共查询到20条相似文献,搜索用时 15 毫秒
1.
《Diamond and Related Materials》2000,9(3-6):654-657
Hydrogenated amorphous carbon (a-C:H) films have been deposited from acetylene gas in a microwave electron cyclotron resonance (ECR) plasma reactor. The films were deposited at a pressure of 0.2 mTorr and at radio frequency (r.f.) induced substrate biases from 80–300 V. Selected film properties, including optical bandgap and bonded hydrogen content, were measured. At r.f. induced biases from 150 to 300 V, corresponding to ion energies for C2H2+ of approximately 150–300 eV, the hydrogen content remains constant and the optical bandgap peaks at a bias of 200 V, or approximately 100 eV per carbon in the C2H2+ ions. This ECR system result is in agreement with those observed by other researchers using different deposition methods where an optical bandgap maximum and an sp3 maximum occurs at ion energies of 90–100 eV per carbon atom. The discharge properties measured include a partial pressure analysis of the residual exit gas and the substrate current density. 相似文献
2.
Sausan Al-Riyami Shinya Ohmagari Tsuyoshi Yoshitake 《Diamond and Related Materials》2010,19(5-6):510-513
Nitrogen-doped ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were deposited by pulsed laser deposition (PLD). Nitrogen contents in the films were controlled by varying a ratio in the inflow amount between nitrogen and hydrogen gases. The film doped with a nitrogen content of 7.9 at.% possessed n-type conduction with an electrical conductivity of 18 Ω? 1 cm? 1 at 300 K. X-ray photoemission spectra, which were measured using synchrotron radiation, were decomposed into four component spectra due to sp2, sp3 hybridized carbons, C=N and C–N. A full-width at half-maximum of the sp3 peak was 0.91 eV. This small value is specific to UNCD/a-C:H films. The sp2/(sp3 + sp2) value was enhanced from 32 to 40% with an increase in the nitrogen content from 0 to 7.9 at.%. This increment probably originates from the nitrogen incorporation into an a-C:H matrix and grain boundaries of UNCD crystallites. Since an electrical conductivity of a-C:H does not dramatically enhance for this doping amount according to previous reports, we believe that the electrical conductivity enhancement is predominantly due to the nitrogen incorporation into grain boundaries. 相似文献
3.
J.-C. Arnault S. Saada Sh. Michaelson N.K. Hangaly R. Akhvlediani A. Hoffman 《Diamond and Related Materials》2008,17(3):377-382
The nature of hydrogen and carbon bonding configuration formed onto 3C–SiC(100) surfaces by the diamond bias enhanced nucleation process consisting of stabilization and biasing stages were investigated by high resolution electron energy loss spectroscopy and high resolution X-ray photoelectron spectroscopy. During the stabilization stage a sp3-CHx bonded carbonaceous mono-layer is formed onto a hydrogenated 3C–SiC(100)–C–H terminated surfaces. After the biasing stage a hydrogenated nano-diamond film is formed. It was determined that hydrogen is strongly bonded to these nano-diamond surfaces and boundaries in sp3-C–H and sp2-C–H mono-hydride configuration. In addition, CHx (x > 1) weakly bonded surface or sub-surface species were detected. Regions which are not fully covered by the nano-diamond film expose the SiC surface covered with a very thin carbonaceous layer. 相似文献
4.
K. Ozeki H. Saitoh M. Takeda Y. Ohgoe K.K. Hirakuri M. Yonemura T. Masuzawa 《Diamond and Related Materials》2010,19(5-6):489-491
The cross-sectional profiles of hydrogen content and mass density of diamond-like carbon (DLC) film were investigated using X-ray and neutron reflectivity. DLC films were prepared using a plasma CVD technique by varying the H2/(H2 + CH4) ratio gas source from 0 to 0.9. The cross-sectional hydrogen content and mass density profiles of the films were calculated by neutron and X-ray reflectivity, and the results were compared with those from elastic recoil detection analysis (ERDA).The fitted simulation showed that the mass density gradually decreased with increasing depth, whereas the hydrogen content increased with depth. In both ERDA and reflectivity measurements, the average hydrogen content was more than 30% in all films and tended to increase with the H2/(CH4 + H2) ratio. However, there was a difference in hydrogen content values between the two analyses ranging from 5.1 % to 8.5%. 相似文献
5.
