Effect of Plasma Boronitriding on Diamond Nucleation and Growth onto Cemented Carbide Substrates

Plasma boronitriding has been successfully employed to overcome the difficulty in diamond growth on ferrous-based substrates,Commercial cobalt-sintered,tungsten-cemented carbides(WC (Co) were pretreated by a plasma boronitriding method,diamond was then deposited by microwave-enhanced chemical vapor deposition (MPCVD) ,The deposited films were characterized by scanning electron microsopy and Raman spectroscopy,Conitinuous diamond films with a sharp characteristic Raman Peak of 1334 cm^-1 were grown and adhered well on the boronitrided region of the cemented carbide substrates,On,the other hand,a mixture of diamond crystallites,amorphous carbon and graphitic carbon was loosely deposited on the unboronitrided region A cobalt inert thin layer formed after plasma bornitriding pretreatment enabled the subsequent nucleation and growht of a high-quality CVD iamond.     

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.     

Optical Characterization of Diamond Synthesis Using CH3OH-H2 Gas Mixtures

Diamond films with high infrared transmittance have been successfully deposited using CH3OH-H2 gas mixtures through microwave plasma enhanced chemical vapor deposition (MWCVD). The primary purpose of this study is to determine the effect of the deposition conditions on the optical properties of MWCVD diamond films using CH3OH-H2 gas mixtures. Room temperature optical properties of freestanding diamond films were studied by Fourier transform IR spectroscopy. Experimental results indicated that under appropriate deposition temperature (620 ℃) and methanol concentration (5.7%), the refractive index of CVD diamond films (2.33) was comparable with that of natural diamond (2.417). The average infrared transmittance was above 65% in the middle infrared region (500 cm^-1 - 4000 cm^-1), approaching to the theoretical value of diamond (71.4%). The mechanism of growing high IR transmittance diamond films by utilizing CH3OH-H2 gas system is that the high methanol concentration used in this study makes the surface roughness of diamond films decreased by increasing the secondary nucleation density and the high O/C ratio in CH3OH-H2 gas system, improved the quality of diamond films and therefore decreased the absorption of non-diamond carbon in the films.     

Thin relaxed SiGe layer grown on Ar^＋ ion implanted Si substrate by ultra-high vacuum chemical vapor deposition

1 Introduction Relaxed SiGe layers have gained considerable attention due to their applications in strained Si/SiGe high electron mobility transistor, metal-oxide-semi- conductor field-effect transistor (MOSFET) and other devices. High-quality relaxed SiGe templates, espe- cially those with low threading dislocation density and smooth surface, are crucial for the electrical perform- ance of devices.[1,2] In order to realize high-quality relaxed SiGe layer with such good characteristics, …     

Fundamental Studies on Acceleration of Charged Micro Particles (Macrons) and Its Interaction with Materials Surfaces by Implantation

Charged micro particles (macrons) of nickel or artificial diamond were implanted to the silver films evaporated on the silicon and polished stainless steel discs. Craters were formed on the materials by collisions of the macrons. The macrons are electrostatically charged on two planar electrodes at 30 kV, extracted through the central hole in one of the electrodes and accelerated at 100 kV to the target materials. The craters and the macrons were evenly distributed on the silver film to which nickel macrons had been implanted. Diamond macrons were stuck to the stainless steel and covered the surface. The velocity of a diamond macron of 1/4/μm in diameter was estimated to be 1 to 3km/s under an assumption that the charge of each macron is in the range 10³-10⁴e. The velocity is sufficient to cause not only plastic deformation, but impact damages such as craters for silver and stainless steel.     

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.     

Synthesis of Diamond Nanoplatelets/Carbon Nanowalls on Graphite Substrate by MPCVD

The films composed of carbon nanowalls and diamond nanoplatelets,respectively,can be simultaneously formed on graphite substrate by controlling the hydrogen etching rate during microwave plasma chemical vapor deposition.To modulate the etching rate,two kinds of substrate design were used:a bare graphite plate and a graphite groove covered with a single crystal diamond sheet.After deposition at 1200℃ for 3 hours,we find that dense diamond nanoplatelets were grown on the bare graphite,whereas carbon nanowalls were formed on the grooved surface,indicating that not only reaction temperature but also etching behavior is a key factor for nanostructure formation.     

