压力对纳米金刚石膜生长的影响

纳米金刚石膜具有高耐磨能力和低摩擦系数,在多个领域有广阔的应用前景。纳米金刚石膜可通过热丝化学气相沉积方法进行制备。其中,系统压力是关键的参数,适当的压力下可生长纳米金刚石膜,而改变压力则金刚石膜的表面形态将发生变化。实验通过不同压力下制备金刚石膜,采用扫描电镜进行形貌观察,并通过拉曼光谱确定纳米金刚石结构。实验表明,金刚石膜形态随压力变化而改变,一定压力下生长出纳米金刚石膜,降低压力则晶体颗粒变粗。分析其原因是与氢原子的运动密切相关。     

压力对纳米金刚石膜生长的影响（英文）

纳米金刚石膜具有高耐磨能力和低摩擦系数,在多个领域有广阔的应用前景。纳米金刚石膜可通过热丝化学气相沉积方法进行制备。其中,系统压力是关键的参数,适当的压力下可生长纳米金刚石膜,而改变压力则金刚石膜的表面形态将发生变化。实验通过不同压力下制备金刚石膜,采用扫描电镜进行形貌观察,并通过拉曼光谱确定纳米金刚石结构。实验表明,金刚石膜形态随压力变化而改变,一定压力下生长出纳米金刚石膜,降低压力则晶体颗粒变粗。分析其原因是与氢原子的运动密切相关。     

脉冲高能量密度等离子体法类金刚石膜的制备及分析

利用脉冲高能量密度等离子体法在光学玻璃衬底上、在室温下成功的制备了光滑、致密、均匀的纳米类金刚石膜.工艺研究表明：放电电压和放电距离以及工作气体种类对纳米类金刚石膜的沉积起着关键作用.利用拉曼光谱、扫描电镜以及电子能量损失谱分析薄膜的形态结构表明：薄膜具有典型的类金刚石特征；纳米类金刚石膜的晶粒尺寸小于20nm甚至为非晶态；类金刚石膜中含有一定量的氮原子，随着沉积能量的升高，氮的含量增大.纳米类金刚石膜的薄膜电阻超过109Ω/cm2.对放电溅射过程进行了理论分析，结果与工艺研究的结论吻合.     

金刚石锥阵列的无掩膜刻蚀制备及其形貌演变机制

为获得具有优良场发射性能的金刚石锥阵列,利用偏压热灯丝化学气相沉积系统分别在高质量大颗粒金刚石厚膜与纳米金刚石薄膜上进行了无掩膜刻蚀研究,系统比较了高质量大颗粒金刚石厚膜与纳米金刚石薄膜的刻蚀特性,制备了大面积均匀金刚石锥阵列和高长径比(20∶1)金刚石纳米线阵列,探讨了金刚石锥的刻蚀形成机理。     

飞秒激光制备硅窗口增透保护类金刚石膜

采用飞秒激光(800 nm,120 fs,3 W,1 000 Hz)制备类金刚石膜,研究了不同偏压、生长温度和氧气氛等辅助手段对激光沉积类金刚石膜的影响,实验发现在室温(25℃)、无偏压和低气压氧气氛(2 Pa)条件下沉积的类金刚石膜性能最优。在单面预镀普通增透膜的硅红外窗口材料上镀制出了无氢类金刚石膜,3~5μm波段平均透过率达到90%以上,纳米硬度高达40 GPa,用压力为9.8 N的橡皮磨头,摩擦105次,膜层未见磨损,并且通过了军标规定的高温、低温、湿热、盐雾等环境试验,所制类金刚石膜可对红外窗口起到较好的增透保护作用。     

含氢碳膜的生长机制: 分子动力学模拟研究低能量CH基团的作用

探索等离子增强化学气相沉积(PECVD)技术中含氢碳膜的生长机理, 制备出常态超润滑含氢碳膜是表面工程技术领域的目标之一. 基于REBO势函数, 采用分子动力学模拟方法, 通过对比研究CH基团在清洁金刚石和吸氢金刚石表面的沉积行为, 发现低能量CH基团在清洁金刚石(111)面上的吸附效率大于98%, 而在吸氢金刚石(111)面上的吸附效率低于1%. 结果表明PECVD法制备含氢碳膜时, 低能量CH基团对薄膜生长的贡献主要来自于其在表面非饱和C位置的选择性吸附.     

