金刚石薄膜的结构特征对薄膜附着性能的影响

在不同实验条件下，用微波等离子体化学气相沉积设备在硬质合金(WC+6%Co)衬底上沉积了 具有不同结构特征的金刚石薄膜.用Raman谱表征薄膜的品质和应力，用压痕实验表征薄膜的 附着性能，考察了薄膜中sp²杂化碳含量、形核密度、薄膜厚度对薄膜附着性能 的影响.结 果表明：sp²杂化碳的缓冲作用使薄膜中sp²杂化碳的含量对薄膜中 残余应力有较大的影 响，从而使薄膜压痕开裂直径统计性地随sp²杂化碳含量的增加而减小；仅仅依 靠超声遗 留的金刚石晶籽提高形核密度并不能有效改变薄膜与硬质合金基体之间的化学结合状况，从 而不能有效提高薄膜在衬底上的附着性能；在薄膜较薄时，晶粒之间没有压应力的存在，开 裂直径并不明显随厚度增加而增加，只有当薄膜厚度增加到一定值，晶粒之间才有较强压应 力存在，开裂直径随厚度的增加而较为迅速地增加. 关键词： 金刚石薄膜 附着性能 2杂化碳')" href="#">sp²杂化碳 成核密度 薄膜厚度     

Investigation of properties of Cu containing DLC films produced by PECVD process

Copper containing diamond like carbon (Cu-DLC) thin films were deposited on various substrates at a base pressure of 1×10^?3 Torr using a hybrid system involving DC-sputtering and radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) techniques. The compressive residual stresses of these films were found to be considerably lower, varying between 0.7 and 0.94 GPa and Cu incorporation in these films improve their conductivity significantly. Their structural properties were studied by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction techniques that clearly revealed the presence of Cu in the DLC structure. Raman analysis yields that Cu incorporation in DLC enhances the graphite-like sp² bonding. However, the sp² bonding was found to continuously reduce with the increasing C₂H₂ gas pressure, this may be due to reduction of Cu nanocrystal at the higher pressure. FTIR results inferred various bonding states of carbon with carbon, hydrogen and oxygen. In addition, hydrogen content and sp³ and sp² fractions in different Cu-DLC films were also estimated by FTIR spectra and were correlated with stress, electrical, optical and nano-mechanical properties of Cu-DLC films. The effect of indentation load (4–10 mN) on nano-mechanical properties of these films was also explored.     

掺杂CVD金刚石薄膜的应力分析

在不同实验条件下，用微波等离子体化学气相沉积(MPCVD)技术在Si基体上制备了S掺杂和B-S共掺杂CVD金刚石薄膜，利用X射线衍射仪和拉曼光谱仪研究掺杂对CVD金刚石薄膜的应力影响.研究结果发现，随着S掺杂浓度的增加，薄膜中sp²杂化碳含量和缺陷增多，CVD金刚石薄膜压应力增加；小尺寸的B原子与大尺寸的S原子共掺杂时，微量B的加入改变了CVD金刚石薄膜的应力状态，共掺杂形成B-S复合体进入金刚石晶体后降低金刚石晶体的晶格畸变程度，减少S原子在晶界上偏聚数量和晶体中非金刚石结构相含量，降低由于杂质、缺陷及sp²杂化碳含量产生的晶格畸变和薄膜压应力，提高晶格完整性. 关键词： 金刚石薄膜 掺杂 应力     

Effect of titanium incorporation on the structural, mechanical and biocompatible properties of DLC thin films prepared by reactive-biased target ion beam deposition method

