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1.
Amorphous hydrogenated carbon (a-C:H) thin films deposited on a silicon substrate under various mixtures of methane-hydrogen gas by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD) was investigated. Microstructure, surface morphology and mechanical characterizations of the a-C:H films were analyzed using Raman spectroscopy, atomic force microscopy (AFM) and nanoindentation technique, respectively. The results indicated there was an increase of the hydrogen content, the ratio of the D-peak to the G-peak (ID/IG) increased but the surface roughness of the films was reduced. Both hardness and Young's modulus increased as the hydrogen content was increased. In addition, the contact stress-strain analysis is reported. The results confirmed that the mechanical properties of the amorphous hydrogenated carbon thin films improved using a higher H2 content in the source gas.  相似文献   

2.
a-C:H films were prepared by middle frequency plasma chemical vapor deposition (MF-PCVD) on silicon substrates from two hydrocarbon source gases, CH4 and a mixture of C2H2 + H2, at varying bias voltage amplitudes. Raman spectroscopy shows that the structure of the a-C:H films deposited from these two precursors is different. For the films deposited from CH4, the G peak position around 1520 cm−1 and the small intensity ratio of D peak to G peak (I(D)/I(G)) indicate that the C-C sp3 fraction in this film is about 20 at.%. These films are diamond-like a-C:H films. For the films deposited from C2H2 + H2, the Raman results indicate that their structure is close to graphite-like amorphous carbon. The hardness and elastic modulus of the films deposited from CH4 increase with increasing bias voltage, while a decrease of hardness and elastic modulus of the films deposited from a mixture of C2H2 + H2 with increasing bias voltage is observed.  相似文献   

3.
The a-C:H and a-C:NX:H films were deposited onto silicon wafers using radio frequency (rf) plasma enhanced chemical vapor deposition (PECVD) and pulsed-dc glow discharge plasma CVD, respectively. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize chemical nature and bond types of the films. The results demonstrated that the a-C:H film prepared by rf-CVD (rf C:H) has lower ID/IG ratio, indicating smaller sp2 cluster size in an amorphous carbon matrix. The nitrogen concentrations of 2.9 at.% and 7.9 at.% correspond to carbon nitride films prepared with rf and pulse power, respectively.Electrochemical corrosion performances of the carbon films were investigated by potentiodynamic polarization test. The electrolyte used in this work was a 0.89% NaCl solution. The corrosion test showed that the rf C:H film exhibited excellent anti-corrosion performance with a corrosion rate of 2 nA cm−2, while the carbon nitride films prepared by rf technique and pulse technique showed a corrosion rate of 6 nA cm−2 and 235 nA cm−2, respectively. It is reasonable to conclude that the smaller sp2 cluster size of rf C:H film restrained the electron transfer velocity and then avoids detriment from the exchange of electrons.  相似文献   

4.
Fe-doped hydrogenated amorphous carbon (a-C:H:Fe) films were deposited from a gas mixture of trans-2-butene/ferrocene/H2 by plasma enhanced metal organic chemical vapor deposition. X-ray photoelectron spectroscopy, Fourier transform infrared spectra and Raman spectra were used to characterize the composition and the bonding structure of the a-C:H:Fe and a-C:H films. Optical properties were investigated by the UV–visible spectroscopy and the photoluminescence (PL) spectra. The Fe-doped films contain more aromatic structures and C=C bonds than the undoped films. The sp 2 carbon content and sp 2 clustering of the films increase, and aromatic-like rings’ structures become richer after Fe-doping. The Tauc optical gap of the a-C:H:Fe films become narrower by 0.3 eV relative to the value of the a-C:H films. The PL peak shifts from 2.35 eV of the a-C:H films to 1.95 eV of the a-C:H:Fe films, and the PL intensity of the a-C:H:Fe films is greatly enhanced. A deep level emission peak around 2.04 eV of the a-C:H:Fe films is observed.  相似文献   

5.
Jun Xie 《哲学杂志》2013,93(11):820-832
Abstract

Ultrathin hydrogenated amorphous carbon (a-C:H) films deposited by plasma-enhanced chemical vapor deposition (PECVD) and hydrogen-free amorphous carbon (a-C) films of similar thickness deposited by filtered cathodic vacuum arc (FCVA) were subjected to rapid thermal annealing (RTA). Cross-sectional transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) were used to study the structural stability of the films. While RTA increased the thickness of the intermixing layer and decreased the sp3 content of the a-C:H films, it did not affect the thickness or the sp3 content of the a-C films. The superior structural stability of the FCVA a-C films compared with PECVD a-C:H films, demonstrated by the TEM and EELS results of this study, illustrates the high potential of these films as protective overcoats in applications where rapid heating is critical to the device functionality and performance, such as heat-assisted magnetic recording.  相似文献   

