喷淋式GaN-MOCVD反应室的CFD数值仿真及优化

利用计算流体力学(CFD)方法对某型立式喷淋式金属有机物化学气相沉积(MOCVD)反应室流场进行了三维数值仿真,研究了影响MOCVD反应室流场结构的各工作参数(流量、温度、压力)的作用机制,并对试制中的MOCVD设备的几何结构及进气方式进行了改进,采用了圆弧形过渡拐角及泊肃叶型入口速度剖面,以形成稳定均匀的流场,从而保证氮化镓(GaN)的生长质量。     

三层热壁金属有机化学气相外延流场计算机模拟

本文对三层热壁水平流金属有机化学气相沉积(MOCVD)真空反应腔的设计以及最终流场分布都进行了理论模拟。在选择优化喷管排布基础上,在衬底托盘、衬底四周底壁,以及衬底所在区域上壁临近区域范围加热,形成局部热壁外延真空反应腔体。此外,对于真空腔体设计,顶层与底层流动速度,都进行细致研究,确保在材料生长区域的壁面,反应前驱物源气体保持在稳定且无漩涡流动状态,并使反应物主要分布在衬底位置处,有效提高反应物利用率,并避免在腔壁等处发生反应,最后进行热壁MOCVD材料生长,得到厚度分布比较均匀,x射线双晶衍射的半峰全宽(FWHM)为149.8弧度秒,表明生长出质量良好的氮化镓(GaN)薄膜单晶材料。     

一维GaN纳米材料制备及其光电器件研究进展

一维GaN纳米材料相对于薄膜材料在光电器件应用方面具有诸多优势,本文主要论述一维GaN纳米材料的主要制备方法及其光电器件应用的研究进展。首先分别介绍采用MOCVD、MBE、CVD及模板法制备一维GaN纳米材料,重点论述GaN纳米材料的结构与形貌调控。其次介绍一维GaN纳米材料分别应用于主要光电器件包括LED、太阳能电池、激光器及光探测器的研究动态,讨论纳米材料性能、结构以及制备技术对其器件性能的影响。最后对一维GaN纳米材料的发展与应用前景进行展望。     

阳极氧化铝作缓冲层的Si基GaN生长

尝试了Si基上生长GaN外延层的一种新的缓冲层材料一阳极氧化铝，在Si（111）衬底上电子束蒸发铝膜，经阳极氧化后放入MOCVD系统中退火，然后进行GaN外延生长，对材料的微结构和电学性质进行了测量和分析，并将得到的GaN材料制备成光导型的紫外光电探测器，器件在330－380nm紫外光区域有明显的响应，最后响应度为3．5A／W（5V偏压）。     

国内部分

91232 金属有机化合物汽相淀积(MOCVD)化合物半导体的现状和发展有色金属,1988,12(4),292～297 介绍了MOCVD化合物半导体的装置、材料及其器件应用的现状与发展,并对此方法的基础研究进展、安全等问题进行了讨论。     

碳基材料烧蚀下的热化学非平衡流场数值模拟研究

针对飞行器再入过程中碳基材料的烧蚀现象,采用考虑十三组元三十四反应式的流场化学反应模型,结合防热材料的烧蚀反应模型和结构热传导模型,建立了热化学非平衡烧蚀流场/结构温度场双向耦合数值模拟方法,并开展了算例验证。通过对三维球头模型烧蚀效应的模拟,获得了结构内部的温度场分布和烧蚀流场参数。结果表明,烧蚀效应改变了流场中化学反应组分的分布特性,同时增大了激波脱体距离,在工程设计中需要加以考虑。     

MOCVD方法在TiO2纳米粉末制备中的应用

众所周知,MOCVD方法是制备薄膜材料的重要方法之一,现已广泛应用于半导体薄膜、铁电薄膜和超导薄膜等的制备.在以前的工作中,我们设计、加工、安装、调试、建立了一套可计算机自动控制的热壁低压MOCVD设备,制备出了TiO2纳米粉末,得到了一些初步结果.本文详细研究了热壁低压MOCVD方法在TiO2纳米粉末制备中的应用,通过合理设计反应室和收集区域,在采用反应区域和收集区域之间无任何过渡区域的收集方式,制备出了TiO2纳米粉末.采用X射线衍射技术研究了沉积温度对TiO2纳米粉末的晶体结构和平均晶粒尺寸的影响规律.在500℃～1000℃范围内,粉末均为锐钛矿结构,平均晶粒尺寸7.4～15.2nm,700℃条件下制备的TiO2纳米粉末的平均晶粒尺寸最小.透射电子显微镜观察表明,在最佳沉积温度700℃条件下制备的TiO2粉末粒度均匀性好,粒径约为5～8nm.     

