Effect of Gas Sources on the Deposition of Nano-Crystalline Diamond Films Prepared by Microwave Plasma Enhanced Chemical Vapor Deposition

Nano-crystalline diamond (NCD) films were deposited on silicon substrates by a microwave plasma enhanced chemical vapor deposition (MPCVD) reactor in C2H5OH/H2 and CH4/H2/O2 systems, respectively, with a constant ratio of carbon/hydrogen/oxygen. By means of atomic force microscopy (AFM) and X-ray diffraction (XRD), it was shown that the NCD films deposited in the C2H5OH/H2 system possesses more uniform surface than that deposited in the CH4/H2/O2 system. Results from micro-Raman spectroscopy revealed that the quality of the NCD films was different even though the plasmas in the two systems contain exactly the same proportion of elements. In order to explain this phenomenon, the bond energy of forming OH groups, energy distraction in plasma and the deposition process of NCD films were studied. The experimental results and discussion indicate that for a same ratio of carbon/hydrogen/oxygen, the C2H5OH/H2 plasma was beneficial to deposit high quality NCD films with smaller average grain size and lower surface roughness.     

Improvement on Diamond Nucleation Treated by Pulsed Arc Discharge Plasma

A technique of improvement on diamond nucleation based on pulsed arc discharge plasma at atmospheric pressure was developed. The pulsed arc discharge was induced respectively by nitrogen, argon and methanol gas. After the arc plasma pretreatment, a nucleation density higher than 10^10 cm^-2 may be obtained subsequently in chemical vapor deposition (CVD) on a mirror-polished silicon substrate without any other mechanical treatment. The effects of the arc discharge plasma on the diamond nucleation were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR) and Raman spectroscopy. The enhancement of nucleation is postulated to be a result of the formation of carbonlike phase materials or nitrogenation on the substrate surface without surface defect produced by arc discharge.     

Microwave Plasma Chemical Vapor Deposition of Diamond Films on Silicon From Ethanol and Hydrogen

Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition(MPCVD)from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450℃.The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy(SEM).The microstructure and the phase of the film have been characterized using Raman spectroscopy and X-ray diffraction(XRD).The diamond nucleation density significantly decreases with the increasing of the substrate temperature.There are only sparse nuclei when the substrate temperature is higher than 800℃ although the ethanol concentration in hydrogen is very high.That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450℃ extends into broadban indicates that the film is of nanophase.No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP^3 carbon.The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.     

Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

Boron-doped nanocrystalline diamond(NCD) exhibits extraordinary mechanical properties and chemical stability,making it highly suitable for biomedical applications.For implant materials,the impact of boron-doped NCD films on the character of cell growth(i.e.,adhesion,proliferation) is very important.Boron-doped NCD films with resistivity of 10~(-2)Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition(MPCVD) process with H_2 bubbled B_2O_3.The crystal structure,diamond character,surface morphology,and surface roughness of the boron-doped NCD films were analyzed using different characterization methods,such as X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and atomic force microscopy(AFM).The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope(SKFM).The cytotoxicity of films was studied by in vitro tests,including fluorescence microscopy,SEM and MTT assay.Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates.MG-63 cells adhered well and exhibited a significant growth on the surface of films,suggesting that the boron-doped NCD films were non-toxic to cells.     

Characterization of Thin Films Deposited with Precursor Ferrocene by Plasma Enhanced Chemical Vapour Deposition

In this paper, the characterization of thin films, deposited with the precursor ferrocene （FcH） by the plasma enhanced chemical vapour deposition （PECVD） technique, was investigated. The films were measured by Scanning Electronic Microscopy （SEM）, Atomic Force Microscopy （AFM）, Electron Spectroscopy for Chemical Analysis （ESCA）, and Superconducting Quantum Interference Device （SQUID）. It was observed that the film＇s layer is homogeneous in thickness and has a dense morphology without cracks. The surface roughness is about 36 nm. From the results of ESCA, it can be inferred that the film mainly contains the compound FeOOH, and carbon is combined with oxygen in different forms under different supply-powers. The hysteresis loops indicate that the film is of soft magnetism.     

Monte Carlo Simulation of Electron Swarm in the Diamond Film Growth via EACVD

Monte Carlo simulations are adopted to study the electron transport porcess in the non-uniform electric field.Some important parameters of electrons in diamond films dynamic process at low temperature via EACVD such as angle distribution,energy distribution,average energy of electrons are given.The results indicate that the electron scattering near the substrate is mainly of a large-angle scattering,exhibiting a double-peaking distribution .All of the conclusions provide some theoretical data referential to the vapor dynamic model of diamond film growth at low temperature via EACVD.     

