电子束诱导的ITO薄膜多晶化研究

在对ｒｆ一溅射制得的掺ＳｎＯ２和Ｉｎ２Ｏ３薄膜（ＩＴＯ）的电性能进行测量时，发现样品的方块电阻（Ｒ□）经热处理后明显下降．为此我们用ＴＥＭ对薄膜的显微结构进行了动态观察，在观察的过程中随电子束的轰击发现有多晶化转变，即在电子束轰击后薄膜由主要以非晶态构成的结构变成了主要为平均晶粒尺寸约５０ｎｍ的多晶态结构．本文对这一薄膜显微结构的变化与其电性能之间的关系进行了详细地讨论．

a-SiGe_x∶H薄膜准分子激光晶化的研究

用KrF准分子激光、XeCl准分子激光在不同条件下对Ge含量不同的四种a－SiGex∶H样品进行退火。只要激光退火能量密度合适，Ge含量不同的a－siGex∶H薄膜都可以被多晶化；随着Ge含量的增加，激光晶化阈值能量密度降低，耐退火能力也降低；在相同的激光晶化能量密度下，Ge含量越高的薄膜，激光晶化的效果越好，晶粒尺寸长得越大。

Fe基非晶合金涂层的多晶型晶化过程研究

等离子喷涂Fe基非晶合金涂层的晶化温度在 5 90℃左右。在高于晶化温度热处理时 ,涂层首先以多晶型晶化方式直接结晶形成亚稳的Fe2 3(c ,B) 6 和Fe2 3B6 化合物相。随热处理时间延长 ,Fe2 3(C ,B) 6 和Fe2 3B6相发生分解 ,逐渐转变为更稳定的Fe3B相和Fe固溶体相。热处理温度越高 ,Fe2 3(C ,B) 6 相和Fe2 3B6 相的分解转变速度越快。随热处理温度升高或时间的延长 ,晶化涂层的硬度呈线性降低。经 5 90℃ ,4h热处理后 ,涂层结晶形成纳米晶组织 ;经 6 6 0℃ ,4h热处理后 ,涂层结晶形成树枝状晶组织 ,随热处理温度升高 ,涂层中扁平状粒子间结合增强并趋于熔合 ,晶粒发生长大。

水平定向凝固法合成砷化镓多晶

采用水平定向凝固法合成砷化镓多晶,定向凝固炉分为3个温区,砷单质在低温区(约630℃)升华,通过中温区后在高温区(1 250~1 255℃)与镓逐渐化合为砷化镓多晶.石英变形、砷端杂质、多晶表面氧化以及多晶尾端富镓是合成砷化镓多晶过程中易出现的宏观缺陷.通过对原料配方设计、砷蒸气压控制以及炉子降温程序设计等进行优化,成功获得了完整性好且电学性能指标优异的砷化镓多晶.多晶的迁移率在4 800~5 400cm2/(V·s),载流子浓度为1015~1016 cm-3量级,完全满足砷化镓单晶制备要求.

多晶矿化黑陶瓷红外涂料及其在炉窑上的应用

红外加热用多晶矿化黑陶瓷红外辐射涂料耐火温度达1790℃以上,法向全发射率ε_n大于0.90。它能涂抹于炉窑内衬耐火砖表面,起抗高温气流冲刷、侵蚀,提高炉窑使用寿命和节能等多种效果。已大量成功地应用于各种加热炉、均热炉、退火炉和锅炉等。

新型砷化镓多晶高压合成炉设计与制造

在分析原卧式砷化镓多晶合成炉缺陷的基础上,借鉴其它进口砷化镓单晶炉体部分结构优点,综合创新设计等制造出立式砷化镓多晶合成炉。经过300多炉次砷化镓多晶合成,证实新型砷化镓合成炉具有装、取料方便、电极不易沉积砷、炉体清洁快速等优点。由于提高了新合成炉密闭性及增强了石墨系统稳定性,从而保证了砷化镓多晶合成产品的一致性。