Poly- and nanocrystalline diamond films have been deposited using microwave plasma enhanced CVD with gas mixtures of x%CH4/15%H2/Ar (x = 0.5, 1, 3, and 5). After deposition the resulting films were exposed to a hydrogen plasma etching for 30 min. The hydrogen plasma produced preferential etching of non-diamond carbon on the surface of the samples and the development of steps and pits. Raman spectroscopy and X-ray photoelectron spectroscopy analyses on the etched films showed increased sp3/sp2 ratio and decreased surface oxygen. The etch mechanism proposed is regression of pre-existing steps and step flow. 相似文献
6.
《Diamond and Related Materials》1999,8(2-5):446-450
Amorphous carbon films were deposited by r.f. magnetron sputtering at various bias voltages Vb applied on Si substrate. We studied the optical properties of the films using in situ spectroscopic ellipsometry (SE) measurements in the energy region 1.5–5.5 eV. From the SE data analysis the dielectric function ε(ω) of the a-C films was obtained, providing information about the electronic structure and the bonding configuration of a-C films. Based on the SE data the films are classified in three categories. In Category I and II belong the films developed with Vb≥0 V (rich in sp2 bonds) and −100≤Vb<0 V (rich in sp3 bonds), respectively. The dielectric function of the films belonging in these two categories can be described with two Lorentz oscillators located in the energy range 2.5–5 eV (π–π*) and 9–12 eV (σ–σ*). A correlation was found between the oscillator strength and the sp2 and sp3 contents. The latter were calculated by analyzing the ε(ω) with the Bruggeman effective medium theory. In films deposited with Vb<−100 V (Category III), the formation of a new and dense carbon phase was detected which exhibits a semi-metallic optical behavior and the ε(ω) can be described with two oscillators located at ∼1.2 and ∼5.5 eV. 相似文献
7.
《Diamond and Related Materials》2007,16(2):209-215
A detailed study of the top surface (∼ 2 nm) of a near frictionless carbon film has revealed new information with respect to the sp3 fraction. Previous work on near frictionless carbon films made at Argonne had shown a large fraction of sp2-hybridized carbon in the bulk of the film. However, in this study of the surface, the majority of the carbon was found to be sp3. In addition we compared and contrasted the behavior of the films after mechanical abrasion and Ar+ etching. The study also revealed that oxygen on untreated samples was rapidly reduced by etching or heating or mechanical abrasion; this finding was corroborated by an angle-resolved study, where different depths of the sample were probed. It was also found that the fraction of sp3 carbon decreased linearly with depth, falling in one film from ∼ 90% sp3 to ∼ 80% sp3 in the top 2 nm. 相似文献
8.
A comparative study of the tribological properties of a library of different carbon forms is presented. The library includes hydrogen free and hydrogenated carbon films with different bonding (CC, CH, different sp3 fractions) and structure configurations (amorphous, graphitic) leading to a wide range of densities and hardness. Reference samples (Si substrates, thermally evaporated amorphous carbon, graphitic foil) were studied as well. The tribological properties were measured using a reciprocal sliding tribometer under humid (50% RH) and dry (5% RH) air conditions. Friction coefficients were measured versus the number of sliding cycles and the wear was studied using optical profilometry and imaging as well as SEM.The friction and wear performance of the carbon films were found to depend on both the structure and the ambient conditions. Hydrogen free films have friction coefficients < 0.1 for 80% sp3 bonded films and > 0.1 for 100% sp2 bonded films. The wear resistance of the hydrogen free films (much larger for sp3 bonded films) significantly decreases under dry conditions. In contrast, hydrogenated films show reduction in friction with decreasing humidity (from 0.2 under 50% RH to < 0.1 under 5% RH). The wear resistance of hydrogenated films is larger for dry and smaller for humid conditions. 相似文献
9.