大规模集成电路制造工艺对特种气体的要求

叙述了大规模集成电路的发展,包括线宽、管芯面积与制造工艺对特种气体中尘埃数和粒径的要求、颗粒与成品率的关系,以及在不同级别洁净室中生产器件对成品率的影响。详细介绍了工艺气体中杂质对器件性能的影响。还介绍了大规模集成电路材料及器件和化合物半导体材料及器件生产工艺中使用的各种气体。对国外用于MOCVD、LSI及亚微米集成电路制造用气体的污染控制也作了介绍。     

纳米反应多层膜的制备及应用

纳米反应多层膜是指两种或两种以上不同材料按一定厚度在衬底上交替沉积形成的薄膜材料。纳米反应多层膜是一种新结构形式的纳米含能材料,可在较低的能量刺激下发生放热反应,产生的热量足以使反应区以特定的速度自持传播,具有反应瞬间完成、放热量大等特点。由于结构可自行设计以及不同于单层膜的特殊性能,纳米反应多层膜可广泛应用于微电子器件、微机械系统(MEMS)等领域。对近年来国内外纳米反应多层膜的制备方法、反应机理以及在器件应用等方面的研究进行了综述,主要分析讨论了机械加工、蒸发镀膜和磁控溅射3种制备方法的优缺点,并对今后纳米反应多层膜的研究方向及研究重点进行了展望。     

立体微型器件的微制造技术及其在微机电系统(MEMS)的应用

综述了近年来与微型机电系统（MEMS）相关的材料微制造和微加工技术的最新研究进展.重点介绍了如何利用硅晶片作为微型模具来制备压电陶瓷和热电材料的微型柱状阵列结构和反应烧结碳化硅微型转子等微制造技术,并展望了材料微制造技术在研制微型医疗器件和微型移动能源方面的应用前景.     

Important aspects for the mass production of GaN-based quantum devices grown by MOCVD

The requirements for mass production of electronic and optoelectronic devices call for the expansion of MOCVD reactor capacity by increasing the number of wafers and the wafer size. Today, MOCVD reactors with capacities of 24 × 2 in. and 8 × 4 in. are readily available. Growth experiments on 4-in. wafers, however, require careful process and reactor hardware design since the effects related to strain and the resultant wafer bow are more pronounced in larger wafers. We have investigated the design criteria for MOCVD hardware and developed a tool for the straightforward optimization of the hardware to a given device structure and process. Morphological and electrical studies show that samples with off-cuts of 0.3° and 0.4° from the c-plane offer the broadest temperature process window for the growth of GaN.     

The influence of reactor height adjustment on properties in GaN films grown on 6H-SiC by metal organic chemical vapor deposition

The influence of reactor height adjustment on properties in GaN films grown on 6H-SiC by metal organic chemical vapor deposition (MOCVD) was investigated. The property of GaN epilayer was investigated by atomic force microscopy, X-ray diffraction, low-temperature (10 K) photoluminescence and the Raman scattering. It is found that, as the spacing between showerhead and susceptor decreased, the growth rate increased and the tensile stress decreased. This result may be useful to control the stress in GaN thin films grown on silicon carbide substrate by MOCVD.     

Growth of CuInSe2 by metallorganic chemical vapour deposition (MOCVD): new copper precursor

Metallorganic chemical vapour deposition (MOCVD) of Cu-In-Se ternary compounds is performed in a horizontal reactor at atmospheric pressure. A copper precursor has been specially developed for this purpose and is used around room temperature. It is hexafluoroacetylacetonato copper mixed with trimethylamine (Cu(hfa)₂, NMe₃). The other source materials are triethylindium (TEIn), trimethylindium (TMIn) and hydrogen selenide (H₂Se). Experimental parameters are detailed and related to the film composition. Properties of thin films are also investigated in the whole range of compositions obtained.     

Metal organic chemical vapor deposition (MOCVD) of oxides and ferroelectric materials

The electrical properties of thin-film oxides span a tremendous range from insulating to superconducting. As a consequence, they are now finding an increasing number of applications in electronics and opto-electronics, both as stand-alone layers and for the provision of added functionality to electronic circuits, especially silicon. The modified precursor delivery technologies (e.g. aerosol or liquid delivery or injection techniques) coupled with improved precursors, and better engineering of the deposition kit, have transformed the prospects for the deposition of these materials by MOCVD. It is now possible to exploit the many traditional advantages of MOCVD, especially over other routes to thin-film oxide deposition. A wide range of oxides and particularly complex ferroelectric oxides are being produced on substrates of up to 200 mm in diameter. This paper highlights the progress and real advantages that MOCVD has for thin-film oxide deposition, including the design of improved precursors. Examples of the deposition of dielectric layers and lead-based ferroelectric layers for uncooled thermal imaging, and MEMS actuation applications are presented.     