砷化镓多晶表面清洗技术的研究

根据实际生产经验,分析了GaAs多晶料表面杂质的类型、产生原因及对后续单晶生长的影响,明确了多晶表面清洗工艺的重要性,介绍了针对不同类型杂质的清洗方法和原理,并在此基础上进行了多晶表面清洗实验,结果表明:无论是酸性清洗液还是碱性清洗液,都能达到去除GaAs多晶表面杂质的目的;Ga和As各自的氧化物在酸、碱溶液中溶解的难易程度决定了利用不同清洗液清洗后,多晶表面的光亮程度;从安全性和环保性角度来看,碱性清洗液是清洗多晶料表面更好的选择。

无液封GaAs多晶合成技术

利用As、Ga、GaAs的性质,开发出一种新的GaAs多晶合成方法。开展了Φ130 mm合成系统的温度、压力优化实验。采用石墨盖代替BN坩埚盖,开发了100 mm新合成石墨系统,通过工艺实验确定加热电流、温度、压力随时间的变化,稳定了Φ100 mm无液封GaAs多晶合成工艺。通过大量的实验,逐渐确定了两套无液封GaAs多晶合成的温度压力曲线,固化了坩埚密封结构,掌握了调节GaAs多晶料中化学计量比的方法。

ZnSe多晶料预处理原理与方法

以ZnSe多晶料的预处理为例,阐述了Ⅱ-Ⅵ族高熔点化合物的预处理方法与原理。生长单晶体,不仅仅要求原料有足够高的纯度,更为重要的是需要通过原料的预处理,获得具有合适化学比的高纯多晶原料。结合ZnSe材料的升华特性和杂质分布,对区域升华法处理工艺参数进行了分析,确定了源区温度应略低于1100℃,而沉积温度应高于900℃。选择较窄的升华-沉积温度范围更有利于杂质的去除。沉积区的温度越接近单晶生长温度,就越容易获得化学比较为合适的原料多晶。

Recent advances in immobilized enzymes on nanocarriers

Recent progress in nanotechnology has provided high-performance nanomaterials for enzyme immobilization.Nanobiocatalysts combining enzymes and nanocarriers are drawing increasing attention because of their high catalytic performance,enhanced stabilities,improved enzyme-substrate affinities,and reusabilities.Many studies have been performed to investigate the efficient use of cellulose nanocrystals,polydopamine-based nanomaterials,and synthetic polymer nanogels for enzyme immobilization.Various nanobiocatalysts are highlighted in this review,with the emphasis on the design,preparation,properties,and potential applications of nanoscale enzyme carriers and nanobiocatalysts.

Design and construction of a film of mesoporous single-crystal rutile TiO_2 rod arrays for photoelectrochemical water oxidation

A film of mesoporous single-crystal rutile TiO2 rod arrays supported on a transparent conductive glass substrate was synthesized with the assistance of a template layer of closely packed silica nanospheres. This film was used as a photoanode and showed significant improvement for photoelectrochemical water oxidation compared with a reference film of nonporous single-crystal rutile TiO2rod arrays.

Pulsed Laser Deposition ZnS Buffer Layers for CIGS Solar Cells

Polycrystalline ZnS films were prepared by pulsed laser deposition （PLD） on quartz glass substrates under different growth conditions at different substrate temperatures of 20, 200, 400, and 600 ℃, which is a suitable alternative to chemical bath deposited （CBD） CdS as a buffer layer in Cu（In,Ga）Se2 （CIGS） solar cells. X-ray diffraction studies indicate the films are polycrystalline with zinc-blende structure and they exhibit preferential orientation along the cubic phase β-ZnS （111） direction, which conflicts with the conclusion of wurtzite structure by Murali that the ZnS films deposited by pulse plating technique was polycrystalline with wurtzite structure. The Raman spectra of grown films show Al mode at approximately 350 cm^-1, generally observed in the cubic phase β-ZnS compounds. The planar and the cross-sectional morphology were observed by scanning electron microscopic. The dense, smooth, uniform grains are formed on the quartz glass substrates through PLD technique. The grain size of ZnS deposited by PLD is much smaller than that of CdS by conventional CBD method, which is analyzed as the main reason of detrimental cell performance. The composition of the ZnS films was also measured by X-ray fluorescence. The typical ZnS films obtained in this work are near stoichiometric and only a small amount of S-rich. The energy band gaps at different temperatures were obtained by absorption spectroscopy measurement, which increases from 3.2 eV to 3.7 eV with the increasing of the deposition temperature. ZnS has a wider energy band gap than CdS （2.4 eV）, which can enhance the blue response of the photovoltaic cells. These results show the high-quality of these substitute buffer layer materials are prepared through an all-dry technology, which can be used in the manufacture of CIGS thin film solar cells.