Chemical state and distribution of iodine deposits on 17% Cr/12% Ni steel oxidised in CO2/CH3I gas mixtures

Iodine-131 is one of the most important volatile fission product elements with respect to radiobiological impact, and the characterisation of its chemical state and distribution on reactor surfaces is required for reactor safety assessments. To this end, duplicate samples of Type 316 (17%Cr/12% Ni) stainless steel oxidised in CO₂/CH₃I gas mixtures and previously characterised using X-ray photoelectron spectroscopy have been examined using Raman spectroscopy. The aim is to improve our understanding of the way in which iodine is distributed throughout the oxide scale and to identify its chemical state. In this paper we present Raman spectra recorded from a series of stainless steel specimens together with spectra recorded from a number of standard iodine compounds. It is demonstrated that the technique is well suited as a fingerprint method of species identification, can differentiate between the chemical state of iodine as iodide and iodate and can analyse thin oxide films (5–50 nm). Identification of iodine deposits in these oxide films at concentrations of 2 at% was not achieved however, there being insufficient iodine present to distinguish any peaks present from the background signal. It is concluded that local concentrations of iodine in oxide inclusions of different composition/morphology on the steel surface does not occur to any extent.     

Selective growth of diamond by hot filament CVD using patterned carbon film as mask

Selected-area deposition (SAD) of diamond films was achieved on silicon substrates with carbon film mask by hot filament chemical vapor deposition. Needle tip scraped lines were used to grow diamond films. Scanning electron microscope (SEM) investigation demonstrates that highly selective and sharp edged diamond films were produced. The results also demonstrate that the proper substrate temperature is very important for diamond selective growth in this deposition process. Since the enhancement of diamond growth was not observed on the needle tip scraped area of Si wafer with diamond powder scratching, the selective growth was considered to be closely correlated to silicon carbide formed during carbon film deposition and the residual carbon in the scraped area.     

加热去氩处理工艺对离子束混合沉积的C-SiC涂层阻氢性能的影响

利用Ar＋离子束混合技术在不锈钢基体上沉积C-SiC涂层，然后对部分样品进行加热去氩处理（400℃，30min），再用5keV氢离子源辐照样品。通过扫描电镜（SEM）的表面形貌观察、二次离子质谱仪（SIMS）的H与Ar元素深度分布和正离子质谱分析，研究去氩处理对氢离子辐照的C-SiC涂层的形貌和阻氢性能的影响。结果表明，经去氩处理，样品中不锈钢基体内的氢浓度降低了80%，显示出去氩处理的C-SiC涂层具有更高的阻氢性能。研究结果将为该技术应用于不锈钢基体上C-SiC涂层制备工艺的进一步改善提供依据。     

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.     

Highly （111）-textured diamond film growth with high nucleation density

In a traditional hot-filament chemical vapor deposition (HF-CVD) system, highly (111)-textured diamond film was deposited on Si (111) substrate treated by diamond powder ultrasonic scratching or other methods. The relationship between the (111)-textured diamond film growth and the nucleation density has been discussed. The morphologies and structures of the films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy.     

304NG在超临界水中的腐蚀增重随温度的异常关系

研究了奥氏体不锈钢304NG在550、600和650℃超临界水环境下的腐蚀行为。采用扫描显微镜、X射线能谱仪、X射线衍射仪分析了氧化膜的腐蚀形貌、组织结构和成分分布。实验结果表明,试样在3种不同温度下经1000h腐蚀实验后的增重均符合幂函数规律,但650℃时的腐蚀增重与600℃时的相比大幅下降,其主要原因为在较高温时,Cr的扩散速度快,试样表面氧化膜能够维持保护性从而使疖状腐蚀分布数量减少所致。     

Synthesis and Characteristics of Diamond-like Carbon Films Deposited on Quartz Substrate

Diamond-like carbon (DLC) fihns are deposited on quartz substrate using pure CH4 in the surface wave plasma equipment. A direct current negative bias up to -90 V is applied to the substrate to investigate the bias effect on the film characteristics. Deposited films are characterized by Raman spectroscopy, infrared (IR) and ultraviolet-visible absorption techniques. There are two broad Raman peaks around 1340 cm^-1 and 1600 cm^-1 and the first one has a greater sp^3 component with an increased bias. Infrared spectroscopy has three sp^3 C-H modes at 2852 cm^-1, 2926 cm^-1 and 2962 cm^-1, respectively and also shows an intensity increase with the negative bias. Optical band gap is calculated from the ultraviolet-visible absorption spectroscopy and the increased values with negative bias and deposition time are obtained. After a thermal anneal at about 500℃ for an hour to the film deposited under the bias of-90 V, we get an almost unchanged Raman spectrum and a peak intensity-reduced IR signal, which indicates a reduced H-content in the film. Meanwhile the optical band gap changed from 0.85 eV to 1.5 eV.     

