ICP etching of polycrystalline diamonds: Fabrication of diamond nano-tips for AFM cantilevers

Diamond nano-tips for measurements of living-cell activities have been fabricated from polycrystalline diamond/Si substrates using an inductively coupled plasma reactive ion etching (ICP-RIE) system. Mixtures of O₂ and CF₄ gas in a plasma was used as etching atmosphere. The etching properties of polycrystalline diamond film have been characterized. During etching of polycrystalline diamond, unintentional nano whiskers were formed due to the inhomogeneity of chemical bonds at grain boundaries. Finally, nano-tips longer than 10 μm and with an apex radius below 50 nm without nano whiskers have been realized.     

Synthesis of diamond using ultra-nanocrystalline diamonds as seeding layer and their electron field emission properties

A modified nucleation and growth process was adopted so as to improve the electron field emission (EFE) properties of diamonds films. In this process, a thin layer of ultra-nanocrystalline diamonds (UNCD), instead of bias-enhanced-nuclei, were used as nucleation layer for growing diamond films in H₂-plasma. The morphology of the grains changes profoundly due to such a modified CVD process. The geometry of the grains transform from faceted to roundish and the surface of grains changes from clear to spotty. The Raman spectroscopies and SEM micrographs imply that such a modified diamond films consist of UNCD clusters (~ 10–20 nm in size) on top of sp³-bonded diamond grains (~ 100 nm in size). Increasing the total pressure in CVD chamber deteriorated the Raman structure and hence degraded the EFE properties of the films, whereas either increasing the methane content in the H₂-based plasma or prolonged the growth time improved markedly the Raman structure and thereafter enhanced the EFE properties of diamond films. The EFE properties for the modified diamond films can be turned on at E₀ = 11.1 V/μm, achieving EFE current density as large as (J_e) = 0.7 mA/cm² at 25 V/μm applied field.     

用红外差谱表征橡胶的热老化

用傅立叶转换红外光谱（ＦＴＩＲ）研究了ＮＲ、环氧化天然橡胶（ＥＮＲ）和氯化天然橡胶（ＣＮＲ）的热老化行为。以老化前后的差减光谱表征橡胶老化过程中分子结构的动态变化,提高了灵敏度和准确性。ＮＲ与ＥＮＲ的热老化同属自动催化氧化反应,产物均为羧酸、醛、酮、醚和酯等;ＣＮＲ在８０℃时开始脱ＨＣｌ,并随老化温度的提高脱ＨＣｌ的程度增大。     

FTIR Spectra, Lattice Shrinkage, and Magnetic Properties of CoTi-Substituted M-Type Barium Hexaferrite Nanoparticles

Single-phase BaCoTiFe₁₀O₁₉ (BaCoTi-M) nanoparticles were prepared by a modified sol–gel process, using metallic chlorides as starting materials. The physical chemistry process of BaCoTi-M formation, the interdependences between composition, technological conditions, microstructure, and magnetic properties were studied by X-ray diffraction (XRD), Fourier transform-infrared (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). XRD and FTIR results show that BaCoTi-M nanoparticles formed directly from γ-Fe₂O₃, spinel ferrite, and barium salts without the formation of α-Fe₂O₃ and BaFe₂O₄. The lattice shrinkage of BaCoTi-M nanoparticles that occurred on increasing the calcining temperature from 973 to 1173 K under holding for 2 h or on increasing the holding time in the range 0–2 h at 1173 K was discovered by analyzing the dependences of lattice parameters on the heat-treatment conditions. The shrinkage led to a relatively higher concentration of magnetic Fe³⁺ cations in the unit cell, and resulted in an increase of specific saturation magnetization under the corresponding conditions. Microstructural characterization shows that the evolutions of coercivity, remnant magnetization, and squareness ratio depended on the crystal growth and the reduction of structural defect as well as a decrease of grain boundary.     

Quantitative Models for Prediction of Toxic Component Concentrations in Smoke Gases from FTIR Spectra

In this paper an overview is given of several methods for quantitative analysis of FTIR spectra. Each method has its particular advantages and disadvantages. Therefore, depending on the gas component to be analysed in smoke gas spectra, an optimal choice of method has to be made. This choice depends on several different aspects: • Is the spectral band of interest free of interfering components? • Does the absorption–concentration relation show strong deviations from Beer's law? • Are significant baseline corrections necessary? • Does the applied model need to warn for the presence of unexpected components? • Is it sufficient to use only a few wavenumbers or is a full-spectrum method necessary? It will not be easy to make the appropriate choice. However, in some cases, statistics can help, in others, a good rule of thumb is to keep the choice as simple as possible. © 1996 by John Wiley & Sons, Ltd.     