6.
In this work, we extracted the film's hardness (HF) of ultra-thin diamond-like carbon layers by simultaneously taking into account the tip blunting and the substrate effect. As compared to previous approaches, which did not consider tip blunting, this resulted in marked differences (30-100%) for the HF value of the thinner carbon coatings. We find that the nature of the substrate influences this intrinsic film parameter and hence the growth mechanisms. Moreover, the HF values generally increase with film thickness. The 10 nm and 50 nm thick hydrogenated amorphous carbon (a-C:H) films deposited onto Si have HF values of, respectively, ∼26 GPa and ∼31 GPa whereas the 10 nm and 50 nm thick tetrahedral amorphous carbon (t-aC) films deposited onto Si have HF values of, respectively, ∼29 GPa and ∼38 GPa. Both the a-C:H and t-aC materials also show higher density and refractive index values for the thicker coatings, as measured, respectively by X-ray reflectometry and optical profilometry analysis. However, the Raman analysis of the a-C:H samples show bonding characteristics which are independent of the film thickness. This indicates that in these ultra-thin hydrogenated carbon films, the arrangement of sp2 clusters does not relate directly to the hardness of the film.  相似文献   

7.
Characterization of the growth of hydrogenated amorphous silicon (a-Si:H) and carbon (a-C:H) thin films by in situ ellipsometric analysis at 3.4 eV and 3.2 eV is reported. For a-Si:H, prepared on metal substrates from an rf discharge of SiH4, in situ ellipsometry data are strongly influenced by the SiSi bond packing density in the growing film. Deviations in the data from model calculations assuming a thickness independent a-Si:H dielectric function, when analyzed using an effective medium approximation, reveal the geometry and scale of the initial nucleation process. Effects of the deposition conditions and substrate microstructure on the coalescence of initial nuclei are understood on the basis of new measurements. For a-C:H, prepared on c-Si substrates from CH4 by direct ion beam deposition, ellipsometry measurements in the initial stages of growth provide monolayer sensitivity to the formation of an absorbing SiCx layer at the substrate interface. Fits to the data in the later stages of growth establish the real and imaginary parts of the bulk dielectric function at 3.2 eV, allowing real time categorization of the nature of the bonding in such films.  相似文献   

8.
The structure and phase composition of thin a-C:H and a-C:H〈M〉 films (M = Ag, Ti, or Ag + Ti) have been studied by Raman and X-ray photoelectron spectroscopy. The a-C:H〈M〉 films were prepared by ion-plasma magnetron sputtering of a combined target of graphite and metal in an Ar–CH4 gas mixture. The Raman spectra of these films indicate that their structure is amorphous. The a-C:H〈Ag + Ti〉 films have a more graphitized structure in comparison with pure a-C:H films and films containing only one metal. It is established that carbon in the a-C:H〈Ag + Ti〉 films is in the sp 2, sp 3, and C=O states, which are characteristic of the a-C:H, a-C:H〈Ag〉, and a-C:H〈Ti〉 films. In addition, there are also ether (–C–O–C–) or epoxy (?C?O–) carbon groups in the a-C:H〈Ag + Ti〉 films. It has been revealed that silver atoms in the a-C:H〈Ag〉 and a-C:H〈Ag + Ti〉 films form no chemical bonds with carbon, oxygen, and titanium. Titanium in the a-C:H〈Ti〉 and a-C:H〈Ag + Ti〉 films exists in the form of titanium IV oxide (TiO2).  相似文献   

9.
The effect of nitrogen addition and laser fluence on the atomic structure of amorphous carbon films (a-C) synthesized by femtosecond pulsed laser deposition has been studied. The chemical bonding in the films was investigated by means of X-ray photoelectron (XPS) and Raman spectroscopies. XPS studies revealed a decrease in the sp3 bonded carbon sites and an associated increase in the N-sp2C bonding sites with increasing nitrogen content in the CNx films. An increase in laser fluence from 0.36 to 1.7 J/cm2 led to a rise in sp3C sites. These results were further confirmed by Raman spectroscopy. The ID/IG ratio increased monotonically and G line-width decreased with the increase of nitrogen content in the films indicating a rise in either the number or the size of the sp2 clusters. Furthermore a visible excitation wavelength dependence study established the resonant Raman process in a-C and CNx films. PACS 81.05.Uw; 81.15.Fg; 82.80  相似文献   