Initial damage processes for diamond film exposure to hydrogen plasma

Diamond is considered to be a possible alternative to other carbon based materials as a plasma facing material in nuclear fusion devices due to its high thermal conductivity and resistance to chemical erosion. In this work CVD diamond films were exposed to hydrogen plasma in the MAGnetized Plasma Interaction Experiment (MAGPIE): a linear plasma device at the Australian National University which simulates plasma conditions relevant to nuclear fusion. Various negative sample stage biases of magnitude less than 500 V were applied to control the energies of impinging ions. Characterisation results from SEM, Raman spectroscopy and ERDA are presented. No measureable quantity of hydrogen retention was observed, this is either due to no incorporation of hydrogen into the diamond structure or due to initial incorporation as a hydrocarbon followed by subsequent etching back into the plasma. A model is presented for the initial stages of diamond erosion in fusion relevant hydrogen plasma that involves chemical erosion of non-diamond material from the surface by hydrogen radicals and damage to the subsurface region from energetic hydrogen ions. These results show that the initial damage processes in this plasma regime are comparable to previous studies of the fundamental processes as reported for less extreme plasma such as in the development of diamond films.     

On the use of MWCVD diamond as thermoluminescent gamma dosimeter

The thermoluminescence (TL) characterization of microwave plasma assisted chemical vapor deposition diamond (MWCVD) films of 6 and 12 μm thickness grown on (1 0 0) silicon substrates was performed. The films exhibited a single well-resolved TL peak around 580 K at doses lower than 40 Gy. As the irradiation dose increased the TL peak broaden and shifted towards the low temperature side of the glow curve. The diamond samples exposed to 0.67 Gy/min ⁶⁰Co gamma radiation displayed a linear dose behavior up to 100 Gy being non-linear for higher doses. The 12 μm film showed lower TL efficiency as compared to the 6 μm specimen. The discrepancy was attributed to the non-uniform distribution of nucleated sp³ diamond and sp² bonded carbon on the substrate as revealed by SEM micrograph and Raman spectroscopy of the samples. The integrated TL glow curve of the samples exhibited low room temperature thermal fading and 3% reproducibility. The results show that MWCVD diamond films possess promising properties for radiation dosimetry applications.     

Growth of 4" diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters,and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230-380 K.The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra.Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples,respectively.TC,as high as 1950 ± 230 W m-1 K-1 at room temperature,is measured for the most perfect material.A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.     

CORROSION BEHAVIOURS OF ION IRRADIATED Ta AND Co-Cr-W FILMS ON STAINLESS STEEL

Thin films of Ta or Co- Cr- W deposited on 2Crl3 stainless steel were irradiated with 200 keV Xe+ or 190 keV N+ at room temperature. The results of electrochemical corrosion behaviour of the resulting films in H2SO4 solution show that the corrosion resistance is greatly improved compared with that of virgin steel. Energy dispersive X-ray analysis, Rutherford backscattering spectrometry and X-ray photoelectron spectrometry were used to determine the surface composition of the irradiated layers, and Ta depth profile and chemical states.     

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".     

Synthesis of Diamond-Like Carbon Films Using Hot Filament-Aided Microwave Plasma Chemical Vapor Deposition

1. IntroductionDiamond-like carbon (DLC) films have receivedconsiderable attention recently because their inher-ent properties such aJs hardness, thermal conductiv-ity and electrical resistance are excellent and closeto those of a diamond. The DLC films have beenprepared by a variety of methods, for instance, radiofrequency (RF) plasma deposition [l], ion beam de-position [2] and electron cyclotron resonance (ECR)chemical vapor deposition [3]. As sllrface wave dis-charges [4] have advanta…