Chemical vapor deposition of Ni-C films from bis-(ethylcyclopentadienyl) nickel

Metal-organic chemical vapor deposition (MOCVD) is widely used for deposition of various nickel-containing coatings, such as catalytic nickel thin films and nanoparticles, nickel silicide alloys and magnetic carbon-nickel nanocomposite layers. Here we report preliminary results from an attempt to use bis-(ethylcyclopentadienyl) nickel [(EtCp)2Ni] as a precursor for MOCVD of Ni-C thin films in the (EtCp)2Ni-Ar and (EtCp)2Ni-H2-Ar reaction systems. Mechanism of precursor fragmentation was proposed on the basis of the results from a study of gaseous reaction products in the exhaust line of the reactor by means of mass-spectrometry. It was found that an introduction of hydrogen in the gas phase led to an increase in conversion rate of the precursor. Deposited films were analyzed by means of atomic force microscope (AFM), scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XFS). The effect of hydrogen on growth rate, composition, and morphology of the deposited Ni-C films were experimentally studied.     

用于制备YBCO薄膜的光辅助MOCVD反应器内流动现象的数值研究

对一种制备YBCO薄膜的光辅助MOCVD反应器内的流动现象进行了三维数值模拟研究.在模拟计算中,分别改变基座与进口的相对角度(Φ)、反应器顶壁倾斜角度(Ψ),得出反应器中流场的相应变化.根据对模拟结果的分析,发现当基座平面与进气口轴线之间的夹角Φ=22.5°及反应器顶壁倾角ψ=30°时,基片表面气流速度大小合适,分布均...     

The biocompatibility of titanium in a buffer solution: compared effects of a thin film of TiO<Subscript>2</Subscript> deposited by MOCVD and of collagen deposited from a gel

This study aims at evaluating the biocompatibility of titanium surfaces modified according two different ways: (i) deposition of a bio-inert, thin film of rutile TiO₂ by chemical vapour deposition (MOCVD), and (ii) biochemical treatment with collagen gel, in order to obtain a bio-interactive coating. Behind the comparison is the idea that either the bio-inert or the bio-active coating has specific advantages when applied to implant treatment, such as the low price of the collagen treatment for instance. The stability in buffer solution was evaluated by open circuit potential (OCP) for medium time and cyclic voltametry. The OCP stabilized after 5·10⁴ min for all the specimens except the collagen treated sample which presented a stable OCP from the first minutes. MOCVD treated samples stabilized to more electropositive values. Numeric results were statistically analysed to obtain the regression equations for long time predictable evolution. The corrosion parameters determined from cyclic curves revealed that the MOCVD treatment is an efficient way to improve corrosion resistance. Human dermal fibroblasts were selected for cell culture tests, taking into account that these cells are present in all bio-interfaces, being the main cellular type of connective tissue. The cells grew on either type of surface without phenotype modification. From the reduction of yellow, water-soluble 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT cytotoxicity test), MOCVD treated samples offer better viability than mechanically polished Ti and collagen treated samples as well. Cell spreading, as evaluated from microscope images processed by the program Sigma Scan, showed also enhancement upon surface modification. Depending on the experimental conditions, MOCVD deposited TiO₂ exhibits different nanostructures that may influence biological behaviour. The results demonstrate the capacity of integration in simulated physiologic liquids for an implant pretreated by either method.     

Effects of oxygen on the properties of titania nanoparticles prepared by MOCVD

Anatase titania nanoparticles are prepared using pyrolysis of titanium tetrabutoxide in oxygen free and oxygen containing atmospheres by MOCVD method. Influence of oxygen on the properties of the titania nanoparticles is investigated, followed by discussion. The results show that oxygen influences not only the particle size but also the particle size distribution of the nanoparticles. With increasing oxygen flow rates, the average grain sizes of the nanoparticles decrease and the particle size distributions become uniform. Oxygen exerts great influence on the nucleation rate of the nanoparticles and reaction kinetics occurred in the reactor. The formation of titania nanaoparticles by MOCVD is not a growth controlled process, but is a nucleation rate controlled process.     

LOCA条件下包壳材料感应和电阻加热温升行为的对比研究

目的使有限元模拟技术成为一种切实有效的研究方法,进而为高性能反应堆包壳材料的设计以及可能发生的LOCA(Loss of Coolant Accident)事故下的应急措施等提供理论依据。方法基于COMSOL软件模拟分析典型锆合金核材料在LOCA条件下分别经感应加热和电阻加热后的温升行为。结果感应加热条件下,锆材的体积内最高温度、体积平均温度与表面中心点温度的差值随着温度上升逐渐增大,在1200℃瞬时温度下,温度差值最高,约为41℃。电阻加热条件下,锆材的体积内最高温度、体积内中心温度与表面中心点温度在加热的整个阶段近乎重合,最大差值约为3℃;锆材的体积平均温度、表面平均温度与表面中心点温度的差值出现负值,最大差值约为30℃。结论电阻加热和感应加热虽均适用于堆外研究反应堆失水事故下包壳材料所面临的超高温度及超快升温速率的工况模拟,但限于实际工况下电阻加热速率的滞后性,推荐使用感应加热进行后续的模拟研究工作。相关结果可为高性能反应堆包壳材料的设计提供必要的理论依据。