10.
In order to improve the adherence of DLC films, interlayers of amorphous hydrogenated carbon (a-C:H) and titanium nitride (TiN) were deposited by means of the pulsed vacuum arc technique. Bilayers were obtained by using a carbon target of 99.98% of purity in mixtures of (Ar + CH4) and (Ar + H2) for producing a-C and DLC, respectively and a target of titanium of 99.999% in a mixture of (Ar + N2) for growing TiN. After the deposition, chemical and morphological differences between TiN/DLC and a-C:H/DLC bilayers grown on silicon and stainless steel 304 were studied using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and scanning probe microscopy (SPM) techniques. XPS analysis showed a difference in sp3/(sp2+sp3) bonds ratio for each bilayer, being 0.67 for TiN/DLC and 0.45 for a-C:H/DLC bilayers. sp3 and sp2 bonds were also observed by the FTIR technique. SPM images, in atomic force microscopy (AFM) and lateral force microscopy (LFM) modes were carried out for illustrating the comparison between TiN/DLC and a-C/DLC morphologic characteristics. Roughness and grain size were studied as a function of the H2 concentration for both bilayers.  相似文献   

11.
Hydrogenated amorphous carbon (a-C:H) is a state-of-the-art material with established properties such as high mechanical resistance, low friction, and chemical inertness. In this work, a-C:H thin films were deposited by plasma-assisted chemical vapor deposition. The deposition process was enhanced by electrostatic confinement that leads to decrease the working pressure achieving relative high deposition rates. The a-C:H thin films were characterized by elastic recoil detection analysis, Rutherford backscattering spectroscopy, scanning electron microscopy, Raman spectroscopy, and nanoindentation measurements. The hydrogen content and hardness of a-C:H thin films vary from 30 to 45 at% and from 5 to 15 GPa, respectively. The hardness of a-C:H thin films shows a maximum as a function of the working pressure and is linearly increased with the shifting of the G-peak position and I D/I G ratio. The structure of a-C:H thin films suffers a clustering process at low working pressures. A physical model is proposed to estimate the mean ion energy of carbonaceous species arriving at the surface of a-C:H thin films as a function of processing parameters as pressure and voltage and by considering fundamentals scattering events between ion species and neutral molecules and atoms.  相似文献   

12.
Thin layers of hydrogenated amorphous carbon were prepared by using organic hydrocarbon source, xylene (C8H10), in plasma-enhanced chemical vapor deposition (PECVD) system. The microstructures were characterized by using Fourier-transform infrared and Raman scattering spectra. The appearance of a sharp vibration signal in 1600 cm-1 strongly suggests the existence of sp2 carbon clusters with aromatic rings. With increasing the deposition rf power, the content of these aromatic structures is increased in the films. In contrast to a broad single PL peak in methane (CH4)-baseda-C:H films, the PL band of xylene-based a-C:H films contains multiple peaks in blue-green light region, which is influenced by rf power. We tentatively attributed it to the radiative recombination of electron-hole pairs through some luminescent centers associated with aromatic structures. Received: 26 April 2000 / Accepted: 9 May 2000 / Published online: 13 September 2000  相似文献   

13.
Cr-containing hydrogenated amorphous carbon (Cr-C:H) films were deposited on silicon substrates using a DC reactive magnetron sputtering with Cr target in an Ar and C2H2 gas mixture. The composition, bond structure, mechanical hardness and elastic recovery of the films were characterized using energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and nano-indentation. The film tribological behavior was also studied by a ball-on-disc tribo-tester. The results showed that the films deposited at low C2H2 flow rate (<10 sccm) presented a feature of composite Cr-C:H structure, which consisted of hard brittle chromium carbide phases and amorphous hydrocarbon phase, and thus led to the observed low elastic recovery and poor wear resistance of the films. However, the film deposited at high C2H2 flow rate (40 sccm) was found to present a typical feature of polymer-like a-C:H structure containing a large amount of sp3 C-H bonds. As a result, the film revealed a high elastic recovery, and thus exhibited an excellent wear resistance.  相似文献   

14.
We have used Raman scattering, elemental analysis, and structural analysis to study the effect of the concentration of incorporated metals (Cu, Ni) on the ratio of sp2/sp3 carbon bonds in composite hydrogen-containing films a-C:H/Cu and a-C:H/Ni, formed by combining plasma-enhanced vapor phase deposition of carbon and sputtering of the metal, using a mixture of argon and methane or acetylene gases. We have shown that formation of a nanosized structure of metallic crystallites (2–5 nm) in the composite films leads to a significant increase in the fraction of disordered sp3-bonded carbon clusters and a decrease in the linear dimensions of the graphite-like carbon clusters. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 344–348, May–June, 2006.  相似文献   