Characterization of Diamond: Like Carbon Films Synthesized by DC-Plasma Enhanced Chemical Vapor Deposition

In this paper, diamond-like carbons were produced on tungsten and aluminum substrates by DC plasma enhanced chemical vapor deposition (DC-PECVD) system in a C₂H₂/H₂ gas mixture using C₂H₂ as source hydrocarbon and H₂ as etching and diluting gas. The operation pressure during the growth and substrates temperature were 15 Torr and 180°C, respectively. Characterization of the DLCs deposited on tungsten and aluminum substrates were carried out by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Raman spectroscopy and Atomic force microscopy (AFM). AFM analysis displayed that the DLCs grown on W substrate has lower roughness than the DLCs deposited on Al substrate and it was smoother. FTIR analysis indicates the existence of C–H vibration mode in the DLCs grown on both of substrates. The Raman spectroscopy shows G peak position and I(D)/I (G) ratio decreased for the DLCs grown on W substrate. The SEM images show diffuse and dense distribution of DLCs in Al and W substrate, respectively. These results shows that the optimum conditions were obtained on W substrate.     

Growth of Free-Standing Diamond Films on Stainless Steel

Free-standing diamond films have been successfully deposited on stainless steel substrates using microwave plasma-assisted chemical vapor deposition. Although iron, which is the main element of stainless steel, is known to inhibit the nucleation of diamond and enhance the formation of graphite, we were able to grow relatively thick films （-1.2 mm）. The films were easily detachable from the substrates. The poor adhesion made it possible to obtain free-standing diamond films without chemical etching. Raman spectroscopy showed the 1332 cm^-1 characteristic Raman peak of diamond and the 1580 cm^-1, 1350 cm^-1 bands of graphite on the growth surface and backside of the films, respectively. By energy dispersive X-ray spectroscopy it was only possible to detect iron on the back of the films, but not on the surface. The role of iron in the film growth is discussed.     

Effects of Surface Pretreatment on Nucleation and Growth of Ultra-Nanocrystalline Diamond Films

The effects of different surface pretreatment methods on the nucleation and growth of ultra-nanocrystalline diamond(UNCD) films grown from focused microwave Ar/CH_4/H_2(argonrich) plasma were systematically studied.The surface roughness,nucleation density,microstructure,and crystallinity of the obtained UNCD films were characterized by atomic force microscope(AFM),scanning electron microscopy(SEM),X-ray diffraction(XRD),and Raman spectroscopy.The results indicate that the nucleation enhancement was found to be sensitive to the different surface pretreatment methods,and a higher initial nucleation density leads to highly smooth UNCD films.When the silicon substrate was pretreated by a two-step method,i.e.,plasma treatment followed by ultrasonic vibration with diamond nanopowder,the grain size of the UNCD films was greatly decreased:about 7.5 nm can be achieved.In addition,the grain size of UNCD films depends on the substrate pretreatment methods and roughness,which indicates that the surface of substrate profile has a "genetic characteristic".     

Sheet Resistance and Gas-Sensing Properties of Tin Oxide ThinFilms by Plasma Enhanced Chemical Vapor Deposition＊

Tin oxide (SnO2) thin films are prepared at different temperatures by plasmaenhanced chemical vapor deposition (PECVD). The structural characterizations of the films are investigated by various analysis techniques. X-ray diffraction patterns (XRD) show that the phase of SnO2 films are different at different deposition temperatures. The sheet resistance of the films decreases with increase of deposition temperature. X-ray photoelectron spectroscopy (XPS) shows that the SnO2 thin film is non-stoichiometric. The sheet resistance increases with increase in oxygen flow. Sb-doped SnO2 thin films are more sensitive to alcohol than carbon monoxide, and its maximum sensitivity is about 220％.     

Monte Carlo Simulation of Electron Velocity Distribution and Gas Phase Process in Electron-Assisted Chemical Vapor Deposition

The gas phase process of diamond film deposition from CH4/H2 gas mixture by electron-assisted chemical vapor deposition is simulated by the Monte-Carlo method. The electron velocity distribution under different E/P (the ratio of the electric field to gas pressure) is obtained, and the velocity profile is asymmetric. The variation of the number density of CH3 and H with different CH4 concentrations and gas pressure is investigated, and the optimal experimental parameters are obtained: the gas pressure is in the range of 2.5 kPa ~ 15 kPa and the CH4 concentration is in the range of 0.5% ~ 1%. The energy carried by the fragment CH3 as the function of the experiment parameters is investigated to explain the diamond growth at low temperature. These results will be helpful to the selection of optimum experimental conditions for high quality diamond films deposition in EACVD and the modeling of plasma chemical vapor deposition.     

