Investigation of optical emission spectroscopy in diamond chemical vapor deposition by Monte Carlo simulation

The optical emission spectra(atomic hydrogen(Hα,Hβ,Hγ),atomic carbon C(2p3s→2p2:λ=165.7 nm) and radical CH(A2△→X2П:λ=420-440 nm))in the gas phase process of the diamond film growth from a gas mixture of CH4 and H2 by the technology of electron-assisted chemical vapor deposition (EACVD)have been investigated by using Monte Carlo simulation.The results show that the growth rate may be enhanced by the substrate bias due to the increase of atomic hydrogen concentration and the mean temperature of electrons.And a method of determining the mean temperature of electrons in the plasma in-situ iS given.The strong dependence on substrate temperature of the quality of diamond film mainly attributes to the change of gas phase process near the substrate surface.     

Structure of diamond nanoparticles grown by chemical vapor deposition

We studied the structure of diamond nanoparticles grown by chemical vapor deposition. SEM images show that the material contains cubic, hexagonal, and possibly icosahedral structures ranging in size from 10 to 200 nm. Raman spectroscopy shows bands, which are characteristic of crystalline diamond, E_2g mode of hexagonal diamond, a-C, and graphite.     

Synthesis and characterization of silica nanosprings by a low temperature chemical vapor deposition

Silica nanosprings were synthesized using a simple, low temperature, chemical vapor deposition method via a vapor–liquid–solid mechanism. Nanosprings with excellent uniformity and helicity in high and repeatable yields have been observed. The morphology and crystal structure of the nanosprings were characterized by scanning electron microscopy and transmission electron microscopy. The chemical composition of the nanosprings was determined using the energy-filtered transmission electron microscopic method. The as-grown nanomaterials were confirmed to be amorphous silica with irregularly shaped Au catalytic particles located at the tips. In addition, we propose a spontaneous spinning growth model to explain the formation of such helical nanostructures.     

激光轴向偏焦法平整化CVD金刚石膜

利用Nd:YAG型金刚石精密激光切割机,采用激光轴向偏焦法对化学气相沉积（CVD）法制备的金刚石膜表面进行扫描式平整化处理,利用扫描电子显微镜（SEM）、粗糙度仪和金相显微镜对平整化后的金刚石表面进行表征,研究了激光充电电压和焦点位置对扫描凹槽宽度和深度的影响,以及扫描间距对平整化效果的影响。研究结果表明:扫描凹槽宽度随激光充电电压的升高而增大;凹槽深度随激光充电电压的升高而增大,随偏焦量的增大而增大。激光轴向偏焦法对CVD金刚石膜进行平整化处理后,其粗糙度显著减小,利用氢等离子体对其表面进行刻蚀处理,能够有效去除表层石墨,从而达到理想的平整化效果。     

激光轴向偏焦法平整化CVD金刚石膜

利用Nd：YAG型金刚石精密激光切割机,采用激光轴向偏焦法对化学气相沉积（CVD）法制备的金刚石膜表面进行扫描式平整化处理,利用扫描电子显微镜（SEM）、粗糙度仪和金相显微镜对平整化后的金刚石表面进行表征,研究了激光充电电压和焦点位置对扫描凹槽宽度和深度的影响,以及扫描间距对平整化效果的影响。研究结果表明：扫描凹槽宽度随激光充电电压的升高而增大;凹槽深度随激光充电电压的升高而增大,随偏焦量的增大而增大。激光轴向偏焦法对CVD金刚石膜进行平整化处理后,其粗糙度显著减小,利用氢等离子体对其表面进行刻蚀处理,能够有效去除表层石墨,从而达到理想的平整化效果。     

Rapid nucleation of diamond films by pulsed laser chemical vapor deposition

The nucleation of diamond films could be greatly enhanced on mirror-polished Si substrate by a pulsed Nd:YAG laser beam without any thermal- and plasma-assisted processes during a very short time. The nucleation density increased with decreasing laser power density from 1.38×10¹⁰ to 1.17×10⁹ W/cm² and deposition pressure from 1013 to 4 mbar. The pulsed laser beam made no contribution to enhance nucleation at substrate temperature as low as 650°C. X-ray diffraction measurements showed the (1 1 1) diffraction peak of diamond for the samples obtained using only pulsed laser during 40 min. The enhanced nucleation and growth of diamond crystallites were attributed to effective excitation of reactive gases and etching of non-diamond carbon phases by the pulsed laser beam.     