DLC films were deposited by a new pulsed DC discharge plasma chemical vapour deposition (CVD) using hydrogen and methane gas mixture. When methane concentration (Cm) i.e. CH4/(H2 + CH4) was increased from 3 to 40%, the graphitization of the carbon film increases as evident from Raman study. When Cm was increased to 30%, DLC film shows photoconducting property. The white light photoconductivity (S = Il/Id, where Il is light current and Id is dark current) measured with solar simulator under AM 1.5 condition was approximately 20 at room temperature. The photoconductivity was not clear when Cm was lower than 20%. ESR measurements also show that the electron spin density was slightly decreased with decreasing concentration of methane. Thus we can conclude here that at higher concentrations of methane at 30%, Sp2 content of the film increases and the DLC film becomes photoconducting. 相似文献
10.
D. Ballutaud F. Jomard T. Kociniewski E. Rzepka H. Girard S. Saada 《Diamond and Related Materials》2008,17(4-5):451-456
Hot filament and microwave plasma CVD micro- nanocrystalline diamond films are analysed by visible and ultra-violet excitation source Raman spectroscopy. The sample grain size varies from 20 nm to 2 μm. The hydrogen concentration in samples is measured by SIMS and compared to the grain size, and to the ratio of sp2 carbon bonds determined by Raman spectroscopy from the 1332 cm− 1 diamond peak and the sp2 1550 cm− 1 G band. Hydrogen concentration appears to be proportional to the sp2 bonds ratio. The 3000 cm− 1 CHx stretching mode band intensity observed on the Raman spectra is decreasing with the G band intensity. Thermal annealing modifies the sp2 phase structure and concentration, as hydrogen outdiffuses. 相似文献
11.
H. Sabbah S. Ababou-Girard A. Zebda D. David B. Fabre S. Députier A. Perrin M. Guilloux-Viry F. Solal C. Godet 《Diamond and Related Materials》2009,18(9):1074-1080
Thermally-assisted (160 °C) liquid phase grafting of linear alkene molecules has been performed simultaneously on amorphous carbon (a-C) and hydrogen passivated crystalline silicon Si(111):H surfaces. Atomically flat a-C films with a high sp3 average surface hybridization, sp3 / (sp2 + sp3) = 0.62, were grown using pulsed laser deposition (PLD). Quantitative analysis of X-ray photoelectron spectroscopy, X-ray reflectometry and spectroscopic ellipsometry data show the immobilization of a densely packed (> 3 × 1014 cm? 2) single layer of organic molecules. In contrast with crystalline Si(111):H and other forms of carbon films, no surface preparation is required for the thermal grafting of alkene molecules on PLD amorphous carbon. The molecular grafted a-C surface is stable against ambient oxidation, in contrast with the grafted crystalline silicon surface. 相似文献
12.
《Carbon》2014
The first- and second-order Raman spectra of carbon nano-onions (CNOs), produced via annealing of detonation nanodiamonds with a mean grain size of ∼5 nm in the argon ambience at the maximal temperature of annealing process (TMAX) varying from 1500 to 2150 °C, are analyzed together with the high-resolution transmission electron microscopy (HRTEM) images. The combined analysis provides a deep insight into the annealing-induced atomic-scale structural modifications of the CNO nanoparticles. The Raman and HRTEM data unambiguously demonstrate the reduction in the number of defects in the CNO structure, as well as indicate the conversion from the diamond sp3-bonded carbon phase to the sp2-bonded carbon phase with increasing TMAX and its almost full completion for TMAX = 1600 °C. 相似文献
13.
《Diamond and Related Materials》2006,15(10):1732-1737
Structural and mechanical properties of carbon nitride films, deposited using a DC facing-target reactive sputtering system at various N2 fractions (PN) in the gas mixture, were studied systematically. XPS analyses indicate that N concentration is not directly proportional to PN, and it rises quickly to a saturation value of ∼ 33 at.% at a PN of 20%. The ratio of N–C(sp2)/N–C(sp3) increases with the rise of PN from 0% to 20%, and then decreases with further rising PN. However, the number and size of disordered sp2-hybridized C clusters continue to increase over the whole range of PN, which is consistent with the Raman and high-resolution transmission electron microscopy measurements. Nanoindenter measurements show that the hardness of the films continuously decreases from ∼ 17.5 to ∼ 5.6 GPa with the increasing PN from 0% to 100%, due to the conversion from sp3 C to sp2 C and the clustering of sp2 C structure. 相似文献
14.
