氧分压对化学气相沉积法合成ZnO纳米结构形貌的影响

本文利用化学气相沉积(CVD)法在镀有Au(10 nm)膜的单晶Si(100)上制备了ZnO薄膜,并研究了不同的氧分压对ZnO形貌的影响.借助扫描电镜(SEM)、X射线衍射仪(XRD)和透射电子显微镜(TEM)对样品的形貌、结晶质量和晶体生长取向进行了表征.结果表明:当O2分压较小的时候,O2只能与Zn团簇的某些界面发生反应并逐渐结晶生成层状的ZnO微米团簇.当 O2分压较大的时候,ZnO通过二次生长形成由微米柱阵列和表面无序纳米线构成的分层复合结构,并且表面纳米线的密度随着氧分压的增加而增加.高分辨透射电镜(HRTEM)和选取电子衍射(SAED)分析表明,单根纳米线是沿[001]方向生长的ZnO单晶.     

Growth of Nano Crystalline Diamond on Silicon Substrate Using Different Etching Gases by HFCVD

We investigate the effects of etching gases on the synthesis of nano crystalline diamonds grown on silicon substrate at the substrate temperature of 550 oC and the reaction pressure of 4 kPa by hot filament chemical vapor deposition method, in which CH₄ and H₂ act as a source and diluting gases, respectively. N₂, H₂, and NH₃ were used as the etching gases, respectively. Results show that the optimum conditions can be obtained only for the case of H₂ gas. The crystal morphology and crystallinity of the samples have been examined by scanning electron microscopy and X-ray diffraction, respectively.     

直流电弧等离子体CVD金刚石膜中氢杂质研究

运用傅里叶红外光谱(FT-IR)和核反应分析(NRA)对直流电弧等离子体制备的金刚石膜中的氢杂质进行了研究,并通过添加少量空气到反应气体的实验分析了氢杂质的变化.研究结果发现:红外光谱只能检测金刚石膜中的成键氢,其含量随着氮渗入量的增加而增加,并得出2820 cm~(-1)处的吸收是由氮结合的CH基团振动引起的,2832 cm~(-1)处的吸收可能是由金刚石膜特征结构缺陷结合的CH基团振动引起的,而不是氧相关的基团.核反应分析可以检测金刚石膜中的总氢含量,近表面小于50 nm层氢含量变化快,大于50 nm之后氢含量趋于稳定,此值认为是金刚石膜中的总氢含量.     

整体硬质合金铣刀上制备CVD金刚石涂层的系统三维流场研究

本文通过建立整体硬质合金立铣刀上制备CVD金刚石涂层时CVD沉积系统流场的三维模型,研究了进气口分布对该系统流场均匀性的影响,优化了进气口的分布;在仿真的基础上开展了整体硬质合金立铣刀上制备CVD金刚石涂层的验证实验,采用SEM和Raman对制备的CVD金刚石涂层进行了分析测试.结果表明:优化后的流场可以用于制备高质量的CVD金刚石涂层,且批量制备出的在衬底不同位置上的铣刀表面CVD金刚石涂层的质量均匀一致.     

Low-pressure chemical vapor deposition of TaCN films by pyrolysis of ethylamido-tantalum

Thin films of Tantalum nitride (TaN) were deposited from tetra-ethylamido-tantalum (Ta (NEt₂)₄) by low-pressure chemical vapor deposition. Good-quality step coverage is achieved below 400°C, because the deposition rate is determined by the reaction rates on the surface. The film resistivity increases, however, as the substrate temperature decreases. In order to obtain the low resistivity of films deposited at lower temperatures, we have increased the amount of injected H₂ gas during the deposition. The resistivity decreases by the increase in the H₂ gas flow rate, and it is shown that a large amount of H₂ gas injection during the deposition is an effective method for obtaining both low resistivity and high-quality step coverage. The residual carbon concentration in the film is measured to be >10%, on the other hand, the concentration of N less than 1%. The microstructural investigation using transmission electron microscopy (TEM) reveals that crystalline structure of the deposited film has an amorphous phase.     

热丝辅助射频CVD C3N4薄膜

采用热丝辅助射频等离子体增强化学气相沉积(CVD)方法直接在Si(100)衬底上制备了多晶C3N4薄膜.X射线衍射(XRD)测试表明薄膜同时含有α-C3N4和β-C3N4晶相以及未知结构.傅立叶变换红外吸收谱(FTIR)表明薄膜内的C-N, C＝N和 C≡N 键的吸收峰分别位于1237,1625和2191cm-1.利用扫描电子显微镜(SEM)观测到线度约为2μm、横截面为六边形的β-C3N4晶粒.纳米压痕法测得薄膜的硬度最高可达72.66GPa.     

金刚石膜热沉金属化Ti/Ni/Au体系的研究

利用电子束蒸镀实现了Ti/Ni/Au多层膜在CVD金刚石膜上的金属化,并研究了预处理和后处理工艺对多层膜在基底上结合的影响,发现高温预处理对多层膜和基底的结合有明显的改善.参照国标GJB 126-86进行了热循环试验,未发现多层膜从金刚石膜脱落.利用背散射谱研究了Ti/Ni/Au金属化体系在真空中分别加热400℃和500℃,60 min 金属层的热稳定性.结果发现:优化工艺金刚石膜和金属层间的良好结合和稳定性满足金刚石膜热沉应用的要求.     

HFCVD法沉积金刚石薄膜中热丝优化方法

本文探讨了在HFCVD(hot filament chemical vapor deposition)沉积金刚石薄膜中热丝数量、位置等几何参数对温度场和辐射场的影响.利用系统热传递模型和计算机辅助的数值解方法得到了该方法沉积大面积金刚石薄膜中衬底表面温度分布和热辐射能量密度分布.发现金刚石薄膜的均匀性受热辐射能量密度分布影响较大.进一步给出了沉积面积为100mm×100mm的金刚石薄膜的最佳参数.     

Invariant Analysis of Turbulent Pipe Flow

The anisotropy analysis of Lumley provides a useful tool to quantify the degree of anisotropy in turbulent flows. Also included in the analysis are relations which may be used to check if the flow is axisymmetric or two-dimensional. However, the method does not provide any scale information about the structures. The analysis has therefore been extended here to Fourier space, which allows scale information to be derived. The method was applied to fully developed pipe flow and it was shown that the large-scale motion is everywhere close to axisymmetric. The intermediate scales are strongly influenced by the restrictions posed by the pipe walls. At the centre line, the flow structure appears axisymmetric at all scales, but the measurement sindicate that true axisymmetry is lost very quickly away from the centre line. The structure of the smallest scales could not be determined reliably due to a singularity in the analysis which develops as the scales go to zero. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hot electrons generated by ultra-short pulse laser interacting with solid targets

Hot electrons produced by ultra-short pulse laser interacting with solid targets were studied systematically. When 800 nm, 8 × 10¹⁵ W/cm² laser pulses interacted with solid targets, hot electron emission was found to be collimated in certain directions and the angular distribution of hot electrons depended on the energy absorption. The angular divergence of outgoing hot electrons was inversely proportional to the hot electron energy. The energy spectrum of hot electrons was found to be in a biMaxwellian distribution and the maximum energy was over 500 keV.