Interactions in Ternary Aqueous Solutions of NMA and Osmolytes—PARAFAC Decomposition of FTIR Spectra Series

Intermolecular interactions in aqueous solutions are crucial for virtually all processes in living cells. ATR-FTIR spectroscopy is a technique that allows changes caused by many types of such interactions to be registered; however, binary solutions are sometimes difficult to solve in these terms, while ternary solutions are even more difficult. Here, we present a method of data pretreatment that facilitates the use of the Parallel Factor Analysis (PARAFAC) decomposition of ternary solution spectra into parts that are easier to analyze. Systems of the NMA–water–osmolyte-type were used to test the method and to elucidate information on the interactions between N-Methylacetamide (NMA, a simple peptide model) with stabilizing (trimethylamine N-oxide, glycine, glycine betaine) and destabilizing osmolytes (n-butylurea and tetramethylurea). Systems that contain stabilizers change their vibrational structure to a lesser extent than those with denaturants. Changes in the latter are strong and can be related to the formation of direct NMA–destabilizer interactions.     

Growth of faceted, ballas-like and nanocrystalline diamond films deposited in CH4/H2/Ar MPCVD

The influence of Ar addition to CH₄/H₂ plasma on the crystallinity, morphology and growth rate of the diamond films deposited in MPCVD was investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. X-Ray diffraction patterns indicate that diamond films of strong (111) and weak (400) texture are produced in these samples. Faceted diamond gradually turns into ballas-like diamond with graphitic inclusions when the Ar concentration increases to above 30 vol.%, as indicated by Raman spectra. As the Ar concentration goes above 90 vol.%, nanocrystalline diamond films are formed, characterized by a 1150-cm⁻¹ peak in the Raman spectra and morphology observation. Diamond growth by CH₃ or by C₂ mechanism is proposed to interpret the change in the growth rate of diamond films with the variation of Ar content in the plasma.     

Structure and properties of Dalan detonation diamonds

This paper presents the results of an investigation of the fine crystal structure of Dalan diamonds synthesized from graphite and carbon black by detonation. The phase composition of the diamond powders was found to vary widely; the structural and structural-morphological states of diamond particles were studied. The main types and subtypes of detonation diamonds are characterized according to transmission electron microscopy data. Assumptions are made concerning diamond formation during detonation synthesis. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 108–116, January–February, 2009.     

Dynamic compaction of ultradisperse diamonds

It is established experimentally that when a powder consisting of ultradisperse diamonds is subjected loading by weak shock waves with a duration ∼10⁻⁵ sec, the mean size of the diamond particles increases by several orders of magnitude. The number of publications devoted to the shock compaction of diamond powders is not limited to those cited in this article. Besides [6, 7], we should also mention the works by D. Potter and T. Ahrens [J. Appl. Phys.,6, No. 3, 910–914 (1989)] and K. Kondo and S. Sawai [J. Am. Ceram. Soc.,73, No. 3, 1983–1991 (1990)], among others (Editor's note). All-Union Scientific Research Institute of Experimental Physics, 607200 Kremlev. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 5, pp. 136–138, September–October, 1995.     

Vibrational sum-frequency observation of synthetic diamonds

Sum-frequency generation (SFG) spectroscopy was applied to the study of plasma hydrogenated diamond C(100) surface of a synthetic diamond. Two vibrational resonance peaks with the intensities strongly dependent on the polarization combinations of the visible and infrared beams were observed at 2899 and 2924 cm⁻¹. From the results of SFG measurements for various polarization combinations, the 2899 and 2924 cm⁻¹ peaks were assigned, respectively, to the antisymmetric and symmetric CH stretching modes of HCCH group on H/C(100)-2×1 surface. In addition, a strong background signal with an oscillatory profile was observed.     

Photoelectric emission and work function of semiconducting diamonds

Photoemission of electrons was observed in p-type semiconducting diamonds. The emitted electrons responding to photons which have the necessary threshold energy are believed to have originated from filled surface states. The surface charge densities are sufficiently large so that the Fermi level is greatly affected by the surface states. The work function of the semiconducting diamonds investigated is approximately 6.0 eV.     

Raman spectroscopy studies of meteoritic diamonds

The confocal Raman micro-spectroscopy was used for extraterrestrial carbonaceous matter characterisation. Different allotropic forms of carbon, mainly graphite and lonsdaleite, were identified in various meteorites: ordinary chondrites DaG 610 and NWA 869, in NWA 3118 carbonaceous chondrite, and in iron meteorites Morasko and in Sikhote Alin.     

Crystalline structure of detonation synthesized diamonds

Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 3, pp. 126–129, May–June, 1989.     

Optical characterization of natural Argyle diamonds

Optical centers in natural diamonds from the Argyle mine have been characterized by absorption and photoluminescence techniques. Many of those diamonds show characteristic PL spectra with a large number of slowly decaying centers, most of which can be attributed to the Ni impurity. A linear correlation was observed between the intensity of the 3107 cm⁻¹ hydrogen-related peak and the concentration of IR-active nitrogen. It may be accounted for by the presence of NH₃, NH₄ and N₂ gases as sources of nitrogen during diamond growth. It is shown that the unique blue-gray color of some Argyle diamonds is determined not only by the high hydrogen content, but also a small concentration of tri-nitrogen complexes in combination with a large concentration of two- and four-nitrogen defects.     