Amorphous diamond like carbon (DLC) and titanium incorporated diamond like carbon (Ti-DLC) thin films were deposited by using reactive-biased target ion beam deposition method. The effects of Ti incorporation and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy and nano-indentation. It was found that the Ti content in Ti-DLC films gets increased with increasing target bias voltage. At about 4.2 at.% of Ti, uniform sized well dispersed nanocrystals were seen in the DLC matrix. Using FFT analysis, a facility available in the TEM, it was found that the nanocrystals are in cubic TiC phase. Though at the core, the incorporated Ti atoms react with carbon to form cubic TiC; most of the surface exposed Ti atoms were found to react with the atmospheric oxygen to form weakly bonded Ti-O. The presence of TiC nanocrystals greatly modified the sp³/sp² hybridized bonding ratio and is reflected in mechanical hardness of Ti-DLC films. These films were then tested for their biocompatibility by an invitro cell culturing test. Morphological observation and the cell proliferation test have demonstrated that the human osteoblast cells well attach and proliferate on the surface of Ti incorporated DLC films, suggesting possible applications in bone related implant coatings.     

Synthesis and Characterization of Some Carbon Based Nanostructures

Carbon thin films were synthesized using the original Thermionic Vacuum Arc (TVA) method. Mechanical properties were investigated using Micro Materials NanoTest 500 instrument using a NT Berkovich indenter. XPS provides a quantitative analysis of the surface composition and X‐ray generated Auger electron spectroscopy (XAES) performed by Thermoelectron ESCALAB 250 revealed information about the sp³:sp² ratio of the carbon bondings. Structure and morphology was studied by Transmission Electron Microscope CM120ST, providing information on the grain size distribution of the crystalline diamond structures (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrochemical properties of undoped CVD diamond films

The electrochemical properties of undoped diamond polycrystalline films grown on tungsten wire substrates using methanol as a precursor are described. The diamond film quality was changed by introducing sp²-bonded non-diamond carbon impurity through adjustment of the methanol-to-hydrogen (C/H) source gas ratio used for diamond growth.The electrodes were characterized by Raman spectroscopy, scanning electronic microscopy (SEM) and cyclic voltammetry (CV).Diamond coated tungsten wires were then used as a working electrode to ascertain their electrochemical behavior in electrolytic medium. Electrochemical windows of these films were found to be suitable in the potential range of [−2.5 V, +2.2 V] vs. Ag/AgCl in acid medium (0.1 M KCl).The electrochemical behavior was evaluated also using the Fe(CN)₆^3−/4−redox couple.The results demonstrate that the grain boundaries and sp²-hybridized carbon impurity can have a significant influence on electrochemical window of undoped diamond electrodes. It was observed that with increasing sp² carbon impurity concentration the electrochemical window decreases.     

Effect of nickel on the structure and bond type in amorphous diamond-like carbon films

Experimental data are presented from studies of the structure and bond type of carbon atoms in amorphous carbon-nickel films deposited from pulsed vacuum-arc discharge plasma sources. X-ray photoelectron spectroscopy was used. The characteristics of the plasmon loss spectra depend significantly on the deposition parameters. Carbon exists in a mixed sp²+sp³ hybridized state in the carbon–nickel films. The ratio of sp³/sp² carbon bonds increases when the nickel content is reduced (from 5.5 to 1.0 atomic %) and the deposition angle is increased. The structure closest to that of diamond was with a substrate bias voltage of –80 to –100 V and a deposition angle of 90°.     

Correlation between substrate bias, growth process and structural properties of phosphorus incorporated tetrahedral amorphous carbon films

We investigate the growth process and structural properties of phosphorus incorporated tetrahedral amorphous carbon (ta-C:P) films which are deposited at different substrate biases by filtered cathodic vacuum arc technique with PH₃ as the dopant source. The films are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, Raman spectroscopy, residual stress measurement, UV/VIS/NIR absorption spectroscopy and temperature-dependent conductivity measurement. The atomic fraction of phosphorus in the films as a function of substrate bias is obtained by XPS analysis. The optimum bias for phosphorus incorporation is about −80 V. Raman spectra show that the amorphous structures of all samples with atomic-scaled smooth surface are not remarkably changed when PH₃ is implanted, but some small graphitic crystallites are formed. Moreover, phosphorus impurities and higher-energetic impinging ions are favorable for the clustering of sp² sites dispersed in sp³ skeleton and increase the level of structural ordering for ta-C:P films, which further releases the compressive stress and enhances the conductivity of the films. Our analysis establishes an interrelationship between microstructure, stress state, electrical properties, and substrate bias, which helps to understand the deposition mechanism of ta-C:P films.     

