金刚石薄膜的结构特征对薄膜附着性能的影响

在不同实验条件下，用微波等离子体化学气相沉积设备在硬质合金(WC+6%Co)衬底上沉积了 具有不同结构特征的金刚石薄膜.用Raman谱表征薄膜的品质和应力，用压痕实验表征薄膜的 附着性能，考察了薄膜中sp²杂化碳含量、形核密度、薄膜厚度对薄膜附着性能 的影响.结 果表明：sp²杂化碳的缓冲作用使薄膜中sp²杂化碳的含量对薄膜中 残余应力有较大的影 响，从而使薄膜压痕开裂直径统计性地随sp²杂化碳含量的增加而减小；仅仅依 靠超声遗 留的金刚石晶籽提高形核密度并不能有效改变薄膜与硬质合金基体之间的化学结合状况，从 而不能有效提高薄膜在衬底上的附着性能；在薄膜较薄时，晶粒之间没有压应力的存在，开 裂直径并不明显随厚度增加而增加，只有当薄膜厚度增加到一定值，晶粒之间才有较强压应 力存在，开裂直径随厚度的增加而较为迅速地增加. 关键词： 金刚石薄膜 附着性能 2杂化碳')" href="#">sp²杂化碳 成核密度 薄膜厚度     

非平衡磁控溅射法类金刚石薄膜的制备及分析

利用非平衡磁控溅射物理气相沉积技术制备了光滑、致密、均匀的类金刚石薄膜.分析沉积工艺参数对所得类金刚石薄膜的电学特性的影响以及溅射粒子的大小、能量、碰撞及沉积过程中的相变机理后认为：溅射粒子越小、与环境气体分子的碰撞次数越多、与衬底相互作用时具有适当动量等，能够有效提高薄膜中sp^３杂化碳原子的含量.利用拉曼光谱 、纳米力学探针、红外光谱、扫描电镜等分析了所得类金刚石膜的结构、力学及光学性能、 表面形貌等特征.结果表明，类金刚石膜中sp^３杂化碳原子的含量较高，显微硬 度大于11GPa，薄膜光学透过率达到89.4％，折射系数为1.952，沉积速率为0.724μm/h，表 面光滑、致密、均匀，不存在明显的晶粒特征. 关键词： 非平衡磁控溅射 类金刚石膜 拉曼光谱 红外光谱     

类金刚石薄膜在硅基底上的沉积及其热导率

采用分子动力学方法模拟了碳在晶体硅基底上的沉积过程, 并分析计算了所沉积的类金刚石薄膜的面向及法向热导率. 对沉积过程的模拟表明, 薄膜密度及sp³杂化类型的碳原子所占比例均随沉积高度的增加而减小, 在碳原子以1 eV能量垂直入射的情况下, 在硅基底上沉积的薄膜密度约为2.8 g/cm³, sp³杂化类型的碳原子所占比例约为22%, 均低于碳在金刚石基底上沉积的情况. 采用Green-Kubo方法, 计算了所沉积类金刚石薄膜的热导率, 其面向热导率可以达到相同尺寸规则金刚石晶体的50%左右, 并且随着薄膜密度与sp³杂化类型碳原子所占比例的升高而升高.     

硼/氮原子共掺入金刚石的晶格损伤及其退火过程的计算机模拟

借助于Tersoff势函数和分子动力学模拟技术研究了室温下500eV的能量粒子硼(4个)和氮(8个)共掺入金刚石晶体中所引起的损伤区域内晶体微细观结构的变化特征以及后续加热退火晶体结构的演变特征.结果表明：随着掺入原子数目的增加，受影响的区域范围渐渐增大，12个粒子全部注入金刚石晶体后局部影响区域的半径达0.68nm，损伤区域中心的三配位原子数增加而四配位数原子数量减少.加热退火过程中损伤中心区域的原子发生扩散，部分原子的扩散距离达到4个晶格间距.加热退火使损伤区域中心原子间的平均键长趋于金刚石结构的键长.退火后薄膜中注入的杂质原子向表面扩散引起应力分布产生变化，杂质原子经过一系列的扩散过程能够到达空位的位置，减少薄膜中空位数量，减小晶格畸变程度，原子向表面扩散引起应力产生重新分布，薄膜中应力峰值的峰位向薄膜表面发生移动，局部应力集中程度降低.通过不同退火温度的比较发现低温下退火(800℃)更有利于空位的运动和晶格损伤的恢复从而提高晶格质量. 关键词： 金刚石共掺杂 分子动力学 退火     