Response of chemical vapor deposition diamond detectors to X-ray

The outstanding properties of diamond, such as radiation hardness, high carrier mobility, high band gap and breakdown field, distinguish it as a good candidate for radiation detectors. The detector's performance is strongly limited by the concentration of defects (grain boundaries and/or impurities) in chemical vapor deposition (CVD) diamond. We report the response of free-standing CVD diamond with a thickness of 300 μm and area of 2×2 cm², synthesized by a hot filament chemical vapor deposition (HFCVD) technique, to 5.9 keV X-ray radiation from a ⁵⁵Fe source. The linear I-V characteristics indicate that CVD diamond has good ohmic contacts. This detector also shows good results such as dark-current of 10⁻⁸ A, photocurrent of 10⁻⁶ A, energy resolution <0.4%, and a high ratio of signal to noise.     

电子助进化学气相沉积金刚石中发射光谱的蒙特卡罗模拟

采用蒙特卡罗方法，对源料气体为CH4/H2混合气的电子助进化学气相沉积（EACVD）中 的氢原子(H)、碳原子(C)以及CH基团的发射过程进行了模拟.研究了CH4浓度、反应室气压 和衬底偏压等工艺参数对发射光谱及成膜的影响.研究发现，CH基团可能是有利于金刚石薄 膜生长的活性基团，而碳原子不是；偏压的升高可提高电子平均温度及衬底表面附近氢原子 的相对浓度；通过氢原子谱线可测定电子平均温度并找到最佳成膜实验条件.该结果对EACVD 生长金刚石薄膜过程中实时监测电子平均温度，有效控制工艺条件，生长出高质量的金刚石 薄膜具有重要的意义. 关键词： 蒙特卡罗模拟 金刚石薄膜 发射光谱     

CVD金刚石膜的结构分析

利用x射线广角衍射和低角掠入射散射谱、正电子湮没谱、定性分析软件和Positronfit程序，研究了生长在Si（100）基底上的金刚石膜微结构.研究发现，在样品邻近基底区域为纳米 多晶结构，具有弱的［111］织构；在邻近表面区域为微米多晶结构，具有强的［220］织构 .金刚石膜样品有空位、空位团和空洞3种缺陷，其中主要缺陷是大约10个空位形成的空位团 . 关键词： 金刚石膜 化学气相沉积 x射线掠入射 正电子湮没谱     

同质与异质外延掺杂CVD金刚石薄膜的结构与性能

采用化学气相沉积(CVD)技术,以高温高压(HTHP)合成的(100)金刚石和p型(100)Si为衬底制备了硫掺杂和硼-硫共掺杂金刚石薄膜,利用原子力显微镜(AFM)、扫描隧道显微镜(STM)及隧道电流谱(CITS)等手段分析同质和异质外延CVD掺杂金刚石薄膜的结构和性能.结果表明:异Si衬底上CVD金刚石的形核密度低,薄膜表面比较粗糙,粗糙度达到18.5nm;同质HTHP金刚石衬底上CVD金刚石薄膜晶粒尺寸约为10—50nm,表面平整,表面粗糙度为1.8nm.拉曼测试和电阻测量的结果显示,在HTHP金刚 关键词： 金刚石 掺杂 外延     

Synthesis of flower-like WS2 by chemical vapor deposition

Flower-like tungsten disulfide (WS₂) with a diameter of 5-10 μm is prepared by chemical vapor deposition (CVD). Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Raman spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy are used to characterize its morphological and optical properties, and its growth mechanism is discussed. The key factors for the formation of flower-like WS₂ are determined. Firstly, the cooling process causes the generation of nucleation dislocations, and then the "leaf" growth of flower-like WS₂ is achieved by increasing the temperature.     

ZnO nanorods grown on ZnSe particles by the chemical vapor deposition method

A novel structure of ZnO nanorods on microsized ZnSe particles has been prepared through a chemical vapor deposition technique using Zn and Se powders as the sources. The dimension of the nanorods can be controlled by adjusting the growth temperature, time and the Zn : Se ratio. Through the investigation of the effects of synthesis time and Zn : Se ratio on the formation of ZnO nanorods on ZnSe microparticles, it is proposed that the synthesis of the ZnO–ZnSe structures involves a two-stage formation. The growth of ZnO nanorods can be described by the vapor–solid mechanism. The photoluminescence of the ZnO–ZnSe structures has also been studied. PACS 73.21.-b; 78.55.Et; 61.10.Nz; 61.46.+w; 68.65.-k     

High pressure studies using two-stage diamond micro-anvils grown by chemical vapor deposition

Ultra-high static pressures have been achieved in the laboratory using a two-stage micro-ball nanodiamond anvils as well as a two-stage micro-paired diamond anvils machined using a focused ion-beam system. The two-stage diamond anvils’ designs implemented thus far suffer from a limitation of one diamond anvil sliding past another anvil at extreme conditions. We describe a new method of fabricating two-stage diamond micro-anvils using a tungsten mask on a standard diamond anvil followed by microwave plasma chemical vapor deposition (CVD) homoepitaxial diamond growth. A prototype two-stage diamond anvil with 300?µm culet and with a CVD diamond second stage of 50?µm in diameter was fabricated. We have carried out preliminary high pressure X-ray diffraction studies on a sample of rare-earth metal lutetium sample with a copper pressure standard to 86?GPa. The micro-anvil grown by CVD remained intact during indentation of gasket as well as on decompression from the highest pressure of 86?GPa.     

