Effect of oxygen on regulation of properties of moderately boron-doped diamond films

Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B₃O and B₄O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.     

Relationship between the spatial position of the seed and growth mode for single-crystal diamond grown with an enclosed-type holder

The relationship between the spatial position of the diamond seed and growth mode is investigated with an enclosed-type holder for single-crystal diamond growth using the microwave plasma chemical vapor deposition epitaxial method. The results demonstrate that there are three main regions by varying the spatial position of the seed. Due to the plasma concentration occurring at the seed edge, a larger depth is beneficial to transfer the plasma to the holder surface and suppress the polycrystalline diamond rim around the seed edge. However, the plasma density at the edge decreases drastically when the depth is too large, resulting in the growth of a vicinal grain plane and the reduction of surface area. By adopting an appropriate spatial location, the size of single-crystal diamond can be increased from 7 mm × 7 mm × 0.35 mm to 8.6 mm × 8.6 mm × 2.8 mm without the polycrystalline diamond rim.     

单颗金刚石切削无氧铜的声发射关联维特征*

声发射技术可以实现无氧铜切削加工特征的监测与评价。采用声发射技术监测单颗金刚石磨粒旋转切削无氧铜，利用G-P算法重构出声发射时域信号相空间，采用自相关函数法计算出相空间时间延迟参数，通过相空间双对数曲线的计算，得到不同切削工况下的关联维数。研究结果表明，进给速度和切削速度对声发射信号影响较不显著，切深与声发射信号振幅呈正效应关系；声发射信号双对数曲线呈现阶段性增加趋势，并逐渐收敛于饱和状态，关联维数随着嵌入维数的增加先快速下降后趋于平稳；金刚石切削无氧铜的声发射信号具有混沌运动变化特性，在较小嵌入维数时，关联维数与切深和切削速度呈现线性负效应关系，与进给速度呈现线性正效应关系。该研究为无氧铜的切削加工提供理论参考。     

Developments of nano-polycrystalline diamond anvil cells for neutron diffraction experiments

ABSTRACT

A new high pressure cell for neutron diffraction experiments using nano-polycrystalline anvils is presented. The cell design, off-line pressure generation tests and a gas-loading procedure for this cell are described. The performance is illustrated by powder neutron diffraction patterns of ice VII to ～82?GPa. We also demonstrate the feasibility of single crystal neutron diffraction experiments of Fe₃O₄ at ambient conditions using this cell and discuss the current limitation and future developments.     

Synthesis of nano-polycrystalline diamond from glassy carbon at pressures up to 25 GPa

ABSTRACT

Nano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25?GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ～1700°C at 15?GPa to ～1900°C at 25?GPa. The NPD having grain sizes less than ～50?nm was synthesized at temperatures below ～2000°C at 15?GPa and ～2300°C at 25?GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10?nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions.     

甲烷浓度对碳化硅基底金刚石薄膜摩擦性能影响

利用热丝化学气相沉积法(HFCVD)在碳化硅基底上制备金刚石薄膜,采用场发射扫描电子显微镜、拉曼光谱仪、原子力显微镜研究了在不同甲烷浓度条件下制备的金刚石薄膜表面形貌及物相组成,在干摩擦条件下通过往复式摩擦磨损实验测试并计算了已制备金刚石薄膜的摩擦系数和磨损率,结合物相分析及摩擦磨损实验结果分析了甲烷浓度的改变对金刚石薄膜摩擦磨损性能的影响。结果表明,由于甲烷气体含量的升高,金刚石薄膜结晶质量下降,薄膜由微米晶向纳米晶转变。摩擦磨损实验结果显示:3%甲烷浓度条件下制备的金刚石薄膜耐磨性较好,磨损率为2.2×10^-7 mm³/mN;5%甲烷浓度条件下制备的金刚石薄膜摩擦系数最低(0.032),磨损率为5.7×10^-7 mm³/mN,制备的金刚石薄膜的耐磨损性能相比于碳化硅基底(磨损率为9.89×10^-5 mm³/mN)提升了两个数量级,显著提高了碳化硅基底的耐磨性。     

