Pinhole defects in MPCVD diamond films

Diamond films were deposited in microwave plasma chemical vapor deposition (MPCVD) method on plain silicon substrates with (100) orientation. And the pinhole defects on them were investigated by optical microscopy and scanning electron microscopy (SEM). X-ray masks were fabricated with the films deposited by us. We found the pinhole defects in the film destroyed the gold absorber. The corrosion-resistance tests conducted in 30% KOH solution under 80℃showed that the diamond films with pinhole defects have lower corrosion-resistance. In addition, the possible mechanism of the formation of pinhole defects in diamond films was discussed. And we deduced that the defects on substrates, competitive growth of multi-phase in diamond films, lattice dislocation between substrates and diamond films could be associated with the defect formation.     

Pinhole defects in MPCVD diamond films

Diamond films were deposited in microwave plasma chemical vapor deposition(MPCVD)method on plainsilicon substrates with(100)orientation.And the pinhole defects on them were investigated by opticalmicroscopy and scanning electron microscopy(SEM).X-ray masks were fabricated with the films depositedby us.We found the pinhole defects in the film destroyed the gold absorber.The corrosion-resistance testsconducted in 30% KOH solution under 80℃ showed that the diamond films with pinhole defects have lowercorrosion-resistance.In addition,the possible mechanism of the formation of pinhole defects in diamondfilms was discussed.And we deduced that the defects on substrates,competitive growth of multi-phasein diamond films,lattice dislocation between substrates and diamond films could be associated with thedefect formation.     

GROWTH CHARACTERISTICS OF DIAMOND FILMS DEPOSITED ON Si AND W SUBSTRATES

Growth characteristics of diamond films synthesized by using a dc arc discharge plasma CVD were studied by means of XRD,SEM and reflection electron diffraction. The results showed that columnar growth of the diamond films was observed, the columns having an average diameter of about 15μm, with sharp and regular base edges. Diamond grains grows on the substrata were initially of uniform polygons. An interfacial transition layer of polycrystalline SiC was observed between the diamond film and Si substrate. Diamond grains grown during the early-stage on W substrate were also uniform, and an interfacial transition layer of polycrystalline WC was observed between the diamond film and the substrate.     

Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy （HRTEM）, x-ray diffraction （XRD） and Ftaman spectra, respectively. The nanocrystalline grains are averagely with 80hm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses （100） dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.     

Dynamic scaling and optical properties of Zn（S,O, OH） thin film grown by chemical bath deposition

The scaling behavior and optical properties of Zn(S, O and OH) thin films deposited on soda-lime glass substrates by chemical bath deposition method were studied by combined roughness measurements, scanning electron microscopy and optical properties measurement. From the scaling behaviour, the value of growth scaling exponent β , 0.38±0.06, was determined. This value indicated that the Zn(S, O, OH) film growth in the heterogeneous process was influenced by the surface diffusion and shadowing effect. Results of the optical properties measurements disclosed that the transmittance of the film was in the region of 70%-88% and the optical properties of the film grown for 40 min were better than those grown under other conditions. The energy band gap of the film deposited with 40 min was around 3.63 eV.     

Structures and local ferroelectric polarization switching properties of orthorhombic YFeO_3 thin film prepared by a sol–gel method

Orthorhombic YFeO_3 thin film was prepared on La_(0.67)Sr_(0.33)MnO_3/LaAlO_3 substrate by a sol-gel spin-coating method. The structures of the YFeO_3/La_(0.67)Sr_(0.33)MnO_3/LaAlO_3(YFO/LSMO/LAO) sample were detected by x-ray diffraction pattern, Raman spectrometer, scanning electron microscopy, and atomic force microscope. The local ferroelectric polarization switching properties of the orthorhombic YFO film were confirmed by piezoresponse force microscopy(PFM) for the first time. The results show that the YFO film deposited on LSMO/LAO possesses orthorhombic structure,with ultra-fine crystal grains and flat surface. The leakage current of the YFO film is 8.39 × 10~(-4) A·cm~(-2) at 2 V,with its leakage mechanism found to be an ohmic behavior. PFM measurements indicate that the YFO film reveals weak ferroelectricity at room temperature and the local switching behavior of ferroelectric domains has been identified. By local poling experiment, polarization reversal in the orthorhombic YFO film at room temperature was further observed.     

Electroluminescence Spectrum Shift with Switching Behavior of Diamond Thin Films

We report a special phenomenon on switching behaviour and the electroluminescence (EL) spectrum shift of doped diamond thin films. Nitrogen and cerium doped diamond thin tilms were deposited on a silicon substrate by microwave plasma-assisted chemical vapour deposition system and other special teclmiques. An EL device with a three-layer structure of nitrogen doped diamond/cerium doped diamond/Si02 thin films was made. The EL device was driven by a direct-current power supply. Its EL character has been investigated, and a switching behaviour was observed. The EL light emission colour of diamond films changes from yellow (59Onm) to blue (454nm) while the switching behaviour appears.     