Bolometric detector embedded in a polycrystalline diamond grown by chemical vapor deposition

A fast bolometric detector embedded in a plate of chemical-vapor-deposited polycrystalline diamond was developed and fabricated. The working element of the bolometer is a buried graphitized layer (with temperature-sensitive resistance) fabricated in the bulk of a diamond by C⁺ ion implantation followed by annealing. The kinetics of the response of the structure to irradiation with light from an LGI-21 pulsed nitrogen laser (λ = 337 nm, τ_P ～ 8 ns) were studied. The room-temperature response width at half-maximum is ～ 20 ns. Using the space-time distribution of responses of the structure, thermal (bolometric) signals were resolved from signals of different nature (photoconductivity or photovoltage).     

Furnace chemical vapor deposition bismuth-doped silica-core holey fiber

A bismuth-doped-pure-silica holey fiber is fabricated using a fiber preform made by the furnace chemical vapor deposition method. The spectroscopic properties of the fiber are studied, and laser action at λ=1450 nm with an efficiency of 12% is demonstrated.     

Synthesis of micro- or nano-crystalline diamond films on WC-Co substrates with various pretreatments by hot filament chemical vapor deposition

Diamond films deposited on tungsten carbide can lead to major improvements in the life and performance of cutting tools. However, deposition of diamond onto cemented tungsten carbide (WC-Co) is problematic due to the cobalt binder in the WC. This binder provides additional toughness to the tool but results in poor adhesion and low nucleation density of any diamond film. A two-step chemical etching pretreatment (Murakami reagent and Caro acid, (MC)-pretreatment) and a boronization pretreatment have both been used extensively to improve adhesion of CVD diamond film on WC-Co substrates. Here we discuss the applicability of MC-pretreatment for a range of Co-containing WC-Co substrates, and demonstrate a controlled synthesis process based on liquid boronizing pretreatment for obtaining smooth and dense micro- or nano-crystalline diamond films on high Co-containing WC-Co substrates. Substrate treatments and deposition parameters were found to have major influences on the smoothness, structure and quality of the diamond films. The best quality diamond films were achieved under conditions of relatively high substrate temperature (T_s) and the best adhesion was achieved at T_s = 800 °C.     

N-methylpyrrolidine-based precursors for chemical vapor deposition of GaNx particles

An attempt to prepare a metalorganic precursor of gallium with reactivity at low temperature in chemical vapor deposition (CVD) systems was done by reacting N-methylpyrrolidine with metal gallium or gallium nitrate under mild conditions. The precursors were bubbled into a CVD assemblage and then reacted with ammonia at temperatures between 400 and 700 °C. The depositions onto silicon substrates were pyramidal particles of 100 nm width at the base and up to 55 nm in height. The rise in growth temperature increased particle density from 0.9 to 27.1 particles per square micron, but reduced the height from 50 to 10 or 2 nm. XPS spectra showed the presence of gallium and nitrogen. The intensity of the gallium spectrum decreased as the process temperature increased indicating that GaN_x particles were deposited rather than the stoichiometric gallium nitride (GaN). An additional N1s band of impurities appeared whose intensity increases with the reaction temperature. The lower impurity content corresponded to the sample prepared with Ga(NO₃)₃ at 400 °C.     

Synthesis of carbon nanotubes by ECR plasma-assisted chemical vapor deposition

Carbon nanotubes have been grown using an electron cyclotron resonance (ECR) plasma source at a substrate temperature of 500 °C. Methane has been used as the source gas. A network of carbon nanotubes has been observed in scanning electron microscopy. Transmission electron microscopy revealed that the structure consists of straight, Y-junction and ring-like nanotubes. Further, electron diffraction of the nanotubes confirms a graphite crystal structure. PACS 81.16.He; 68.37.Lp; 68.37.Hk; 85.35.Kt; 75.75.+a     

Chemical vapor deposition of diamond

In the recent decade a multitude of diamond thin film production methods has been developed, generally based on chemical vapor deposition processes from thermally or plasma activated gas phases. Diagnostic studies, growth experiments and numerical kinetic investigations have in recent years lead to an improved understanding of the prerequisites of continuous diamond growth and of the chemical processes involved. While the mechanism of carbon incorporation into the diamond surface is not yet known completely, the gas-phase species which are essential in a diamond-growth atmosphere can be narrowed to a small number, whose role in the gas-phase chemistry is quite well known.