Currently available methods of industrial nanodiamond synthesis

The main theoretical aspects of detonation decomposition of powerful mixed explosives with a negative oxygen balance accompanied by the formation of nanodiamonds (ultrafine-dispersed diamonds, UDDs) are described. The basic UDD synthesis parameters are considered, and the expediency of using trotyl-hexogen alloys is shown. The conditions of diamond phase conservation in the detonation products are specified. Various versions of industrial detonation synthesis of UDDs are considered. The most efficient technology of chemical cleaning of UDDs (with nitric acid at high temperatures and pressures) for producing UDDs with the highest purity is described.

     

Physical-mechanical properties of nanocrystalline materials based on ultrafine-dispersed diamonds

The physical-mechanical properties of polycrystals produced on the basis of ultrafine-dispersed diamonds (UDDs) at high static pressures with the use of thermal treatment in vacuum are investigated. The properties of the polycrystals are shown to depend on the sintering conditions and sintering technique, as well as on the modification of the starting powders. With the addition of metals (Co, Ti) to UDD powders, the mechanical strength of compacts increases, their structure improves, and their parameters can be optimized at lower thermobaric treatment temperatures. By studying the products of thermal treatment of UDDs in vacuum, it is established that the compacts and individual particles that form during thermal treatment differ significantly in microhardness.     

Intercalation of ultrafine-dispersed diamond in aqueous suspensions

A method for preparing ultrafine-dispersed diamond (UDD) powders with a uniform distribution of metal ion impurity over the bulk of a powder is developed. The uniformity and composition of a UDD sample is demonstrated using x-ray diffraction and chemical analysis.     

Shock-wave sintering of nanodiamonds

A two-stage technology of compaction of ultrafine-dispersed diamonds (UDDs) is developed and successfully applied for ampoule-free sintering of dense UDD granules in lead under a pressure of up to 100 GPa. Standard strength tests of polycrystals (fractions 80/63, 125/80) thus obtained showed a wide spread in strength (from grade AS4 to AS80), which is indicative of highly inhomogeneous sintering conditions. A single-crystal diamond is obtained for the first time by using shock-wave compaction; the crystal is a transparent twinned octahedron 0.6 mm in size with an impurity content of less than 0.05%. This result is unexpected and encourages us to believe that this method can be used to manufacture jewellery-grade diamonds (larger than 2 mm in size). The pressure and temperature conditions of sintering are analyzed.     

Nanopolishing of silicon wafers using ultrafine-dispersed diamonds

In the present study, two new methods are proposed for the polishing of silicon wafers using ultrafine-dispersed diamonds (UDDs). The first proposed polishing method uses a polishing tool with an ultrafine abrasive material made through the electrophoretic deposition of UDDs onto a brass rod. Dry polishing tests showed that the surface roughness of the silicon wafer was reduced from R_a=107 to 4 nm after polishing for 30 min. The second method uses a new polishing pad with self-generating porosity. By polishing with the new pad in combination with the polycrystalline UDD in a water suspension, it is possible to achieve the specified surface roughness of the silicon wafer much faster than when using a conventional pad made of foamed polyurethane. The tests showed that the surface roughness of the silicon wafer was reduced from R_a=107 to 2 nm after polishing for 90 min.     

Thermal purification of detonation diamond

Detonation ultradispersed diamonds (UDDs) of different types were comparatively studied by thermogravimetric analysis (TGA) and Raman scattering (RS). The TGA method was used to determine temperature regions corresponding to oxidation of different carbon forms contained by UDD powder. In particular, it was found that heating in air at temperatures above 550°C results in oxidation and removal of nondiamond carbon, while the diamond fraction is retained. The shape of diamond lines in RS spectra of different UDDs oxidized at 550°C showed good agreement with the phonon confinement model. A comparison of the experimental data and theoretical calculations for the RS line shape allowed the determination of crystalline grain sizes in UDDs of different types. The values obtained correspond to the data of manufacturers of nanodiamond powders under study.     

