氧气流量对MPCVD制备微/纳米双层金刚石膜的影响

应用微波等离子体化学气相沉积(MPCVD)技术,以CH4/H2/Ar为主要气源,成功制备出了微/纳米双层金刚石膜.同时,在纳米膜层生长过程中,通过添加O2辅助气体,研究了不同O2流量对微/纳米金刚石膜生长的影响.结果表明,当O2流量在0 ～ 0.8 sccm范围时,所获得的金刚石膜仍为微/纳米两层膜结构;当氧气流量增加到1.2 sccm时,金刚石膜只有一层微米膜结构;而O2流量在0～ 1.2 sccm范围时,纳米层晶粒尺寸及品质与氧气流量成正比例关系.表明适量引入O2可以促进纳米层晶粒长大和提高膜品质.另外,当O2流量为0.8 sccm,所制备的微/纳米金刚石膜不仅品质好,而且生长率也较高.     

椭球谐振腔式MPCVD装置高功率下大面积金刚石膜的沉积

使用自行研制的椭球谐振腔式MPCVD装置,以H2-CH4为气源,在输入功率为9 kW,沉积压力为1.7 ×104 Pa和不同的气体流量条件下制备了金刚石膜.利用扫描电镜、激光拉曼谱对金刚石膜的表面和断口形貌、金刚石膜的品质等进行了表征.实验结果表明,利用椭球谐振腔式MPCVD装置能够在较高的功率下进行大面积金刚石膜的沉积;在高功率条件下,较高质量的金刚石膜的沉积速率可以达到4 ～5 μm·h-1的水平,而气体的流量则会显著影响金刚石膜的品质及其沉积速率.     

工艺参数对高功率MPCVD金刚石膜择优取向的影响研究

使用自行研制的椭球谐振腔式MPCVD装置,以H2-CH4为气源、沉积功率8 kW条件下,在不同CH4浓度、沉积温度和气体流量工艺条件下制备了大面积金刚石膜.使用X射线衍射仪对金刚石膜的择优取向的变化规律进行了研究.实验结果表明,高功率条件下工艺参数对金刚石膜的择优取向有不同程度的影响.在CH4浓度由0.5;上升到1.0;时,金刚石膜的择优取向由(220)转变为(111),由1.O;上升到2.5;时,则由(111)转变为(220)以及(311);在700 ～ 1050℃温度范围内,随着沉积温度的升高,金刚石膜(111)择优取向生长的倾向增高,当沉积温度高于1050℃时,金刚石膜改变了原先的以(111)择优取向生长的趋势,变为了以(100)择优取向生长;在气体流速为200～1000 sccm范围内时,随气体流量的增加,金刚石膜(111)择优取向的倾向增加.当气体流量大于1000sccm时,金刚石膜(111)择优取向的倾向又稍有降低.     

硬质合金球上纳米金刚石膜的形貌与力学性能

采用微波等离子体化学气相沉积法在直径1～5mm硬质合金球体上沉积了5～20 μm厚的纳米金刚石膜.通过扫描电子显微镜、原子力显微镜和拉曼光谱对样品的表面形貌、膜厚均匀性和成份进行了表征.沉积膜表面呈现纳米金刚石典型“菜花”结构,晶粒度为10～20 nm,膜厚均匀,表面粗糙度随沉积膜厚度增加而增大.采用纳米压痕仪测试沉积膜硬度和弹性模量,沉积膜硬度接近40 GPa,弹性模量约为500 GPa.     

气体进出方式对MPCVD大面积金刚石膜均匀性的影响

使用自行研制的MPCVD装置,在功率为8 kW条件下、气体由四种方式进出反应腔体时,在直径65 mm的Si基片上制备了金刚石膜.分别利用数字千分尺和Raman光谱对金刚石膜的厚度和品质均匀性进行了表征.使用Comsol软件模拟了不同进出气方式下腔体内部气体流场的分布,并分析了气体进出方式与所制备金刚石膜均匀性之间的关系.研究表明,反应气体进出位置的改变对等离子体的状态没有明显的影响,但对膜的厚度和品质均匀性有影响较大.气体由中间腔体侧壁上的进气孔进入时,容易造成膜厚度和品质的不均匀性.气体由耦合天线的圆盘中心的进气孔进入时,膜厚度和品质的均匀性明显提高,而由锥形反射体底平面上的出气孔排出时均匀性最优.反应气体流场分布的不均匀性和等离子体区域流速的差异是导致金刚石膜厚度和品质不均匀性的主要原因.     