Technical Challenges and Progress in Fluidized Bed Chemical Vapor Deposition of Polysilicon

Various methods for production of polysilicon have been proposed for lowering the production cost andenergy consumption, and enhancing productivity, which are critical for industrial applications. The fluidized bed chemical vapor deposition （FBCVD） method is a most promising alternative to conventional ones, but the homogeneous reaction of silane in FBCVD results in unwanted formation of fines, which will affect the product qualityand output. There are some other problems, such as heating degeneration due to undesired polysilicon deposition on the walls of the reactor and the heater. This article mainly reviews the technological development on FBCVD of polycrystalline silicon and the research status for solving the above problems. It also identifies a number of challenges to tackle and principles should be followed in the design ofa FBCVD reactor.

Influence of multi-pass friction stir processing on microstructure and mechanical properties of 7B04-O Al alloy

Three-pass friction stir processing(FSP)with different moving distances of the stirring tool between the two successivepasses,50%diameter of the pin(traditional way)and50%diameter of the shoulder(novel way),was conducted on7B04-O Al alloy.The result shows that an improvement in the mechanical properties of the processed zone is accomplished due to grain and secondphase particles refinement.The hardness of the multi-pass FSP(M-FSP)sample is about HV40higher than that of the base metal.And the tensile strength of the M-FSP specimens is also significantly increased to about1.4times that of the base metal.Besides,theweak region of the processed zone is mainly dependent on the moving distance,where it is the previous pass stir zone in thetraditional way and the transitional zone in the novel way.Increasing the rotational speed narrows the weak region in the novel way,while it does not in the traditional way.

CdS Thin Films Deposited by CBD Method on Glass

CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro- scope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X- ray diffraction results showed the film structure was a mixture of two phases： hexagonal and cubic, and it was very important to controll deposition time to the film＇s crystal phase. All films in depth of approxilnate 100 nm existed above 65% transmittance, the absorption edge became ＂red-shift＂ with temperature rising. At 60 and 70℃, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90℃ the energy band gap was less than 2.42 eV and increased little when the time changed from 10min to 15 nfin at 80℃.

Alumina Photonic Crystals with Defect Modes for Sensor Application

One-dimensional alumina photonic crystals with defect modes were successfully fabricated through inserting a constant voltage waveform into the periodic voltage signals. The trans-mission spectra show that the thickness of defects plays a key role in determining the trans-mittance of defect modes. When the thickness was ？180 nm, an obvious defect mode with the high transmittance of 55% and a narrow full width at half maximum of 18 nm was observed in the original photonic band gaps. The defect mode shifted linearly with the increasing of refractive index of the analytes infiltrated into pores, indicating its potential application in chemical sensing or bio-sensing.

Multi sites vs single site for catalytic combustion of methane over Co3O4(110):A first-principles kinetic Monte Carlo study

Single-atom catalysts have been applied in many processes recently.The difference of their kinetic behavior compared to the traditional heterogeneous catalysts has not been extensively discussed yet.Herein a complete catalytic cycle of CH4 combustion assuming to be confined at isolated single sites of the Co3O4(110)surface is computationally compared with that on multi sites.The macroscopic kinetic behaviors of CH4 combustion on Co3O4(110)is systematically and quantitatively compared between those on the single site and multi sites utilizing kinetic Monte Carlo simulations upon the energetic information from the PBE+U calculation and statistic mechanics.The key factors governing the kinetics of CH4 combustion are disclosed for both the catalytic cycles respectively following the single-site and multi-site mechanisms.It is found that cooperation of multi active sites can promote the activity of complete CH4 combustions substantially in comparison to separated single-site catalyst whereas the confinement of active sites could regulate the selectivity of CH4 oxidation.The quantitative understanding of catalytic mechanism paves the way to improve the activity and selectivity for CH4 oxidation.