Thermochromic and photochromic behaviour of “chameleon” diamonds

Chameleon diamonds typically change color from greyish-green to yellow when they are heated or cooled (thermochromic behaviour) or kept in the dark (photochromic behaviour). Those diamonds are type Ia with A aggregates largely dominating the nitrogen speciation. They contain moderate to high amounts of hydrogen, in addition to some isolated nitrogen and traces of nickel. Their UV Visible spectrum comprises the continuum typical of type Ib material, the 480 nm band and a broad band centred around 800 nm. It is mainly modified in the red part of the visible spectrum when the color change occurs. We here propose an electronic model consistent with all observed color behaviours, based on the premise that yellow is the stable color whereas green is the metastable one. The chameleon effect is possibly linked to a nitrogen–hydrogen complex.     

Raman and conductivity studies of boron-doped microcrystalline diamond,facetted nanocrystalline diamond and cauliflower diamond films

We present a large amount of data showing how the electrical conductivity and Raman spectra of boron-doped CVD diamond films vary as a function of both B content and film type — in particular, diamond crystallite size. Three types of film have been investigated: microcrystalline diamond (MCD), faceted nanocrystalline diamond (f-NCD) and ‘cauliflower’ diamond (c-NCD). For the same B content (measured by SIMS), the conductance of MCD films was much higher than those for the two types of smaller grained films. Multi-wavelength laser Raman spectroscopy showed that Fano interference effects were much reduced for the smaller grain-sized material. The position of the Lorentzian contribution to the 500 cm^− 1 Raman feature was used to estimate the B content in each type of film, and compared to the value measured using SIMS. We found that the Raman method overestimated the concentration of B by a factor of ~ 5 for the f-NCD and c-NCD films, although it remains reasonably accurate for MCD films. The shortfall may be explained if only a small fraction of the B found in the small-grained films is being incorporated into substitutional sites. We conclude that in diamond films with a high concentration of grain boundaries, the majority of the B (80% in some cases) must be present at sites that do not contribute to the continuum of electronic states that give rise to metallic conductivity and the Fano effects. Such sites may include (a) interstitials, (b) the surface of the crystallites, or (c) bonded within the non-diamond carbon impurities present at the grain boundaries. This suggests that heavy doping of nanograined diamond films will give rise to a material with many different conducting regions, and possibly different conducting pathways and mechanisms.     

Thermal conductivity of nanocomposites based on diamonds and nanodiamonds

The thermal conductivity of composites sintered from natural microdiamond (5–7 and 10–14 μm) and nanodiamond powders under pressure of  6.0 to 6.5 GPa at the temperature  1000 to 2000 °C for 6–20 s was measured in a steady heat flow in the temperature range of 50–200 °C. It was found that the thermal conductivity of nanodiamond composites produced in these conditions was less than 10 W/(mК) while that of natural microdiamonds was as high as 500 W/(mК).     

RVD(BRVD)金刚石的发展

2008年国际金融危机以来,欧美市场对RVD磨料级金刚石的需求量正以较快的速度回升,并导致国内RVD磨料级金刚石出口量的增加,亦进一步拉动了国内金刚石Ⅰ型料的市场行情,究其原因,与RVD(BRVD)金刚石的优异特性在国际市场上的较佳体现相关,此时的RVD人造金刚石绝非彼时的RVD人造金刚石,其差异主要表现在制造工艺,单晶品级,磨削效果,制造成本几个方面,尤其是其优良的单晶品级,高效的磨削效果,较低的制造成本,促进了它对立方氮化硼及碳化硅等超硬材料的替代性的提高,因而导致RVD人造金刖石市场需求旺盛.     

优质金黄色工业金刚石的高温高压合成

在铁基触媒中引入添加剂,利用高温高压法,成功地合成了金黄色的工业金刚石.研究发现,随着添加剂含量的提高,合成金刚石的最低压力和某确定压力下的最低生长温度都呈增加趋势.另外,这种添加剂对金刚石的自发成核有一定的抑制作用,而且随其添加量的逐渐增加,这种抑制作用逐渐增强.在光学显微镜下进行观察,发现所合成的晶体呈完整的八面体形状,包裹体少,透明度高,优晶率达到80%以上.通过与无添加剂样品合成的金刚石进行对比,发现两种情况下所合成的晶体生长速度相近,晶体形貌相似,只是前者表面的凹坑呈三角形,而后者表面的凹坑呈圆形.     

单晶金刚石在高端技术领域的应用

阐述单晶金刚石在高端技术领域的应用,包括微型超精金刚石切削工具如加工成形随意曲率超细槽的方形立铣刀,用于三维表面微凹坑和任意曲率面加工的超精纳微型球形立铣刀,以剃削和快速切削加工直线超细槽的切削工具,此外还有人造单晶金刚石制作的高压水力喷射切割装置的喷射喉管,以及单晶金刚石制作的微型光学元件,并述及大单晶CVD金刚石的潜在用途.