Optical and microstructural properties of diamond-like carbon films grown by pulsed laser deposition
《Diamond and Related Materials》2007,16(1):149-154
Diamond-like carbon films have been fabricated using 308 nm excimer laser ablation in vacuum followed by deposition at temperatures between 77 K and 573 K. Optical band gap energies are obtained from UV/optical spectroscopy. Raman spectra and X-ray photoelectron spectra (XPS) show that the sp3/(sp2 + sp3) ratio in these films is in excess of 0.7 in films deposited at 77 K and 300 K. This ratio decreases to 0.2 in films deposited at 573 K. It is found that films deposited at cryogenic temperatures consist of a matrix structure assembled from embedded nanometer clusters, while films deposited at 300 K or higher temperature are amorphous and atomically flat. Microstructural features in cryogenic films are discussed in relation to the mechanism of deposition and possible phase transitions during assembly of these films. 相似文献
15.
D. Ballutaud T. Kociniewski J. Vigneron N. Simon H. Girard 《Diamond and Related Materials》2008,17(7-10):1127-1131
The hydrogen concentration in hot filament and microwave plasma CVD nanocrystalline diamond films is analysed by secondary ion mass spectrometry and compared to the film grain size. The surface and bulk film carbon bonds are analysed respectively by X-ray photoelectron spectroscopy (XPS) and ultra-violet Raman spectroscopy. XPS results show the presence of the hydrogenated p-type surface conductive layer. The respective intensities of the 1332 cm− 1 diamond peak, of the G and D bands related to sp2 phases, and of the 3000 cm− 1 CHx stretching mode band, are compared on Raman spectra. The samples are submitted to thermal annealing under ultra-high vacuum in order to get hydrogen out-diffusion. XPS analysis shows the surface desorption of hydrogen. Thermal annealing modifies the sp2 phase structure as hydrogen out diffuses. 相似文献
16.
Sathyaharish Jeedigunta Zhenqing Xu Makoto Hirai Priscila Spagnol Ashok Kumar 《Diamond and Related Materials》2008,17(12):1994-1997
The nitrogen incorporated nanocrystalline diamond (NCD) films were grown on n-silicon (100) substrates by microwave plasma enhanced chemical vapor deposition (MPECVD) using CH4/Ar/N2 gas chemistry. The effect of surface passivation on the properties of NCD films was investigated by hydrogen and nitrogen-plasma treatments. The crystallinity of the NCD films reduced due to the damage induced by the plasma treatments. From the crystallographic data, it was observed that the intensity of (111) peak of the diamond lattice reduced after the films were exposed to the nitrogen plasma. From Raman spectra, it was observed that the relative intensity of the features associated with the transpolyacetylene (TPA) states decreased after hydrogen-plasma treatment, while such change was not observed after nitrogen-plasma treatment. The hydrogen-plasma treatment has reduced the sp2/sp3 ratio due to preferential etching of the graphitic carbon, while this ratio remained same in both as-grown and nitrogen-plasma treated films. The electrical contacts of the as-grown films changed from ohmic to near Schottky after the plasma treatment. The electrical conductivity reduced from ~ 84 ohm– 1 cm− 1 (as-grown) to ~ 10 ohm– 1 cm− 1 after hydrogen-plasma treatment, while the change in the conductivity was insignificant after nitrogen-plasma treatment. 相似文献
17.