加氮对直流电弧等离子体喷射金刚石膜生长、形貌和质量的影响

利用直流等离子体喷射化学气相沉积法制备掺氮的金刚石厚膜.本文研究了在甲烷/氩气/氢气中加入氮气对金刚石膜生长、形貌和质量的影响.反应气体的比例由质量流量计控制,在固定氢气(5000sccm)、氩气(3000sccm)、甲烷(100sccm)流量的情况下改变氮气的流量,即反应气体中氮原子和碳原子的变化比例(N/ C比)范围是从0.06到0.68.同时金刚石膜在固定的腔体压力(4kPa)和衬底温度(800℃)下生长.金刚石膜用扫描电镜(SEM)、拉曼谱和X射线衍射表征.结果表明,氮气在反应气体中的大量加入对直流等离子体喷射制备金刚石膜的形貌、生长速率、晶体取向、成核密度等有非常显著的影响.     

EACVD摆动衬底空间流场有限元模拟研究

根据EACVD系统的实际几何特点和工艺参数建立了该系统的三维流场有限元模型,研究了衬底温度及摆动周期、热丝参数、进气口参数对衬底表面流场均匀性的影响.结果表明:衬底低速摆动情况下摆动周期的变化对衬底表面流场的分布没有影响,衬底温度,热丝参数,进气口参数对衬底表面流场都有一定的影响,其中,热丝的排列方式以及进气口气体流量对衬底表面流场的影响最大.最后,采用一组优化的沉积参数进行金刚石膜衬底表面流场的仿真计算,结果表明:采用优化的沉积参数可以使衬底表面气体流速和流场的均匀性都得到很大提高,此研究结果为制备高质量金刚石膜提供理论依据.     

纳米晶粒多晶Si薄膜的低压化学气相沉积

利用低压化学气相沉积(LPCVD)方法,以充Ar的SiH4作为反应气体源,在覆盖有热生长SiO2层的p-(100)Si衬底上制备了具有均匀分布的纳米晶粒多晶Si膜(nc-poly-Si).采用扫描电子显微镜(SEM)、原子力显微镜(AFM)和拉曼谱等检测手段,测量和分析了沉积膜层的表面形貌、晶粒尺寸与密度分布等结构特征.结果表明,nc-poly-v膜中Si晶粒的尺寸大小和密度分布强烈依赖于衬底温度、SiH4浓度与反应气压等工艺参数.典型实验条件下生长的Si纳米晶粒形状为半球状,晶粒尺寸约为40nm,密度分布约为4.0×1010cm-2和膜层厚度约为200nm.膜层的沉积机理分析指出,衬底表面上Si原子基团的吸附、迁移、成核与融合等热力学过程支配着nc-poly-Si膜的生长.     

大面积球面金刚石膜的均匀沉积研究

利用直流电弧等离子体喷射法沉积装置在底径65 mm、高5 mm的Mo球面衬底上制备出厚度大于500 μm金刚石膜.用千分尺测量膜径向厚度以判断膜厚均匀性,用SEM观察膜的表面形貌,用拉曼谱仪测量膜的表面纯度,通过分析电镜形貌和拉曼谱峰的分布特点来判断金刚石膜的质量均匀性.结果表明,在优化工艺条件下,直流电弧等离子体喷射法设备可以在球面Mo衬底上生长出厚度和质量都比较均匀的半透光的自支撑球面金刚石厚膜.     

氩氧流量对ZAO薄膜微结构及其光学性能影响

运用射频磁控溅射技术,改变氩氧流量比在玻璃衬底上生长ZnO∶ Al(ZAO)样品,采用XRD、紫外-可见分光光度计对薄膜微结构、厚度及其光学性能表征,结果发现:维持氩流量不变(9 sccm),随着氧流量增加(1～9 sccm),样品XRD峰强减小,半高宽增大,晶粒尺寸减小,薄膜结晶性能变差;而维持氧流量不变(9 sccm),氩流量减小(9～3 sccm),样品XRD峰强增大,半高宽减小,晶粒尺寸变大,结晶性能变好.紫外可见光光谱在400 ～ 900nm波长区间平均透射率差异大(67.9; ～91.1;);在420 ～ 900 nm波长区间平均透光率高且差异小(90.2; ～92.4;).     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

First-principles coexistence simulations of supercooled liquid silicon

We perform first-principles coexistence simulations of the low-density and the high-density phases of supercooled liquid silicon and find a negative slope for the coexisting line in the temperature-pressure plane. Electron density maps and electron-localization function plots of the two phases of silicon show marked differences. The calculated differences suggest more localized electrons in the low-density liquid compared to the high-density liquid, coming from an increased population of covalent bonds, which further explain the calculated negative slope in the two phase coexistence regime. This is consistent with the presence of a pseudo-gap in low-density liquid silicon, absent in the high-density liquid which shows a metallic behavior.     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P₂S₅ in toluene and have been characterized by elemental analysis, IR, ¹H and ³¹P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻: Monoclinic, P2₁/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?⁻³, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻ comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)