Effects of hydrogen and oxygen on the electrochemical corrosion and wear-corrosion behavior of diamond films deposited by hot filament chemical vapor deposition

A diamond film was deposited on silicon substrate using hot filament chemical vapor deposition (HFCVD), and H₂ and O₂ gases were added to the deposition process for comparison. This work evaluates how adding H₂ and O₂ affects the corrosion and wear-corrosion resistance characteristics of diamond films deposited on silicon substrate. The type of atomic bonding, structure, and surface morphologies of various diamond films were analyzed by Raman spectrometry, X-ray diffraction (XRD) and atomic force microscopy (AFM). Additionally, the mechanical characteristics of diamond films were studied using a precision nano-indentation test instrument. The corrosion and wear-corrosion resistance of diamond films were studied in 1 M H₂SO₄ + 1 M NaCl solution by electrochemical polarization. The experimental results show that the diamond film with added H₂ had a denser surface and a more obvious diamond phase with sp³ bonding than the as-deposited HFCVD diamond film, effectively increasing the hardness, improving the surface structure and thereby improving corrosion and wear-corrosion resistance properties. However, the diamond film with added O₂ had more sp² and fewer sp³ bonds than the as-deposited HFCVD diamond film, corresponding to reduced corrosion and wear-corrosion resistance.     

Thermal conductive performance of deposited amorphous carbon materials by molecular dynamics simulation

A series of diamond-like carbon (DLC) films with different microstructure were prepared by depositing carbon atoms on diamond surface with incident energy ranging from 1 to 100 eV. The thermal conductivity of the deposited films and the Kapitza resistance between the film and the diamond substrate were investigated. Results show that the average density, the average fraction of sp³ bonding and the thermal conductivity of the DLC films increase first, reaching a maximum around 20–40 eV before decreasing, while the Kapitza resistance decreases gradually with increased deposition energy. The analysis suggests that the thermal resistance of the interface layer is in the order of 10^?10 m²K/W, which is not ignorable when measuring the thermal conductivity of the deposited film especially when the thickness of the DLC film is not large enough. The fraction of sp³ bonding in the DLC film decreases gradually normal to the diamond surface. However, the thermal conductivity of the film in normal direction is not affected obviously by this kind of structural variation but depends linearly on the average fraction of sp³ bonding in the entire film. The dependence of the thermal conductivity on the fraction of sp³ bonding was analysed by the phonon theory.     

Study of diamond film by dynamic nuclear polarization-enhanced13C nuclear magnetic resonance spectroscopy

Three chemical vapor deposited diamond films were studied by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state¹³C nuclear magnetic resonance (NMR) spectroscopy. Enhanced¹³C direct-polarization spectra of diamond films were obtained by irradiating the samples with microwaves at or near electron spin resonance Larmor frequency of carbon center free radicals. No NMR signal for sp² hybridized carbons could be observed. From the curve of the DNP enhancement as a function of frequency, it is found that the dominant DNP mechanism is the solid-state effect. The¹³C cross-polarization spectrum, which is an evidence for existence of the proton defect in the lattice of diamond films, is much broader than the¹³C single pulse spectrum. The reason is discussed shortly.     

