the contrary, surface micro-machining at low fluence F1.4 J cm −2 with low power density, 3 W cm −2 produces much superior surface micro-structuring with minimum melt and measured surface roughness Ra1.1±0.1 μm at a depth D50 μm. By varying the combination of fluence/scan speed during ultra-fast ablation of aluminium at 1 kHz rep. rate, results suggest that maintaining average scanned power density to <5 W cm −2 combined with single pulse fluence <4 J cm −2 produces near optimum micro-structuring. The debris under these conditions contains pure aluminium nanoparticles carried with the helium stream. 相似文献
19.
We have shown that, for thermally evaporated Ta 2O 5 or ZrO 2 thin films on Si(1 0 0), O 2 annealing at 300–500 °C causes the formation of an interfacial silicon oxide layer as thin as 1–2 nm which can be interpreted in terms of their high permeability to oxygen. And we have demonstrated how useful the energy loss spectra of photoexcited electrons from core levels such as O 1s are to measure the energy bandgaps of very thin insulators. With the combination of measured bandgaps and valence band lineups determined for X-ray photoelectron spectroscopy valence band spectra, we have determined the energy band alignments of Ta 2O 5 and ZrO 2 with Si(1 0 0) before and after the O 2 annealing at 500 °C. In addition, we have demonstrated that total photoelectron yield spectroscopy provides us direct information to quantify the energy distributions of both the defect states in the high-k dielectrics and the dielectric/Si(1 0 0) interface states over nearly entire Si bandgap. 相似文献
20.
In very rare circumstances, X-ray photoemission spectra of copper in spinel oxides exhibit a “negative binding energy shift”. The origin of such an anomalous XPS chemical shift was investigated. A metastable Ni 0.48Co 0.24Cu 0.6+xMn 1.68−xO 4 (0 < x < 0.6) spinel was fabricated at 600 °C using a low-temperature solution technique. The binding energy of the 2p 3/2 level of copper (930.8 eV) is found 1.9 eV lower than that of Cu 0 (932.7 eV). XPS and EXAFS studies revealed that the post-thermal annealing between 600 and 800 °C undergoes an irreversible cubic-to-tetragonal phase transformation through oxidation–reduction reaction Cu 1+ + Mn 4+ Cu 2+ + Mn 3+, and only tetrahedral Cu 1+ species in the cubic spinel shows this anomalous chemical shift. The negative shift of the core levels was correlated to an equal shift of the Cu 3d valence band levels. XPS valence bands from the samples annealed at different temperatures were compared to DOS calculations. The DOS computations were performed with FEFF-8.1 code using experimental crystal parameters established by the EXAFS analysis. It was found that the tetrahedral Cu 1+ in the 600 °C annealed sample exhibits localization of the 3d orbitals showing behavior characteristic to zinc. The completely filled and isolated 3d electron shell appears as a false valence band edge in the XPS spectrum. The position of the Cu 3d, and other core levels, is established by oxygen pinning the Cu valence band levels and by the fixed value of the p–d gap characteristic to the tetrahedral copper environment in this spinel. 相似文献
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