Preparation and electro-catalytic activity of nanoporous palladium by dealloying rapidly-quenched Al_(70)Pd_(17)Fe_(13) quasicrystalline alloy

The formation of nanoporous Pd was studied by electro-chemical dealloying a rapidly-quenched Al70Pd17Fe13 quasicrystal alloy in dilute NaCl aqueous solution,and the electro-catalytic activity of the nanoporous Pd towards methanol electro-oxidation was evaluated by cyclic voltammetry in 1 mol/L KOH solution.XRD and TEM analyses revealed that nano-decomposition of quasicrystal grains occurred in the initial stage of dealloying,and the fully dealloyed sample was composed of FCC-Pd phase.Scanning electron microscopy observation indicated that a maze-like nanoporous pattern was formed in the dealloyed sample,consisting of percolated pores of 5.20 nm in diameter in a skeleton of randomly-orientated Pd nano-ligaments with a uniform thickness of^5 nm.A retention of^12 at.%Al in the Pd nano-ligments was determined by energy dispersive X-ray spectroscopy(EDS).The nanoporous Pd demonstrated obvious electro-catalytic activity towards methanol electro-oxidation in alkaline environment.

Reduction and subsequent carburization of pre-oxidation magnetite pellets

Magnetite is a kind of iron ore that is difficult to carburize.In order to improve the carburizing performance of magnetite pellet,pre-oxidation treatment was carried out,and the oxidation,reduction and carburization behaviors of magnetite pellet were investigated in this study.The magnetite pellet was oxidized in the air and carburized in CO-CO_(2)-H_(2) gas mixtures,the oxidation,reduction and carburization behaviors were demonstrated by detecting phase change,microstructure,carburizing index via thermogravimetry,X-ray diffraction(XRD),infrared carbon-sulfur analyzer,and scanning electron microscope(SEM).The results show that the dense magnetite particles inside pellet are oxidized to porous hematite particles,and the Fe_(3)O_(4) transforms to Fe_(2)O_(3) with high lattice defect concentration during the pre-oxidation process.Then the porous hematite particles and newly formed Fe_(2)O_(3) significantly promote the reduction efficiency.Porous metallic iron particles are produced in the reduction process.Finally,both high reduction efficiency and the porous structure of metallic iron particles dramatically enhance the carburization efficiency of pellet.High preoxidation temperature favors to the carburization of magnetite pellet.However,the carburized index decreases due to the recrystallization of iron oxide when the temperature extends to 1000℃.The optimum pre-oxidation temperature for magnetite pellet carburization is 900℃.

Numerical simulation of chemical vapor deposition reaction in polysilicon reduction furnace

Three-dimensional model of chemical vapor deposition reaction in polysilicon reduction furnace was established by considering mass, momentum and energy transfer simultaneously. Then, CFD software was used to simulate the flow, heat transfer and chemical reaction process in reduction furnace and to analyze the change law of deposition characteristic along with the H_2 mole fraction, silicon rod height and silicon rod diameter. The results show that with the increase of H_2 mole fraction, silicon growth rate increases firstly and then decreases. On the contrary, SiHCl_3 conversion rate and unit energy consumption decrease firstly and then increase. Silicon production rate increases constantly. The optimal H_2 mole fraction is 0.8-0.85. With the growth of silicon rod height, Si HCl3 conversion rate, silicon production rate and silicon growth rate increase, while unit energy consumption decreases. In terms of chemical reaction, the higher the silicon rod is, the better the performance is. In the view of the top-heavy situation, the actual silicon rod height is limited to be below 3 m. With the increase of silicon rod diameter, silicon growth rate decreases firstly and then increases. Besides, SiHCl_3 conversion rate and silicon production rate increase, while unit energy consumption first decreases sharply, then becomes steady. In practice, the bigger silicon rod diameter is more suitable. The optimal silicon rod diameter must be over 120 mm.