A Study of Diamond-Like Carbon Thin Films Prepared by Microwave Plasma Chemical Vapour Deposition

In order to deposit good films, we need to study the uniformity of plasma density and the plasma density under different gas pressures and powers. The plasma density was diagnosed by a Langmuir probe. The optical emission spectroscopy （OES） of CH4 and H2 discharge was obtained with raster spectroscopy, with characteristic peaks of H and CH achieved. Diamond-like carbon films were achieved based on the study of plasma density and OES and characterized by atomic force microscope （AFM）, X-ray diffraction instrument （XRD）, Raman spectroscope and profiler.     

Effect of Radio-Frequency and Low-Frequency Bias Voltage on the Formation of Amorphous Carbon Films Deposited by Plasma Enhanced Chemical Vapor Deposition

The effect of radio-frequency （RF） or low-frequency （LF） bias voltage on the for- mation of amorphous hydrogenated carbon （a-C：H） films was studied on silicon substrates with a low methane （CH4） concentration （2-10 vol.%） in CH4＋Ar mixtures. The bias substrate was applied either by RF （13.56 MHz） or by LF （150 kHz） power supply. The highest hardness values （~18-22 GPa） with lower hydrogen content in the fihns （~20 at.%） deposited at 10 vol.% CH4, was achieved by using the RF bias, However, the films deposited using the LF bias, under similar RF plasma generation power and CH4 concentration （50 W and 10 vol.%, respectively）, displayed lower hardness （~6-12 GPa） with high hydrogen content （~40 at.%）. The structures analyzed by Fourier Transform Infrared （FTIR） and Raman scattering measurements provide an indication of trans-polyacetylene structure formation. However, its excessive formation in the films deposited by the LF bias method is consistent with its higher bonded hydrogen concentration and low level of hardness, as compared to the film prepared by the RF bias method. It was found that the effect of RF bias on the film structure and properties is stronger than the effect of the low-frequency （LF） bias under identical radio-frequency （RF） powered electrode and identical PECVD （plasma enhanced chemical vapor deposition） system configuration.     

Fabrication of Diamond Microstructures by Using Dry and Wet Etching Methods

Diamond films have great potential for micro-electro-mechanical system(MEMS) application.For device realization,precise patterning of diamond films at micrometer scale is indispensable.In this paper,simple and facile methods will be demonstrated for smart patterning of diamond films,in which two etching techniques,i.e.,plasma dry etching and chemical wet etching(including isotropic-etching and anisotropic-etching) have been developed for obtaining diamond microstructures with different morphology demands.Free-standing diamond micro-gears and micro-combs were achieved as examples by using the experimental procedures.It is confirmed that as-designed diamond structures with a straight side wall and a distinct boundary can be fabricated effectively and efficiently by using such methods.     

脉冲激光和重离子辐照FPGA产生的多位翻转效应的比较

以SRAM型FPGA为试验对象,研究脉冲激光模拟重离子产生单粒子多位翻转效应的可行性。FPGA的多位翻转依据其物理位置关系的不同分为3种类型:同帧同字节、同帧相邻字节和相邻帧。针对Virtex-ⅡFPGA分别进行脉冲激光与重离子的单粒子多位翻转效应的测试,对比脉冲激光和重离子在Virtex-ⅡFPGA产生多位翻转的类型、多位翻转的物理位置关系。结果表明,脉冲激光触发的Virtex-ⅡFPGA的多位翻转物理位置关系与重离子相同,对比脉冲激光与重离子的饱和翻转截面发现,应用脉冲激光和重离子得到的Virtex-Ⅱ饱和翻转截面基本一致,表明脉冲激光可模拟重离子研究Virtex-ⅡFPGA的多位翻转效应。     

Characterization of Crystalline Nanoparticles/Nanorods Synthesized by Atmospheric Plasma Enhanced Chemical Vapor Deposition of Perfluorohexane

A mass of nanoparticles/nanorods were formed on a simultaneously deposited gran- ular film by plasma enhanced chemical vapor deposition （PECVD） of perfluorohexane at atmo- spheric pressure without any catalysts or templates. Scanning electron microscopy （SEM） and X-ray photoelectron spectroscopy （XPS） were used to characterize the morphology and the chem- ical compositions of nanoparticles. The average size of particles is about 100 nm and the length of synthesized nanorods is between 1 μm and 2.5/tm. The analyses of transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, selected area electron diffraction（SAED） and X-ray diffraction （XRD） reveals that the nanoparticles and nanorods are crystalline.     