Preparation and Characterisation of a Bis-μ-Hydroxo-NiIII2 Complex

Hydroxide-bridged high-valent oxidants have been implicated as the active oxidants in methane monooxygenases and other oxidases that employ bimetallic clusters in their active site. To understand the properties of such species, bis-μ-hydroxo-Ni^II₂ complex ( 1 ) supported by a new dicarboxamidate ligand (N,N′-bis(2,6-dimethyl-phenyl)-2,2-dimethylmalonamide) was prepared. Complex 1 contained a diamond core made up of two Ni^II ions and two bridging hydroxide ligands. Titration of the 1 e⁻ oxidant (NH₄)₂[Ce^IV(NO₃)₆] with 1 at −45 °C showed the formation of the high-valent species 2 and 3 , containing Ni^IINi^III and Ni^III₂ diamond cores, respectively, maintaining the bis-μ-hydroxide core. Both complexes were characterised using electron paramagnetic resonance, X-ray absorption, and electronic absorption spectroscopies. Density functional theory computations supported the spectroscopic assignments. Oxidation reactivity studies showed that bis-μ-hydroxide-Ni^III₂ 3 was capable of oxidizing substrates at −45 °C at rates greater than that of the most reactive bis-μ-oxo-Ni^III complexes reported to date.     

以磷化铁为添加剂沿(111)面生长磷掺杂金刚石大单晶

掺杂是调控金刚石性能的一种重要手段。本文采用温度梯度法,在5.6 GPa、1 312 ℃的条件下,选用Fe₃P作为磷源进行磷掺杂金刚石大单晶的合成。金刚石样品的显微光学照片表明,随着Fe₃P添加比例的增加,金刚石晶体的颜色逐渐变深,包裹体数量逐渐增加,晶形由板状转变为塔状直至骸晶。金刚石晶形的变化表明Fe₃P的添加使生长金刚石的V形区向右偏移,这是Fe₃P改变触媒特性的缘故。红外光谱分析表明,Fe₃P的添加使金刚石晶体中氮含量上升,这说明磷的进入诱使氮原子更容易进入金刚石晶格中。激光拉曼光谱测试表明,随着Fe₃P添加比例的增加,所合成的掺磷金刚石的拉曼峰位变化不大,其半峰全宽(FWHM)值变大,这说明磷的进入使得金刚石晶格畸变增加。XPS测试结果显示,随着Fe₃P添加比例的增加,金刚石晶体中磷相对碳的原子百分含量也会增加,这意味着添加Fe₃P所合成的金刚石晶体中有磷存在。     

中国战略性新兴产业国际竞争力评价

以"新钻石模型"为基础,从产业环境、产业支撑和产业创新等3个维度构建战略性新兴产业国际竞争力评价指标体系.运用2005~2014年的面板数据对战略性新兴产业进行因子分析.评价结果显示,电子及通信设备制造业与医药制造业国际竞争力明显高于计算机及办公设备制造业与医疗仪器设备及仪器仪表制造业.航空航天器及设备制造业国际竞争力有很大提升潜力.电子及通信设备制造业创新能力表现突出,但战略性新兴产业整体创新能力较低.     

金刚石纳米线氮空位色心的表面与尺寸效应

使用大规模自旋极化密度泛函理论计算研究了表面修饰和尺寸对金刚石纳米线(DNs)中氮空位(NV)色心的几何结构、 电子结构、 磁性和稳定性的影响. 理论上设计了几种不同的DNs, 这些DNs具有不同的表面修饰(干净、 氢化和氟化), 并且直径达数百个原子. 实验结果证明, 中性(NV⁰)和带1个负电荷(NV^-)的NV色心的电子结构不受半导体表面修饰和DNs直径大小的影响, 但NV色心的稳定性对这两个因素具有不同的响应. 此外, 研究中还发现, 由于DNs中存在圆柱形表面电偶极子层, 对DNs中掺杂的NV^-色心的稳定性, 表面改性诱导了不依赖尺寸的长程效应. 特别地, 对于n型氟化金刚石表面, 掺杂在DN中的NV^-色心可以稳定存在, 而对于p型氢化表面, NV⁰则相对更稳定. 因此, 表面修饰为控制金刚石纳米线中的NV色心的电子结构和稳定性提供了一种精确有效的调控方法.