乙炔气体流量对纳米TiC类金刚石复合膜的化学结构及力学性能影响

采用离子注入与反应磁控溅射相结合的方法在钛合金及硅片基体表面上制备了纳米TiC类金刚石(DLC)复合膜.通过纳米压痕技术检测了薄膜的纳米硬度，显微划痕试验评估了薄膜的结合力.通过X射线光电子能谱及X射线衍射表征了薄膜的化学结构.结果表明，通过改变C₂H₂气体流量，可以达到控制薄膜中钛原子含量的目的，合适的C₂H₂气体流量可以在DLC膜中形成较多的纳米TiC晶粒，形成DLC包覆TiC晶粒的复合结构，使DLC膜力学性能得到明显提高.另外，划痕试验表明掺钛、先注入后沉积工艺都使薄膜的结合力得到了较大提高. 关键词： 纳米TiC类金刚石复合膜 类金刚石膜 力学性能     

氢的强化刻蚀对金刚石薄膜品质的影响与sp2杂化碳原子的存在形态

用化学气相沉积方法制备了金刚石薄膜.在制备过程中，通过间歇式关闭甲烷气体，强化了氢对sp2杂化碳原子的刻蚀.用拉曼光谱和金相显微镜对薄膜进行了分析表征.结果表明，氢对sp2杂化碳原子的强化刻蚀并未影响金刚石薄膜的品质和微观结构.这一结论说明，在金刚石薄膜中，sp2杂化碳原子主要存在于金刚石晶粒表面和晶界碳原子之间,而不是以石墨或无定形碳颗粒为主要存在方式. 关键词： 化学气相沉积 金刚石薄膜 拉曼光谱 强化刻蚀     

钛基底的纳米金刚石掺混纳米碳管的场发射特性

在纳米金刚石场发射的基础上, 研究了纳米金刚石掺混纳米碳管的场发射特性。采用电泳沉积法形成了纳米金刚石与纳米碳管的复合涂层, 经热处理后制备出阴极样品, 然后进行微观表征, 再进行场发射特性测试与发光测试。结果表明, 与未掺混的纳米金刚石阴极样品相比, 复合涂层阴极样品的场发射开启电场明显减小, 场发射电流提高, 在较低的电场下阳极表面荧光粉就可以发光, 但发光不均匀, 出现了"边沿发光"的现象。分析了纳米金刚石掺混纳米碳管场发射性能提高的机理, 是由于纳米碳管掺入之后, 涂层的电子输运能力得到增强, 涂层中有效发射体的数目增加。最后, 解释了"边沿发光"现象的成因。     

不同织构CVD金刚石膜的Hall效应特性

采用热丝化学气相沉积法在p型硅衬底上制备了不同织构的多晶金刚石膜,使用XRD表征了CVD金刚石膜的结构特征, 研究了退火后不同织构金刚石膜的电流特性, 使用Hall效应检测仪研究了金刚石膜的霍尔效应特性及随温度变化的规律, 结果表明所制备的金刚石膜是p型材料, 载流子浓度随着温度的降低而增加, 迁移率随着温度的降低而减小. 室温下[100]织构金刚石薄膜的载流子浓度和迁移率分别为4.3×10⁴ cm^-3和76.5 cm²/V·s.     

退火温度对硼掺杂纳米金刚石薄膜微结构和p型导电性能的影响

采用热丝化学气相沉积法制备硼掺杂纳米金刚石 (BDND) 薄膜, 并对薄膜进行真空退火处理, 系统研究退火温度对BDND薄膜微结构和电学性能的影响. Hall效应测试结果表明掺B浓度为5000 ppm (NHB) 的样品的电阻率较掺B浓度为500 ppm (NLB) 的样品的低, 载流子浓度高, Hall迁移率下降. 1000 ℃退火后, NLB和NHB 样品的迁移率分别为53.3和39.3 cm²·V^-1·s^-1, 薄膜的迁移率较未退火样品提高, 电阻率降低. 高分辨透射电镜、紫外和可见光拉曼光谱测试结果表明, NLB样品的金刚石相含量较NHB样品高, 高的硼掺杂浓度使薄膜中的金刚石晶粒产生较大的晶格畸变. 经1000 ℃退火后, NLB和NHB薄膜中纳米金刚石相含量较未退火时增大, 说明薄膜中部分非晶碳转变为金刚石相, 为晶界上B扩散到纳米金刚石晶粒中提供了机会, 使得纳米金刚石晶粒中B浓度提高, 增强纳米金刚石晶粒的导电能力, 提高薄膜电学性能. 1000 ℃退火能够恢复纳米金刚石晶粒的晶格完整性, 减小由掺杂引起的内应力, 从而提高薄膜的电学性能. 可见光Raman光谱测试结果表明, 1000℃退火后, Raman谱图中反式聚乙炔 (TPA) 的1140 cm^-1峰消失, 此时薄膜电学性能较好, 说明TPA减少有利于提高薄膜的电学性能. 退火后金刚石相含量的增大、金刚石晶粒的完整性提高及TPA含量的大量减少有利于提高薄膜的电学性能. 关键词： 硼掺杂纳米金刚石薄膜 退火 微结构 电学性能     