OES study of the gas phase during diamond films deposition in high power DC arc plasma jet CVD system

This paper used optical emission spectroscopy (OES) to study the gas phase in high power DC arc plasma jet chemical vapour deposition (CVD) during diamond films growth processes. The results show that all the deposition parameters (methane concentration, substrate temperature, gas flow rate and ratio of H₂/Ar) could strongly influence the gas phase. C₂ is found to be the most sensitive radical to deposition parameters among the radicals in gas phase. Spatially resolved OES implies that a relative high concentration of atomic H exists near the substrate surface, which is beneficial for diamond film growth. The relatively high concentrations of C₂ and CH are correlated with high deposition rate of diamond. In our high deposition rate system, C₂ is presumed to be the main growth radical, and CH is also believed to contribute the diamond deposition.     

Twin diamond Crystals Grown at High Temperature and High Pressure from the Fe-Ni-C System

Twin diamond crystals grown at high temperature and high pressure (HPHT) in the presence of FeNi catalyst have been examined by transmission electron microscopy(TEM).Direct observation by TEM shows that there are a large amount of twins which lie on the {111} planes in the HPHT-grown diamonds.The twins in the diamond may be formed and may extend into the inner crystal from the twin nucleus formed in the nucleation process.The twins can be formed due to the carbon atoms falling mistakenly into positions where a twin crystal can form during diamond growth,or condensation of supersaturated vacancies on the {111} plane.some hexagonal dislocation loops related to supersaturated vacancies are found on the twins.The Moire fringe image reveals that stacking faults terminate on the intersecting twin boundary.This suggests that,at the temperature that the HPHT diamond is grown,the bordering partial has propagated by gliding up to the twin interface,which can be described by the reaction of a Shockley partial dislocation with a twin on the {111} plane.     

Preparation of p—n Junction Diode by B—Doped Diamond Film Grown on Si—Doped c—BN

A heterojunction diode has been fabricated by boron-doped p-type diamond thin film grown epitaxially on a silicon-doped n-type cubic boron nitride bulk crystal using the conventional hot filament chemical vapour deposition method.The ohmic electrode of Ti(50nm)/Mo(100nm)/Au(300nm)for the p-type diamond film and the bulk crystal of the c-BN were deposited by the rf planar magnetron method.Then the device was annealed at 410℃ in air for 1h in order to form ohmic metal alloy,The current-voltage characteristics of the heterojunction diode were measured and the result indicated that the rectification ratio reached 10^5,and the turn-on voltage and the highest current were 7V and 0.36mA,respectively.     

Strength and plastic deformation of polycrystalline diamond composites

ABSTRACT

The use of nanopolycrystalline diamond has allowed a systematic study on deformation of polycrystalline diamond composites (PCDCs). Bulk PCDCs samples containing either Co or SiC as a binding agent were deformed under high pressure and temperature to strains up to 18% at strain rates ～10^?5?s^?1. All samples exhibit strong work hardening. The strength of PCDCs depends on the amount and type of binding agents and is consistently weaker than that of diamond single crystals. The weakening may be due to the binder materials, which play an important role in affecting grain boundary structures. In SiC-based PCDC, significant grain fragmentation occurs. Nearly all grain boundaries are wetted by SiC after large deformation, resulting in lower strength. In Co-based PCDC, the microstructure is dominated by dislocations, deformation twins, and separated grain boundaries. The density of deformation twins increases significantly with strain, with the twin domain width reaching as low as 10–20?nm at 14% strain.     

用表面生长CVD金刚石的石墨合成高压金刚石

 用热灯丝CVD方法在多晶石墨衬底表面制备CVD金刚石颗粒，并用这种石墨在高温高压条件下采用六面顶压机合成出高压金刚石。初步实验结果表明：采用其表面生长CVD金刚石颗粒的石墨合成高压金刚石，可以提高金刚石的转化率和降低合成压力。     

液体中激光烧蚀固体靶制备纳米晶金刚石

 一种独特的方法用来制备纳米晶金刚石，即在丙酮溶液中激光烧蚀石墨靶制备纳米晶金刚石。透射电镜（TEM）和高分辨电镜（HREM）分析表明，所制备的纳米晶金刚石为立方金刚石和六方金刚石晶体。     

Thermodynamic and kinetic study on interfacial reaction and diamond graphitization of Cu Fe-based diamond composite

Cu-Fe based diamond composites used for saw-blade segments are directly fabricated by vacuum and pressure- assisted sintering. The carbide forming elements Cr and Ti are added to improve interfacial bonding between diamond and the Cu-Fe matrix. The interfacial reactions between diamond/graphite and Cr or Ti, and diamond graphitization are investigated by thermodynamics/kinetics analyses and experimental methods. The results show that interfacial reactions and graphitization of diamond can automatically proceed thermodynamically. The Cr3C2 , Cr7C3 , Cr23C6 , and TiC are formed at the interfaces of composites by reactions between diamond and Cr or Ti; diamond graphitization does not occur because of the kinetic difficulty at 1093 K under the pressure of 13 MPa.     