含氮氟化类金刚石(FN-DLC)薄膜的研究：(Ⅰ) sp结构与化学键分析

以CF₄，CH₄和N₂为源气体，利用射频等离子体增强化学气相沉积法，在不同功率下制备了含氮氟化类金刚石膜.用俄歇电子能谱、拉曼光谱、X射线光电子能谱和傅里叶变换红外光谱对薄膜的电子结构和化学键进行了表征，并结合高斯分峰拟合方法分析了薄膜中sp²，sp³结构比率.结果表明，制备的薄膜属于类金刚石结构，不同沉积功率下，薄膜内的sp²/sp³值在2.0—9.0之间，随着沉积功率的增加薄膜内sp²的相对含量增加.膜内主要有C—F_x(x=1，2)，C—C，C=C和C≡N等化学键.沉积功率增加，C—C基团增加，膜内F的浓度降低，C—F基团减少，薄膜的关联加强，稳定性提高. 关键词： 含氮氟化类金刚石膜 sp结构 化学键结构 射频功率     

Structural,optical and electrical properties of sulfur-incorporated amorphous carbon films

Amorphous carbon–sulfur (a-C:S) composite films were prepared by vapor phase pyrolysis technique. The structural changes in the a-C:S films were investigated by electron microscopy. A powder X-ray diffraction (XRD) study depicts the two-phase nature of a sulfur-incorporated a-C system. The optical bandgap energy shows a decreasing trend with an increase in the sulfur content and preparation temperature. This infers a sulfur incorporation and pyrolysis temperature induced reduction in structural disorder or increase in sp ² or π-sites. The presence of sulfur (S 2p) in the a-C:S sample is analyzed by the X-ray photoelectron spectroscopy (XPS). The sp ³/sp ² hybridization ratio is determined by using the XPS C 1s peak fitting, and the results confirm an increase in sp ² hybrids with sulfur addition to a-C. The electrical resistivity variation in the films depends on both the sulfur concentration and the pyrolysis temperature.     

Synthesis of carbon nitride films by direct current plasma assisted pulsed laser deposition

Carbon nitride films were deposited by pulsed laser ablation of a graphite target under a nitrogen atmosphere at room temperature. A direct current discharge apparatus was used to supply active nitrogen species during the deposition of carbon nitride films. The composition and bonding structure of carbon nitride films were determined by Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy. The incorporation of nitrogen atoms in the films is greatly improved by the using of a dc glow discharge. The ratio N/C can reach 0.34 at the discharge voltage of 400 V. Six peaks centered at 1025 cm^-1, 1226 cm^-1, 1381 cm^-1, 1534 cm^-1, 1629 cm^-1, and 2200 cm^-1 can be clearly distinguished from the FTIR spectra of the deposited films, which indicates the existence of C–N, C=N, and C≡N bonds. The fraction of sp² C, C≡N bonds, and C=N bonds in the deposited films increases with increasing discharge voltage. Deconvolution results of C 1s and N 1s spectra also indicate that nitrogen atoms in the films are chemically bonded to sp¹ C, sp² C, and sp³ C atoms. Most of the nitrogen atoms are bonded to sp² C atoms. Increasing the discharge voltage leads to a decrease of the fraction of nitrogen atoms bonded to sp² C and the fraction of amorphous carbon; however, it leads to an increase of the fraction of nitrogen atoms bonded to sp³ C and the fraction of sp² C and sp³ C atoms bonded to nitrogen atoms. Received: 7 June 2000 / Accepted: 19 February 2001 / Published online: 27 June 2001     

Low voltage electrodeposition of CNx films and study of the effect of the deposition voltage on bonding configurations

Carbon nitride (CN_x) films were deposited from acetonitrile at low voltage (150-450 V) through electrodeposition. The films were characterized by atomic force microscopy (AFM), Raman spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. AFM investigations revealed that the grain size was ∼200 nm and roughness was ∼10 nm. The films were found to be continuous and close packed. IR spectra revealed existence of strong sp³, sp² type bonding and weak sp type carbon nitrogen bonds and these bonds were found to increase with voltage. The fraction of sp³-bonded species in the sample increased in low voltage range and after reaching maximum at 350 V, decreased for higher voltages. However, the concentration of sp² CN ring structures in the film increased with increasing voltage. Also, the peak width decreased at low voltages reaching a minimum and increased thereafter. It was observed that the voltage dependent increase in the concentration of polymeric type sp² CN (chain) structures was much more pronounced than that of graphitic type sp² CN (ring) structures. Raman spectra showed the presence of both the D and G bands. The shift in the G band indicated the presence of nitrogen in the film. The I_D/I_G ratio was found to increase with the incorporation of nitrogen. Auger electron spectroscopy (AES) showed a clear increase in the nitrogen content with increase in the voltage. The formation of the film could be explained on the basis of dissociation of electrolyte under applied voltage.     