Use of ultrafine-dispersed nanodiamond for selective deposition of boron-doped diamond films

A suspension of ultrafine-dispersed nanodiamond was used for introducing (in particular, selectively) high-density centers of diamond nucleation on various substrates. High-quality doped diamond films to be used as electrochemistry electrodes were deposited from the gas phase in a microwave discharge on certain substrates treated using ultrafine-dispersed nanodiamond. A uniform distribution of nucleation centers with concentrations greater than 10¹⁰ cm^-2 on silicon substrates was obtained. Electrochemical current-potential curves were measured for continuous films. Diamond meshes of different transparency were grown using selective nucleation. Successful production of high-quality doped diamond meshes gives grounds to consider them the most promising electrodes for use in electrochemistry.     

模板对异构体选择性生长的动力学控制作用与化学气相沉积金刚石的生长机理

阐述了模板的动力学控制作用对大尺度有序结构特别是亚稳相的生长，对自由能相差很小的异构体的选择生长所具有的重要作用.汲取现有金刚石生长理论的合理思想，以模板概念为基础给出了对化学气相沉积(CVD)过程的动力学热力学综合描述：1)碳原子在碳氢化合物中的化学势高于固相碳，气相碳氢化合物的碳原子有可能落到化学势较低的固态碳的各种异构体.2)气相碳通过表面反应实现向固相碳的转化.3)表面的模板作用是控制气相碳原子转换方式的主要动力学因素，不同的表面(石墨各种取向的表面及金刚石不同取向的表面)选择了落入其上的碳原子的结构方式及能量状态.4)因此,衬底的不同区域可发生几种不同的独立的表面反应过程,这些反应对应于不同表面的生长.5）而这些表面反应的方向性及速度受表面临域热力学因素的影响，反应的方向性决定了某种晶面是生长或刻蚀，在特定的温度、压强及各种气体分压下可以实现金刚石的生长和石墨的刻蚀.6)衬底局域晶格结构及键价结构和衬底表面气相的温度、压强及各种气体分压等热力学条件共同决定了成核的临界条件.7）与外界有能量和物质交换的等离子体系统，以及气相中发生的一系列化学反应，仅起到了维持某种固相表面生长所需要的非平衡热力学条件和化学条件的作用.金刚石和石墨表面具有的模板动力学控制作用，在特定热力学条件下主导自身外延层的生长方式；异质衬底的某些局域微观结构可以作为新相生长成核的局域模板；不同材料、不同的处理方法、及不同的化学环境下的衬底具有不同的局域微观结构，从而决定了多晶薄膜的取向优势. 关键词： 模板 异构体 选择性生长 金刚石薄膜     

Polishing nanodiamonds

The results of polishing (using suspensions of nanodiamonds (NDs) produced by detonation synthesis at different plants) of the surfaces of 23 solid materials having different chemical compositions, production processes, structure, electronic properties, hardness, reactivity, and application are described. Atomic force microscopy is used to compare the roughness of these surfaces with the surfaces of such materials subjected to polishing with diamond synthetic micropowders (of grades 1/0, 0.25/0, 0.1/0) and to chemical-mechanical polishing (CMP) with amorphous colloid silica. Stable ND suspensions are shown to cause a number of effects, namely, polishing, scratching, plastic flow of surface layers, and CMP. The aggregative state of solid particles is shown to be of importance. Polishing with NDs is found to be accompanied by mechanical nanoscratching, which can be leveled by the introduction of certain etchants into an ND suspension. The use of amorphous nanoparticles is the only technique that does not induce deformation in the surface layer of a material.     

MOCVD法生长SAWF用ZnO/Diamond/Si多层结构

使用等离子体辅助MOCVD系统在金刚石,硅衬底上成功地制备了氧化锌多层薄膜材料,通过两步生长法对薄膜质量进行了优化。XRD测试显示优化后的样品具有c轴的择优取向生长,PL谱测试表明样品经优化后不仅深能级发射峰消失,同时紫外发射峰增强。对优化后的样品的表面测试显示出较低的表面粗糙度。比较氧化锌多层薄膜结构的声表面波频散曲线,ZnO薄膜声表面滤波器受膜厚和衬底材料的影响较大。当ZnO薄膜较薄时,在它上面的传播速度将与衬底上的传播速度接近,与其他衬底上生长的薄膜相比,以金刚石这种快声速材料为衬底的ZnO多层薄膜结构,声表面波滤波器的中心频率将提高1倍左右。     

Detonation diamonds in Ukraine

Some information on the history of dynamic synthesis of diamond in Ukraine is considered. Basic characteristics of ASM5 0.1/0 and ASM1 0.1/0 nanodiamond powders produced by static synthesis are described. The characteristics and surface properties of nanodiamond powders produced by detonation synthesis in Ukraine are presented. It is shown that the chemical activity of the particle surface can be controlled. Applications of nanopowders produced by detonation synthesis in various technologies are considered.     