15.
Diamond-like carbon (DLC) is an attractive biomedical material due to its high inertness and excellent mechanical properties. In this study, DLC films were fabricated on Ti6Al4V and Si(1 0 0) substrates at room temperature by pulsed vacuum arc plasma deposition. By changing the argon flow from 0 to 13 sccm during deposition, the effects of argon flow on the characteristics of the DLC films were systematically examined to correlate to the blood compatibility. The microstructure and mechanical properties of the films were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) surface analysis, a nano-indenter and pin-on-disk tribometer. The blood compatibility of the films was evaluated using in vitro platelet adhesion investigation, and the quantity and morphology of the adherent platelets was investigated employing optical microscopy and scanning electron microscopy.The Raman spectroscopy results showed a decreasing sp3 fraction (an increasing trend in ID/IG ratio) with increasing argon flow from 0 to 13 sccm. The sp3:sp2 ratio of the films was evaluated from the deconvoluted XPS spectra. We found that the sp3 fraction decreased as the argon flow was increased from 0 to 13 sccm, which is consistent with the results of the Raman spectra. The mechanical properties results confirmed the decreasing sp3 content with increasing argon flow. The Raman D-band to G-band intensity ratio increased and the platelet adhesion behavior became better with higher flow. This implies that the blood compatibility of the DLC films is influenced by the sp3:sp2 ratio. DLC films deposited on titanium alloys have high wear resistance, low friction and good adhesion.  相似文献   

16.
A series of hydrogenated amorphous carbon (a-C:H) films were deposited on silicon substrates by microwave plasma chemical vapor deposition technique with a mixture of hydrogen and acetylene. The effects of flow ratio of hydrogen to acetylene on surface morphology and structure of a-C:H films were investigated using surface-enhanced Raman spectroscopy and scanning probe microscope (SPM) in the tapping AFM mode. Raman data imply a transition from graphite-like phase to diamond-like bonding configurations when the flow ratio increases. AFM measurements show that the increase in hydrogen content, to some extent, can smoothen the surface morphology and decrease the RMS roughness. Excessive hydrogen is found to cause the formation of polymeric hydrocarbon clusters in the films and reduce deposition rate.  相似文献   

17.
Ultraviolet (UV) and visible Raman spectroscopy were used to study a-C:H:N films deposited using ECR-CVD with a mixed gas of CH4 and N2. Small percentage of nitrogen from 0 to 15% is selected. Raman spectra show that CN bonds can be directly observed at 2220 cm−1 from the spectra of visible and UV Raman. UV Raman enhances the sp1 CN peak than visible Raman. In addition, the UV Raman spectra can reveal the presence of the sp3 sites. For a direct correlation of the Raman parameter with the N content, we introduced the G peak dispersion by combining the visible and UV Raman. The G peak dispersion is directly relative to the disorder of the sp2 sites. It shows the a-C:H:N films with higher N content will induce more ordered sp2 sites. In addition, upper shift of T position at 244 nm excitation with the high N content shows the increment of sp2 fraction of films. That means the films with high N content will become soft and contain less internal stress. Hardness test of films also confirmed that more N content is with less hardness.  相似文献   

18.
椭偏透射法测量氢化非晶硅薄膜厚度和光学参数   总被引:1,自引:0,他引:1       下载免费PDF全文
针对多角度椭偏测量透明基片上薄膜厚度和光学参数时基片背面非相干反射光的影响问题,报道了利用椭偏透射谱测量等离子增强化学气相沉积法(PECVD)制备的a-Si:H薄膜厚度和光学参数的方法,分析了基片温度Ts和辉光放电前气体温度Tg的影响.研究表明,用椭偏透射法测量的a-Si:H薄膜厚度值与扫描电镜(SEM)测得的值相当,推导得到的光学参数与其他研究者得到的结果一致.该方法可用于生长在透明基片上的其他非晶或多晶薄膜. 关键词: 椭偏测量 透射法 光学参数 氢化非晶硅薄膜  相似文献   

19.
《Current Applied Physics》2014,14(12):1845-1848
Nitrogen-doped amorphous carbon thin films (a-CNx) were prepared on silicon substrate by pulsed laser deposition process using methane (CH4) and nitrogen (N2) as source gas. The electrical properties of a-CNx films changes with nitrogen concentration in the film structure. The intensity ratio of the D and G peak (ID/IG) increases with higher nitrogen concentration, which means that sp2-clusters were formed in these films and is responsible for the enhancement of conductivity of the a-CNx films. We observed that the amorphous carbon (a-C) films becoming more graphitic in nature yielding higher conductivity/lower resistivity with increase of nitrogen concentration. Electron field emission result shows that the emission current density enhances with nitrogen doping that indicates the useful in electron field emission devices application.  相似文献   

20.
彭少麒  刘国洪 《物理学报》1988,37(7):1209-1212
本文利用热释氢和红外吸收研究了H在非晶态碳(a-C:H)膜中的含量和组态。实验结果表明,随着样品制备时衬底温度的增大:1)H在a-C:H膜中的组态从两相结构过渡为单相结构;2)H在a-C:H膜中的含量单调减少;3)a-C:H膜中sP3/sP2键合比例单调增大。 关键词:  相似文献   

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