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     

单晶硅纳米切削中C–C键断裂对金刚石刀具磨损的影响

本文基于分子动力学方法模拟金刚石刀具纳米切削单晶硅, 从刀具的弹塑性变形、C–C键断裂对碳原子结构的影响以及金刚石刀具的石墨化磨损等方面对金刚石刀具的磨损进行分析, 采用配位数法和6元环法表征刀具上的磨损碳原子. 模拟结果表明: 在纳米切削过程中, 金刚石刀具表层C–C键的断裂使其两端碳原子由sp³杂化转变为sp²杂化, 同时, 表面上的杂化结构发生变化的碳原子与其第一近邻的sp²杂化碳原子所构成的区域发生平整, 由金刚石的立体网状结构转变为石墨的平面结构, 导致金刚石刀具发生磨损; 刀具表面低配位数碳原子的重构使其近邻区域产生扭曲变形, C–C键键能随之减弱, 在高温和高剪切应力的作用下, 极易发生断裂; 在切削刃的棱边上, 由于表面碳原子的配位严重不足, 断开较少的C–C键就可以使表面6 元环中碳原子的配位数都小于4, 导致金刚石刀具发生石墨化磨损.     

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     

类金刚石薄膜力学特性的分子动力学模拟

基于Brenner的REBO势函数,利用分子动力学方法模拟了含氢量不同的类金刚石薄膜的纳米压痕过程,依据得到的加载卸载曲线,计算了薄膜的刚度、硬度以及弹性模量.结果表明:类金刚石薄膜的硬度由氢含量和sp³键含量两个因素共同决定;当薄膜中氢含量小于39% 时,薄膜硬度主要取决于sp³键含量,sp³键越多,硬度越高;当薄膜中氢含量达到52%,薄膜硬度则显著下降,此时氢的作用占据主导地位. 关键词： 类金刚石薄膜 分子动力学模拟 纳米压痕 硬度     

调控硼硫掺杂比实现金刚石n型转变的研究

金刚石半导体由于其特殊的机械性能使其在极端环境下有较广的应用前景. 虽然通过硼(B)元素掺杂较易得到p型金刚石半导体,但具有优异电学性能的n型半导体却鲜见报道. 硼、硫（S）原子因半径及外层电子互补,其协同掺杂易合成p型或n型半导体,但其物理机理尚不清晰.在课题组已有实验报道基础上,借助第一性原理探究了B-S不同比例单掺杂及共掺杂金刚石的形成能、晶体内的存在形式及电子结构,从原子尺度揭示了金刚石由p型向n型半导体转变的阈值掺杂比例. 通过实验与理论的对比发现B在晶格内趋向团聚,而过量的S掺杂则发生析出.     

添加Fe(C5H5)2合成氢掺杂金刚石大单晶及其表征

在Ni₇₀Mn₂₅Co₅-C体系中添加含氢化合物Fe(C₅H₅)₂作为新型氢源, 利用温度梯度法, 在压力为5.5-6.0 GPa、温度为1280-1400 ℃的条件下, 成功合成出氢掺杂的宝石级金刚石大单晶. 通过傅里叶显微红外光谱发现, 随着Fe(C₅H₅)₂添加量的增加, 合成晶体中与氢相关的对应于sp³杂化C-H键的对称伸缩振动和反对称伸缩振动的红外特征峰2850和2920 cm^-1逐渐增强, 而晶体中氮含量却逐渐减少. 通过合成晶体的拉曼光谱分析发现, 金刚石的拉曼峰伴随Fe(C₅H₅)₂的添加向高频偏移, 这表明氢的进入在金刚石内部产生了压应力. 观察扫描电子显微镜图像发现, 在低含量Fe(C₅H₅)₂添加时晶体表面平滑, 而高含量添加时晶体表面缺陷增多, 且呈现出气孔状. 使用新的添加剂Fe(C₅H₅)₂作为氢源, 合成出含氢宝石级金刚石单晶, 丰富了金刚石单晶中对氢的研究内容, 也可为理解天然金刚石的形成机理提供帮助.     