Novel technique for hetero-epitaxial diamond film growth on cubic boron nitride from iron carbide at high temperature and high pressure

Cubic boron nitride (c-BN) crystals about 0.1–0.3 mmin dimension were treated with iron carbide powders (high purity 99%) with size of 80–100 mesh at a high temperature of 1620 K and a high pressure of 5.2 GPa. It was found that hetero-epitaxial diamond films have been grown on the c-BN from iron carbide. The formation of dia-mond films on the cubic boron nitride can be confirmed by laser Raman spectra, face scan of elements and reflective high-energy electron diffraction. It was suggested that diamond films could be epitaxially formed on the c-BN through decomposition of iron carbide. This approach provides a possible and very effective way to realize hetero-epitaxial growth of homogeneous and large-area diamond films on c-BN, which is different from the conventional technique using a chemical vapor deposition method. Received: 20 December 2000 / Accepted: 9 January 2001 / Published online: 28 February 2001     

Effect of thermal and chemical treatment on the structure and composition of nanodiamonds

The effect of chemical and thermal treatment on structural characteristics and chemical composition of detonation synthesis ultradispersed diamonds (UDDs) was studied. UDDs of five different producers were compared. Special attention was paid to structural characteristics of samples (size of coherent scattering regions, aggregation), which were determined by SEM, AFM, and X-ray diffraction methods. Impurities were analyzed by methods of mass spectrometry, atomic and absorption analysis, and X-ray spectral analysis.     

High mobility holes on hydrogen-terminated diamond surface

Boron-doped diamond was grown by the chemical vapour deposition technique, of which the surface is atomically flat. We have measured cyclotron resonance of hydrogen-terminated boron-doped diamond and found that holes have very high mobility. Furthermore, we have successfully fabricated nano-structures on the surface with use of the scanning probe microscope. These properties suggest that diamond can be a candidate material for solid state quantum devices.     

化学汽相沉积金刚石生长表面氢原子覆盖率的研究

化学汽相沉积金刚石生长表面的悬挂键是其赖以成核和生长的表面活性格点。但是两个以上悬挂键聚集在一起时,局部表面能量比较高,悬挂键之间容易发生重构,形成π键或者dimer键,成为石墨结构的生长基样点。因此,金刚石的生长主要依赖于表面上的单个悬挂键集团和气相中的碳氢活性基团。石墨则主要依赖于表面上的多个悬挂键组成的集团,石墨的生长可以被表面附近活性氢原子的刻蚀作用所抑制。对表面悬挂键的微观分布状态的统计计算结果表明,(111)和(100)生长表面的氢原子覆盖率分别为0.86单层(ML)和0.80ML时,单位表面     

Possibilities of C 1s XPS and N(E) C KVV Auger spectroscopy for identification of inherent peculiarities of diamond growth

The interaction of C-atoms and CH_n-radicals with uncleaned and argon cleaned silicon substrate and with diamond surface after H-treatment have been studied in situ by XPS and Auger spectroscopy. It was found the formation of a new chemical surface state of carbon atoms in the case of carbon atoms and radicals interaction with cleaned silicon. The same chemical state was revealed on the H-treated diamond surface. Graphite-like structure of carbon atoms was observed on the surface of unlearned silicon and H-treated diamond after interaction with carbon atoms and radicals. N(E) C KVV Auger spectrum for the new chemical state of carbon atoms significantly differs from typical spectra for sp²- and sp³-bonded carbon materials. The high energy part of this spectrum was interpreted under the hypothesis of sp³-bonded carbon atoms but with shifted fermi level position.     