退火时间对硼掺杂纳米金刚石薄膜微结构和电化学性能的影响

采用高分辨透射电镜、紫外和可见光Raman光谱及循环伏安法研究了1000 ℃下退火不同时间的硼掺杂纳米金刚石薄膜的微结构和电化学性能. 结果表明,随退火时间的延长,薄膜中纳米金刚石晶粒尺寸逐渐减小.当退火时间为0.5 h时, 金刚石晶粒尺寸由未退火样品的约15 nm减小为约8 nm, 金刚石相含量增加;当退火时间为2.0 h时,金刚石晶粒减小为2—3 nm, 此时晶界增多,金刚石相含量减少;退火时间为2.5 h时纳米金刚石晶粒尺寸和金刚石相含量又略有上升.晶粒尺寸和金刚石相含量的变化表明薄膜在退火过程中发生了金刚石和非晶碳相的相互转变.可见光Raman光谱测试结果表明,不同退火时间下, G峰位置变化趋势与I_D/I_G值变化一致,说明薄膜内sp²碳团簇较大时, 非晶石墨相的有序化程度较高.退火0.5, 1.0, 1.5和2.0 h时, 电极表面进行准可逆电化学反应,而未退火和退火时间为2.5 h时电极表面进行不可逆电化学反应.退火有利于提高薄膜电极的传质效率, 退火0.5 h时薄膜电极的传质效率最高,催化氧化性能最好.较小的晶粒尺寸、 较高的金刚石相含量以及纳米金刚石晶粒的均匀分布有利于提高电极表面反应的可逆性和催化氧化性能.     

炸药爆轰合成纳米金刚石的拉曼光谱和红外光谱研究

用负氧平衡炸药爆轰法合成纳米金刚石,并用粉末X射线衍射(XRD)仪、激光Raman光谱仪和红外光谱仪等分析仪器对其结构进行表征。XRD结果表明,纳米金刚石为立方结构,由于其内部结构的高密度缺陷、杂质原子的夹杂使谱线偏离,晶格常数比静压合成的大颗粒金刚石大0.72%。由于金刚石晶粒细小,Raman光谱特征峰产生宽化,并且向小波数方向偏移了3 cm-1,此外在纳米金刚石中还含有极少量的石墨。红外光谱测试结果中,3 422 cm-1吸收峰为O—H伸缩振动峰;在1 634 cm-1出现了H₂O的弯曲振动峰,表明在纳米金刚石样品粉末中含有水分;2 930和2 857 cm-1是CH₂的反对称和对称伸缩振动吸收峰;2 971 cm-1是CH₃的反对称伸缩振动吸收峰,说明样品中存在极少量的碳氢化合物;1 788 cm-1吸收峰为CO伸缩振动吸收峰。文章从纳米金刚石的生成机理上分析了产生这些峰位的原因,结果表明纳米金刚石属于Ⅰ型金刚石,在它之中含有ⅠaA型和Ⅰb型金刚石,ⅠaA型金刚石的含量比Ⅰb型金刚石多。     

用X射线衍射强度测定纳米金刚石的德拜特征温度和熔点

 采用陆学善、梁敬魁提出的方法，利用纳米金刚石的X射线衍射强度，计算出它的德拜特征温度为411.7 K，比高温高压合成出的大颗粒金刚石单晶的德拜特征温度（2 200 K）低了许多；且其原子晶格振动的振幅比高温高压合成得到的大颗粒金刚石单晶原子的振幅增大了4.37倍；用Lindemann公式计算出纳米金刚石的熔点为2 070 K，约为高温高压合成出的大颗粒金刚石单晶熔点（4 400 K）的一半。这将导致纳米金刚石原子间结合力的减弱，势必造成其活性的增大，从而引起物理、化学性能的改变。     

Heteroepitaxial growth of cubic boron nitride films on single-crystalline (001) diamond substrates

Heteroepitaxial cubic boron nitride (c-BN) films of significantly improved crystalline quality have successfully been deposited on (001) diamond single crystals using an ion beam assisted preparation method. The results of various characterization techniques prove that films containing 100% pure c-BN phase were nucleated directly on top of diamond without any intermediate hexagonal BN layer. Epitaxially grown, 500-nm-thick c-BN films are mechanically stable even under ambient conditions, though they still exhibit a compressive stress of 5 GPa. Their rocking angles of 0.2°, as observed by X-ray diffraction, point to a hitherto unprecedented quality of the films. Their surface smoothness, the magnitude of their Youngs modulus as well as their ultrahardness corroborate the outstanding quality of these epitaxially grown c-BN films on single-crystalline diamond. PACS 68.55.Jk; 81.15.Jj; 62.20.Qp; 81.05.Je     