同质与异质外延掺杂CVD金刚石薄膜的结构与性能

采用化学气相沉积(CVD)技术,以高温高压(HTHP)合成的(100)金刚石和p型(100)Si为衬底制备了硫掺杂和硼-硫共掺杂金刚石薄膜,利用原子力显微镜(AFM)、扫描隧道显微镜(STM)及隧道电流谱(CITS)等手段分析同质和异质外延CVD掺杂金刚石薄膜的结构和性能.结果表明:异Si衬底上CVD金刚石的形核密度低,薄膜表面比较粗糙,粗糙度达到18.5nm;同质HTHP金刚石衬底上CVD金刚石薄膜晶粒尺寸约为10—50nm,表面平整,表面粗糙度为1.8nm.拉曼测试和电阻测量的结果显示,在HTHP金刚 关键词： 金刚石 掺杂 外延     

Field emission from nitrogen-implanted CVD diamond film grown on silicon wafer

Nitrogen was implanted into chemical vapor deposition (CVD) diamond films and the electron field emission properties of the nitrogenated diamond films were investigated. Nitrogen implantation was carried out using 10 keV in the dose range from 1×10¹⁶ to 5×10¹⁷ cm^-2 at room temperature. Raman and X-ray photoelectron spectroscopy measurements revealed that nitrogen implantation damaged the structure of the diamond film and promoted the formation of sp² C–C and sp² C–N bondings. Increasing the implantation dose could lower the threshold field of the emission of the diamond film from 18 V/m to 4 V/m. The effective work function of the nitrogen-implanted CVD diamond films was estimated to be in the range of 0.01–0.1 eV. The enhancement of field emission for nitrogen-implanted CVD diamond films was attributed to the increase of the sp² C bonds fraction and the formation of defect bands within the bulk diamond band gap induced by nitrogen implantation, which could alter the work function and elevate the Fermi level. Consequently, the energy barrier for electron tunneling was reduced.     

热灯丝CVD金刚石膜硼掺杂效应研究

利用Ｒａｍａｎ谱和Ｘ射线衍射微分析研究了金刚石膜硼掺杂效应．研究发现，在硼浓度较低时，金刚石膜中非晶碳（Ｓｐ²键合）含量减少，而随着硼浓度增加，金刚石膜的Ｒａｍａｎ特征峰（Ｓｐ^３）向低频方向漂移，并且展宽和出现不对称．这是由于硼掺杂引起晶格变化及Ｆａｎｏ互作用所致 关键词：     

Investigation of properties of Cu containing DLC films produced by PECVD process

Copper containing diamond like carbon (Cu-DLC) thin films were deposited on various substrates at a base pressure of 1×10^?3 Torr using a hybrid system involving DC-sputtering and radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) techniques. The compressive residual stresses of these films were found to be considerably lower, varying between 0.7 and 0.94 GPa and Cu incorporation in these films improve their conductivity significantly. Their structural properties were studied by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction techniques that clearly revealed the presence of Cu in the DLC structure. Raman analysis yields that Cu incorporation in DLC enhances the graphite-like sp² bonding. However, the sp² bonding was found to continuously reduce with the increasing C₂H₂ gas pressure, this may be due to reduction of Cu nanocrystal at the higher pressure. FTIR results inferred various bonding states of carbon with carbon, hydrogen and oxygen. In addition, hydrogen content and sp³ and sp² fractions in different Cu-DLC films were also estimated by FTIR spectra and were correlated with stress, electrical, optical and nano-mechanical properties of Cu-DLC films. The effect of indentation load (4–10 mN) on nano-mechanical properties of these films was also explored.     

Growth and annealing study of hydrogen-doped single diamond crystals under high pressure and high temperature

A series of diamond crystals doped with hydrogen is successfully synthesized using LiH as the hydrogen source in a catalyst-carbon system at a pressure of 6.0 GPa and temperature ranging from 1255 C to 1350 C.It is shown that the high temperature plays a key role in the incorporation of hydrogen atoms during diamond crystallization.Fourier transform infrared micro-spectroscopy reveals that most of the hydrogen atoms in the synthesized diamond are incorporated into the crystal structure as sp 3-CH 2-symmetric(2850 cm-1) and sp 3 CH 2-antisymmetric vibrations(2920 cm-1).The intensities of these peaks increase gradually with an increase in the content of the hydrogen source in the catalyst.The incorporation of hydrogen impurity leads to a significant shift towards higher frequencies of the Raman peak from 1332.06 cm-1 to 1333.05 cm-1 and gives rise to some compressive stress in the diamond crystal lattice.Furthermore,hydrogen to carbon bonds are evident in the annealed diamond,indicating that the bonds that remain throughout the annealing process and the vibration frequencies centred at 2850 and 2920 cm-1 have no observable shift.Therefore,we suggest that the sp 3 C-H bond is rather stable in diamond crystals.     