Incorporation of Nitrogen into Amorphous Carbon Films Produced by Surface-Wave Plasma Chemical Vapor Deposition

In order to study the influence of nitrogen incorporated into amorphous carbon films, nitrogenated amorphous carbon films have been deposited by using surface wave plasma chemical vapor deposition under various ratios of N2/CH4 gas flow. Optical emission spectroscopy has been used to monitor plasma features near the deposition zone. After deposition, the samples are checked by Raman spectroscopy and x-ray photo spectroscopy (XPS). Optical emission intensities of CH and N atom in the plasma are found to be enhanced with the increase in the N2/CH4 gas flow ratio, and then reach their maximums when the N2/CH4 gas flow ratio is 5%. A contrary variation is found in Raman spectra of deposited films. The intensity ratio of the D band to the G band (ID/IG) and the peak positions of the G and D bands all reach their minimums when the N2/CH4 gas flow ratio is 5%. These show that the structure of amorphous carbon films has been significantly modified by introduction of nitrogen。     

The Study of Active Atoms in High-Voltage Pulsed Coronal Discharge by Optical Diagnostics

In this study, the emission spectra of active atoms O (3p^5p → 3s^5S^02 777.4 nm),Ha (3P→2S 656.3 nm) and N (3p^4P→ 3s^4S^0 742.3 nm, 744.2 nm, 746.8 nm) produced by thepositive high-voltage pulsed corona discharge (HVPCD) of N2 and H2O mixture in a needle-plate reactor have successfully been recorded against a severe electromagnetic interference coming from the HVPCD at one atmosphere. The effects of the peak voltage, the repetition rate of pulsed discharge and the flow rate of oxygen on the production of those active atoms are investigated. It is found that when the peak voltage and the repetition rate of the pulsed discharge are increased,the emission intensities of those active atoms rise correspondingly. And the emission intensities of O (3p^5P→3s^5S^0 777.4 nm), Hα (3P→2S 656.3 nm) and N (3p^4P→3s^4S^0 742.3 nm, 744.2 nm,746.8 nm) increase with the flow rate of oxygen (from 0 to 25 ml/min) and achieve a maximum value at a flow rate of 25 ml/min. When the flow rate of oxygen is increased further, the emission intensities of those atoms visibly decrease correspondingly. The main physicochemical processes of interaction involved between electrons, neutrals and ions are also discussed.     

Plasma-Assisted Chemical Vapor Deposition of Titanium Oxide Films by Dielectric Barrier Discharge in TiCl_4/O_2/N_2 Gas Mixtures

Low-pressure dielectric barrier discharge（DBD） TiCl4/O2and N2 plasmas have been used to deposit titanium oxide films at different power supply driving frequencies. A homemade large area low pressure DBD reactor was applied, characterized by the simplicity of the experimental set-up and a low consumption of feed gas and electric power, as well as being easy to operate. Atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy,and contact angle measurements have been used to characterize the deposited films. Experimental results show all deposited films are uniform and hydrophilic with a contact angle of about 15 o.Compared to titanium oxide films deposited in TiCl4/O2gas mixtures, those in TiCl4/O2/N2gas mixtures are much more stable. The contact angle of titanium oxide films in TiCl4/O2/N2gas mixtures with the addition of 50% N2 and 20% TiCl4 is still smaller than 20 o, while that of undoped titanium oxide films is larger than 64 owhen they are measured after one week. The low-pressure TiCl4/O2plasmas consist of pulsed glow-like discharges with peak widths of several microseconds, which leads to the uniform deposition of titanium oxide films. Increasing a film thickness over several hundreds of nm leads to the film’s fragmentation due to the over-high film stress. Optical emission spectra（OES） of TiCl4/O2DBD plasmas at various power supply driving frequencies are presented.     

Inactivation of Bacteria in Oil Field Injected Water by a Pulsed Plasma Discharge Process

Pulsed plasma discharge was employed to inactivate bacteria in the injection water for an oil field.The effects of water conductivity and initial concentration of bacteria on elimination efficiency were investigated in the batch and continuous flow modes.It was demonstrated that Fe~(2+) contained in injection water could enhance the elimination efficiency greatly.The addition of reducing agent glutathione(GSH) indicated that active radicals generated by pulsed plasma discharges played an important role in the inactivation of bacteria.Moreover,it was found that the microbial inactivation process for both batch and continuous flow mode well fitted the model based on the Weibull's survival function.