人工合成金刚石研究进展

1796年英国科学家S．Tennant的精确燃烧实验，首次揭示金刚石是由纯碳构成的宝石，从此人类开始了漫长的人工合成金刚石的探索．金刚石通常只能在极端条件下形成，因此，合成技术的突破是人类合成水平提高的一个重要标志，文章对这一领域一些重要工作做了简单回顾，也讨论了作者在合成金刚石方面的工作．我们在440℃的低温条件下，用碱金属(Li，Na，K)还原超临界CO2，得到透明、大尺寸的金刚石晶体，首次实现了金刚石燃烧实验的逆过程，即把低能、直线型CO2分子变成了碳-碳四面体连接的金刚石，开辟了人工合成金刚石的新途径．也讨论了它与天然金刚石起源之间的可能联系．     

The laboratory confirmed natural crystallization of diamond from carbonized organic compounds

Abstract

In the paper the conception of the natural diamond growth as a result of the organic compounds reaction in the presence of noncompensated spin was checked. They might have played the essential role in the nucleation of diamond crystals. In the experiments, the partly carbonized phenolformal-dehyde resin instead of graphite was used as a carbon source. The final result of the process of the diamond growth depended on the temperature of resin carbonization as well as on the temperature and pressure of synthesis. The 3,8 GPa pressure, which is less than needed for graphite to diamond transformation in the classic industrial process, was sufficient to produce transparent and colourles diamond crystal of the size up to 0,7 mm.     

纳米引晶法选择性生长金刚石薄膜

通过传统的光刻工艺和纳米引晶技术,在抛光的单晶Si衬底上形成带有 超细金刚石纳米粉的引晶图案,并利用该图案与抛光Si处金刚石成核密度的巨大差异,实现 金刚石薄膜的高选择比生长。该方法具有工艺简单、沉积效率高、选择比高、对底无任何损 伤等优点。同时,这种方法很容易在不同衬底上实现金刚石薄膜的大面积选择性生长。     

金刚石层厚度对复合片(PDC)残余应力的影响

 通过X射线应力测试和有限元分析相结合的方法,研究了金刚石层厚度对聚晶金刚石复合片（PDC）残余应力的影响,并根据实验测试结果推导出了PDC表面中心与边缘的应力随金刚石层厚度变化的关系式。随着金刚石层厚度由0.5 mm增加到2.0 mm,PDC表面中心的压应力从1 800 MPa下降至700 MPa左右,而边缘部分的应力逐渐由压应力转为拉应力。金刚石层加厚虽然对边缘部分的最大拉应力影响不大,但使PDC边缘拉应力区宽度由0.76 mm增加到了2.85 mm。金刚石层厚度的增加还使得PDC边缘界面附近y方向的最大拉应力和位于界面边缘处的最大剪应力显著加大,这是金刚石层较厚的PDC界面容易产生裂纹的主要原因。     

脉冲激光诱导液-固界面反应合成金刚石纳米晶中的结构相变模型

 探讨了脉冲激光诱导液-固界面反应法（PLIR: Pulsed-Iaser Induced Liquid-Solid Interface Reaction ）制备金刚石纳米晶的物理化学机制,提出了金刚石纳米晶的成核机理,即由激光诱导石墨六方结构原子团过渡到石墨菱方结构、然后转变成立方金刚石晶核,以及由石墨六方结构直接转变成六方金刚石结构的相变模型,并讨论了基于液-固界面反应的纳米晶生长动力学,较好地从动力学上解释了合成金刚石纳米晶的物理化学机制。     

氮氢共掺杂金刚石中氢的典型红外特征峰的表征

所有天然Ia型金刚石红外光谱中都存在3107 cm-1特征峰,而在金属触媒直接合成的金刚石红外光谱中没有检测出3107 cm-1特征峰.本文在6.3 GPa,1500?C条件下,通过Fe70Ni30触媒中添加P3N5直接合成出具有3107 cm-1特征峰的氮氢共掺杂的金刚石.红外光谱分析表明,合成的金刚石中氢有两种存在形式:一种对应着乙烯基团C=CH2中C—H键的伸缩振动(3107 cm-1)和弯曲振动(1450 cm-1)的吸收峰,另一种对应着sp3杂化C—H键的对称伸缩振动(2850 cm-1)和反对称伸缩振动(2920 cm-1)的吸收峰.通过分析发现,3107 cm-1吸收峰与金刚石中聚集态的氮原子有关,当金刚石中没有聚集态的氮元素时,即使氮含量高也不会出现3107 cm-1峰;并且2850和2920 cm-1附近的吸收峰比3107 cm-1附近的吸收峰更为普遍存在.这说明sp3杂化C—H键比乙烯基团的C—H键更广泛存在于金刚石中,从两者的峰值看,天然金刚石中的氢杂质主要以乙烯基团C=CH2存在.3107 cm-1吸收峰与聚集态的氮原子的这种存在关系为天然金刚石形成机制的研究提供了一种新思路,同时较低的合成条件也可能为氢与其他元素共掺杂合成具有n型半导体特性的金刚石提供一个较理想的合成环境.