Effect of metal nanoparticle doping concentration on surface morphology and field emission properties of nano-diamond films

Nano-diamond particles are co-deposited on Ti substrates with metal (Ti/Ni) nanoparticles (NPs) by the electrophoretic deposition (EPD) method combined with a furnace annealing at 800℃ under N₂ atmosphere. Modifications of structural and electron field emission (EFE) properties of the metal-doped films are investigated with different metal NPs concentrations. Our results show that the surface characteristics and EFE performances of the samples are first enhanced and then reduced with metal NPs concentration increasing. Both the Ti-doped and Ni-doped nano-diamond composite films exhibit optimal EFE and microstructural performances when the doping quantity is 5 mg. Remarkably enhanced EFE properties with a low turn-on field of 1.38 V/μm and a high current density of 1.32 mA/cm² at an applied field of 2.94 V/μm are achieved for Ni-doped nano-diamond films, and are superior to those for Ti-doped ones. The enhancement of the EFE properties for the Ti-doped films results from the formation of the TiC-network after annealing. However, the doping of electron-rich Ni NPs and formation of high conductive graphitic phase are considered to be the factor, which results in marvelous EFE properties for these Ni-doped nano-diamond films.     

纳米金刚石薄膜的二次电子发射特性

 简要介绍了微波等离子体化学气相沉积（MPCVD）方法在硅基底上制备纳米金刚石薄膜的过程,并对制备的薄膜进行了表面分析。在此基础上设计出了用来测定反射型二次电子发射系数的实验装置,得出了几种薄膜在不同入射能量下的发射系数,取得了二次发射系数为15的满意结果,表明纳米金刚石薄膜作为二次电子发射材料具有很好的应用前景。     

Hopping conductivity in C-implanted amorphous diamond,or how to ruin a perfectly good diamond

The electrical properties of amorphous diamond layers produced by C implantation are similar to those of deposited amorphous carbon films. This suggests that amorphous C consists of a mixture of diamond and graphite bonds irrespective of the preparation method.     

Application of printed nanocrystalline diamond film for electron emission cathode

The low-cost and large area screen-printed nano-diamond film (NDF) for electronic emission was fabricated. The edges and corners of nanocrystalline diamond are natural field-emitters. The nano-diamond paste for screen-printing was fabricated of mixing nano-graphite and other inorganic or organic vehicles. Through enough disperse in isopropyl alcohol by ultrasonic nano-diamond paste was screen-printed on the substrates to form NDF. SEM images showed that the surface morphology of NDF was improved, and the nano-diamond emitters were exposed from NDF through the special thermal-sintering technique and post-treatment process. The field emission characteristics of NDF were measured under all conditions with 10⁻⁶ Pa pressure. The results indicated that the field emission stability and emission uniformity of NDF were improved through hydrogen plasma post-treatment process. The turn-on field decreased from 1.60 V/μm to 1.25 V/μm. The screen-printed NDF can be applied to the displays electronic emission cathode for low-cost outdoor in large area.     

Microstructure and tribological performance of self-lubricating diamond/tetrahedral amorphous carbon composite film

In order to smooth the rough surface and further improve the wear-resistance of coarse chemical vapor deposition diamond films, diamond/tetrahedral amorphous carbon composite films were synthesized by a two-step preparation technique including hot-filament chemical vapor deposition for polycrystalline diamond (PCD) and subsequent filtered cathodic vacuum arc growth for tetrahedral amorphous carbon (ta-C). The microstructure and tribological performance of the composite films were investigated by means of various characterization techniques. The results indicated that the composite films consisted of a thick well-grained diamond base layer with a thickness up to 150 μm and a thin covering ta-C layer with a thickness of about 0.3 μm, and sp³-C fraction up to 73.93%. Deposition of a smooth ta-C film on coarse polycrystalline diamond films was proved to be an effective tool to lower the surface roughness of the polycrystalline diamond film. The wear-resistance of the diamond film was also enhanced by the self-lubricating effect of the covering ta-C film due to graphitic phase transformation. Under dry pin-on-disk wear test against Si₃N₄ ball, the friction coefficients of the composite films were much lower than that of the single PCD film. An extremely low friction coefficient (∼0.05) was achieved for the PCD/ta-C composite film. Moreover, the addition of Ti interlayer between the ta-C and the PCD layers can further reduce the surface roughness of the composite film. The main wear mechanism of the composite films was abrasive wear.