Amorphous carbon (a-C) films with various thicknesses depending on the reaction time are deposited on the surface of Ti1.4V0.6Ni alloy electrodes for Ni-MH (nickel-metal hydride) battery by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). With the increasing deposition time, the Raman spectra show a gradually disordered sp2-bonding change of the films and the changing trend of sp2/sp3 is obtained by X-ray photoelectron spectroscopy. The a-C film of depositing for 30 min with the thickness of 400 nm shows a favorable stability in alkaline electrolyte, the capacity is enhanced by 36.2% after 50 cycles than the bare electrode, and the charge voltage is 80 mV lower than the bare one. The a-C film with high sp2-bonded carbon content effectively reduces the charge transfer resistance, and as a coating layer, the dissolution of V of the alloy is also inhibited. In particular, to get a proper discharge voltage and a stable capacity simultaneously, covering completely and an appropriate thickness of the a-C film are crucial for an expected performance. 相似文献
18.
We have deposited unhydrogenated diamond-like carbon (DLC) films on Si substrate by pulsed laser deposition using KrF excimer laser, and investigated the effects of atomic-hydrogen exposure on the structure and chemical bonding of the DLC films by photoelectron spectroscopy (PES) using synchrotron radiation and Raman spectroscopy. The fraction of sp3 bonds at the film surface, as evaluated from C1s spectra, increased at a substrate temperature of 400 °C by atomic-hydrogen exposure, whereas the sp3 fraction decreased at 700 °C with increasing exposure time. It was found that the sp3 fraction was higher at the surfaces than the subsurfaces of the films exposed to atomic hydrogen at both the temperatures. The Raman spectrum of the film exposed to atomic hydrogen at 400 °C showed that the clustering of sp2 carbon atoms progressed inside the film near the surface even at such a low temperature as 400 °C. 相似文献
19.
Tetrahedral amorphous carbon (a-C) films have been grown by pulsed laser deposition to investigate a liquid phase process for surface immobilization of electroactive [Mo6Ii8]4 + transition metal cluster cores using a complexation reaction with a pyridine-terminated alkyl monolayer covalently bonded to the a-C surface (PyS–alkyl/a-C). These films are stable against thermally-assisted grafting of alkene molecules and the covalent CC interface provides a robust monolayer/a-C assembly. Octahedral [Mo6Ii8]4 + cluster cores with iodine inner ligands and labile triflate apical ligands [Mo6Ii8(CF3SO3)a6]2 − have been immobilized through partial complexation in apical positions by surface pyridine groups (PyS). The remaining CF3SO3− apical ligands of [Mo6Ii8 (PyS)ay(CF3SO3)a6 − y] cluster units were further substituted with bromopyridine (Py-Br) to obtain air stable surface with expected final composition [Mo6Ii8 (PyS)ay(Py-Br)a6 − y]. The yield of the different reaction steps is followed by X-ray photoelectron spectroscopy, providing cluster coverage ΣMo6I8 = 9 × 1012 cm− 2. Each [Mo6I8]4 + cluster is bound to the carbon surface through multiple anchoring metal sites (NPYR = 3 or 4), indicating that pyridine-terminated alkyl chains are flexible enough to accommodate four bonds. Electrical transport through Hg//Mo6I8–PyS–alkyl/a-C/p-Si(111) junctions shows rectifying current–voltage characteristics but does not reveal any signature of cluster immobilization. 相似文献
20.
Sathyaharish Jeedigunta Priscila Spagnol John Bumgarner Ashok Kumar 《Diamond and Related Materials》2008,17(12):2037-2040
The effect of surface plasma treatment on the nature of the electrical contact to the nitrogen incorporated nanocrystalline diamond (n-NCD) films is reported. Nitrogen incorporated NCD films were grown in a microwave plasma enhanced chemical vapor deposition (MPECVD) reactor using CH4 (1%)/N2 (20%)/Ar (79%) gas chemistry. Raman spectra of the films showed features at ∼ 1140 cm− 1, 1350 cm− 1(D-band) and 1560 cm− 1(G-band) respectively with changes in the bonding configuration of G-band after the plasma treatment. Electrical contacts to both untreated and surface plasma treated films are formed by sputtering and patterning Ti/Au metal electrodes. Ohmic nature of these contacts on the untreated films has changed to non-ohmic type after the hydrogen plasma treatment. The linear current–voltage characteristics could not be obtained even after annealing the contacts. The nature of the electrical contacts to these films depends on the surface conditions and the presence of defects and sp2 carbon. 相似文献