Field emission from nitrogen-implanted CVD diamond film grown on silicon wafer

Nitrogen was implanted into chemical vapor deposition (CVD) diamond films and the electron field emission properties of the nitrogenated diamond films were investigated. Nitrogen implantation was carried out using 10 keV in the dose range from 1×10¹⁶ to 5×10¹⁷ cm^-2 at room temperature. Raman and X-ray photoelectron spectroscopy measurements revealed that nitrogen implantation damaged the structure of the diamond film and promoted the formation of sp² C–C and sp² C–N bondings. Increasing the implantation dose could lower the threshold field of the emission of the diamond film from 18 V/m to 4 V/m. The effective work function of the nitrogen-implanted CVD diamond films was estimated to be in the range of 0.01–0.1 eV. The enhancement of field emission for nitrogen-implanted CVD diamond films was attributed to the increase of the sp² C bonds fraction and the formation of defect bands within the bulk diamond band gap induced by nitrogen implantation, which could alter the work function and elevate the Fermi level. Consequently, the energy barrier for electron tunneling was reduced.     

Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature

A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 C to 1350 C.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp 3-CH 2-symmetric(2850 cm-1) and sp 3 CH 2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the sp 3 C-H bond is rather stable in diamond crystals.     

Low voltage electrodeposition of diamond like carbon (DLC)

Attempt has been made to deposit diamond like carbon (DLC) films from ethanol through electrodeposition at low voltages (80-300 V) at 1 mm interelectrode separation. The films were characterized by atomic force microscopy (AFM), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and Auger electron Spectroscopy (AES). AFM investigations revealed the grain sizes are of tens of nanometers. The films were found to be continuous, smooth and close packed. Presence of peaks at 2958, 2929 and 2869 cm⁻¹ in FTIR spectrum indicates the bonding states to be of predominantly sp³ type (C-H). Raman spectroscopy analysis revealed two broad bands at ∼1350 and ∼1570 cm⁻¹. The downshift of the G-band of graphite is indicative of presence of DLC. Analysis of the Raman spectra for the samples revealed an improvement in the film quality with increase in the voltage. Micro Raman investigations indicate the formation of diamond phase at the deposition potential of 80 V. The sp² contents the films calculated from Auger electron spectra were calculated and were found to be 31, 19 and 7.8% for the samples prepared at 80, 150 and 300 V, respectively. A tentative mechanism for the formation of DLC has been proposed. These results indicate the possibility of deposition of DLC at low voltage.     

Mechanical properties and platelet adhesion behavior of diamond-like carbon films synthesized by pulsed vacuum arc plasma deposition

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 I_D/I_G 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.     

化学气相沉积法制备金刚石膜截面微区Raman分析

采用微区Raman散射分析方法研究化学气相沉积法制备的金刚石膜的横截面.金刚石膜从衬底面到生长面不同位置具有不同特征的Raman谱,依此对膜中的金刚石、石墨和非晶碳成分进行分析.衬底面附近区域对应金刚石膜生长过程的成核阶段,非晶碳成分含量较高,相应于1200—1600cm^-1波段较大的散射强度和存在较强的荧光背底.膜厚增大,非晶碳成分中sp³结构成分首先减少,而sp²结构成分和石墨成分的减少相对缓慢.而生长面附近区域只有比较单纯的晶体金刚石 关键词：