带隙可调的Al，Mg掺杂ZnO薄膜的制备

利用射频磁控溅射（RF-MS）方法,固定Al₂O₃掺杂量2 wt%,Mg掺杂量分别为1 wt%,3 wt%和5 wt%,在玻璃基底上制备了Al掺杂和Al,Mg共掺杂的ZnO薄膜,在500 ℃空气中退火2 h后,测量并比较了它们的光学和电学性质．结果表明,Al,Mg共掺杂的ZnO薄膜结晶质量良好,具有ZnO纤锌矿结构,具有较强的（002）面衍射峰,表明薄膜晶体沿c轴优先生长;与Al掺杂ZnO薄膜相比蓝端光透射率增加,1 wt%和3 wt% Mg掺杂薄 关键词： 射频磁控溅射 ZnO薄膜 Al Mg共掺杂     

Substitutional phosphorus incorporation in nanocrystalline CVD diamond thin films

Nanocrystalline diamond (NCD) thin films were produced by chemical vapor deposition (CVD) and doped by the addition of phosphine to the gas mixture. The characterization of the films focused on probing the incorporation and distribution of the phosphorus (P) dopants. Electron microscopy evaluated the overall film morphology and revealed the interior structure of the nanosized grains. The homogeneous films with distinct diamond grains featured a notably low sp²:sp³‐ratio as confirmed by Raman spectroscopy. High resolution spectroscopy methods demonstrated a homogeneous P‐incorporation, both in‐depth and in‐plane. The P concentration in the films was determined to be in the order of 10¹⁹ cm^–3 with a significant fraction integrated at substitutional donor sites. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Synthesis of n-type semiconducting diamond film using diphosphorus pentaoxide as the doping source

An n-type semiconducting diamond film has been synthesized by the hot filament CVD method using diphosphorus pentaoxide as the doping source. The obtained film was identified as polycrystalline diamond containing few sp² components by means of several methods including Raman spectroscopy. From measurements of the Hall effect and the Seebeck effect, the film was found to be an n-type semiconductor.Patent pending No. Heisei 1-302209     

Optical and structural properties of polycrystalline CVD diamond films grown on fused silica optical fibres pre-treated by high-power sonication seeding

In this paper, the growth of polycrystalline chemical vapour deposition (CVD) diamond thin films on fused silica optical fibres has been investigated. The research results show that the effective substrate seeding process can lower defect nucleation, and it simultaneously increases surface encapsulation. However, the growth process on glass requires high seeding density. The effects of suspension type and ultrasonic power were the specific objects of investigation. In order to increase the diamond density, glass substrates were seeded using a high-power sonication process. The highest applied power of sonotrode reached 72 W during the performed experiments. The two, most common diamond seeding suspensions were used, i.e. detonation nanodiamond dispersed in (a) dimethyl sulfoxide and (b) deionised water. The CVD diamond nucleation and growth processes were performed using microwave plasma assisted chemical vapour deposition system. Next, the seeding efficiency was determined and compared using the numerical analysis of scanning electron microscopy images. The molecular composition of nucleated diamond was examined with micro-Raman spectroscopy. The sp³/sp² band ratio was calculated using Raman spectra deconvolution method. Thickness, roughness, and optical properties of the nanodiamond films in UV–vis wavelength range were investigated by means of spectroscopic ellipsometry. It has been demonstrated that the high-power sonication process can improve the seeding efficiency on glass substrates. However, it can also cause significant erosion defects at the fibre surface. We believe that the proposed growth method can be effectively applied to manufacture the novel optical fibre sensors. Due to high chemical and mechanical resistance of CVD diamond films, deposition of such films on the sensors is highly desirable. This method enables omitting the deposition of an additional adhesion interlayer at the glass–nanocrystalline interface, and thus potentially increases transmittance of the optical system.