微喇曼和红外光谱法研究化学气相沉积金刚石多晶膜结晶质量特性

研究了化学气相沉积多晶膜的宏观性能（颜色和透光性）与微观性能（结晶质量、相纯度和氢杂质含量）之间的关系,喇曼谱与金刚石膜中氢杂质含量（红外光谱测得）的关联性.给出了根据颜色和透明度来区分样本膜质量的实验依据,颜色较深的膜的结晶质量差、相纯度低、氢杂质含量高,1 332 cm－1金刚石特征喇曼峰强度低,半峰宽大.由于多晶膜生长不均匀性、多晶以及粗糙度的影响,生长面的微喇曼光谱随采样点变化会产生较大的偏差,而光滑生长界面的喇曼光谱随采样点的变化偏差较小,因此生长界面的喇曼光谱更能反映化学气相沉积法制备金刚石膜的整体质量.     

Co元素对硬质合金基底金刚石涂层膜基界面结合强度的影响

采用基于密度泛函理论的第一性原理平面波赝势方法, 研究了硬质合金刀具基底黏结相Co元素对金刚石涂层膜基界面结合强度的影响机理. 借助Materials Studio软件建立了WC/Diamond膜基界面模型和WC-Co/Diamond膜基界面模型, 采用CASTEP仿真软件计算了WC/Diamond膜基界面模型和WC-Co/Diamond膜基界面模型的最优稳定结构. 通过仿真计算, 获得了WC/Diamond膜基界面模型和WC-Co/Diamond膜基界面模型的界面结合能、电荷密度图及Mulliken重叠布居数. 经对比分析后发现, 硬质合金基底中磁性元素Co的存在能转移金刚石涂层膜基界面处W元素及C元素的电荷, 从而使膜基界面处的原子因失电荷而相斥, 这直接导致了金刚石涂层膜基界面间距变大, 使得金刚石涂层膜基界面结合能降低.     

Photoacoustic spectroscopy of diamond powders and polycrystalline films

Photoacoustic spectroscopy is used to study optical absorption in diamond powders and polycrystalline films. The photoacoustic spectra of diamond powders with crystallite sizes in the range from ∼100 μm to 4 nm and diamond films grown by chemical vapor deposition (CVD) had a number of general characteristic features corresponding to the fundamental absorption edge for light with photon energies exceeding the width of the diamond band gap (∼5.4 eV) and to absorption in the visible and infrared by crystal-structure defects and the presence of non-diamond carbon. For samples of thin (∼10 μm) diamond films on silicon, the photoacoustic spectra revealed peculiarities associated with absorption in the silicon substrate of light transmitted by the diamond film. The shape of the spectral dependence of the amplitude of the photoacoustic signal in the ultraviolet indicates considerable scattering of light specularly reflected from the randomly distributed faces of the diamond crystallites both in the polycrystalline films and in the powders. The dependence of the shape of the photoacoustic spectra on the light modulation frequency allows one to estimate the thermal conductivity of the diamond films, which turns out to be significantly lower than the thermal conductivity of single-crystal diamond. Fiz. Tverd. Tela (St. Petersburg) 39, 1787–1791 (October 1997)     

锌添加对大尺寸金刚石生长的影响

利用温度梯度法,在6.2—6.4 GPa,1270—1400℃条件下,通过在NiMnCo-C体系中添加不同比例的锌粉成功合成出3 mm左右的大尺寸金刚石单晶.研究了锌添加对金刚石颜色、形貌、内部氮杂质以及晶体结晶度的影响.结果表明:随着锌添加量逐渐增加,晶体的颜色逐渐变浅,晶体的透光性增强;当锌添加比例达到3 wt.%时,晶体表面出现大量不规则的凹坑;晶体内氮杂质主要以C心形式存在,随着锌添加量的增多晶体内氮含量逐渐降低,基于锌的除氮能力总结出两种可能的除氮机制;拉曼光谱测试结果表明,在锌添加量小于3.0 wt.%的研究范围内,锌的添加有利于提高晶体的结晶度.本研究不仅有助于天然金刚石形成机制的探究,而且对丰富金刚石的种类以及扩展人工合成金刚石的应用领域都有着重要意义.