Influence of structural characteristics on the thermal conductivity of polycrystalline diamond films

By analyzing the signal formed by the photoacoustic effect as a function of the light modulation frequency, it is shown that this effect may be used to determine the thermal conductivity of diamond materials. The method is checked experimentally for two types of polycrystalline diamond films grown by chemical vapor deposition with the gaseous medium activated by a dc discharge and a microwave discharge. The data obtained on the thermal conductivity of the films are discussed with reference to the results of an investigation of the optical absorption, Raman light scattering, and cathodoluminescence of similar films. It is shown that the thermal conductivity of polycrystalline diamond films depends on the structural characteristics, which are determined by the deposition conditions. Fiz. Tverd. Tela (St. Petersburg) 40, 1221–1225 (July 1998)     

Growth of diamond thin film on tool materials from a gas phase

Abstract

In the present paper, diamond films have been synthesized on tungsten carbide, sintered diamond and high pressure diamond by hot filament chemical vapour deposition method from the mixture gas of methane and hydrogen, and growth features of diamond were studied.     

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)     

氮气氛下(100)织构金刚石薄膜的成核与生长研究

利用热丝化学气相沉积法研究了氮气浓度对金刚石薄膜成核和生长的影响.实验发现氮气的 加入对金刚石成核密度影响不大,但促进了已形成的金刚石核的长大.适量的氮气不仅使金 刚石生长速率得到很大的提高,而且稳定了金刚石薄膜(100)面的生长,使金刚石薄膜具有 更好的(100)织构.利用原位光发射谱对衬底附近的化学基团进行了研究.研究表明,氮气的 引入使得金刚石生长的气相化学和表面化学性质发生了很大变化.含氮基团的萃取作用提高 了金刚石表面氢原子的脱附速率,从而提高了金刚石膜的生长速率.而含氮基团的选择吸附 使金刚石 关键词： 氮气 金刚石薄膜 织构 原位光发射谱     

Copper-induced diamond formation in amorphous carbon

Diamond formation in hydrogenated amorphous-carbon films containing ultradisperse copper has been studied by measuring IR absorption at two-phonon diamond frequencies. The anomalously high two-phonon absorption observed in the experiments has permitted improving the sensitivity of the method. Mechanisms of the two-phonon absorption enhancement are discussed in terms of the theory of a medium containing nanosized copper-doped graphite fragments. It is shown that the observed enhancement of two-phonon absorption is caused by electrical induction of the local fields induced by irradiation in diamond nanocrystals acting on adjoining copper-doped graphite fragments. Fiz. Tverd. Tela (St. Petersburg) 41, 1863–1866 (October 1999)     

掺杂CVD金刚石薄膜的应力分析

在不同实验条件下，用微波等离子体化学气相沉积(MPCVD)技术在Si基体上制备了S掺杂和B-S共掺杂CVD金刚石薄膜，利用X射线衍射仪和拉曼光谱仪研究掺杂对CVD金刚石薄膜的应力影响.研究结果发现，随着S掺杂浓度的增加，薄膜中sp²杂化碳含量和缺陷增多，CVD金刚石薄膜压应力增加；小尺寸的B原子与大尺寸的S原子共掺杂时，微量B的加入改变了CVD金刚石薄膜的应力状态，共掺杂形成B-S复合体进入金刚石晶体后降低金刚石晶体的晶格畸变程度，减少S原子在晶界上偏聚数量和晶体中非金刚石结构相含量，降低由于杂质、缺陷及sp²杂化碳含量产生的晶格畸变和薄膜压应力，提高晶格完整性. 关键词： 金刚石薄膜 掺杂 应力     

Growth and structure of epitaxial diamond films grown on Si(111) single crystals

Experiments on growing single-crystal diamond films on silicon crystals with (111) surface orientation have been performed. Results attesting to the possibility of obtaining thin heteroepitaxial films are presented. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 414–418 (10 March 1997)     

Influence of boron carbide on properties of CVD-diamond thin films at various deposition pressures

Microcrystalline boron-doped diamond (BDD) films are synthesized on the silicon substrate by the hot-filament chemical vapor deposition method under the gas mixture of hydrogen and methane in the presence of boron carbide (B₄C) placed in front of filaments. The observed results of scanning electron microscopy, Raman spectroscopy and X-ray diffraction show the morphologies. Microstructures for various deposition pressures of as-grown diamond films are found to be dependent on the change of deposition pressure. These results reveal that with the increase of deposition pressure, resistivity decreases and increase in the grain size is noted in the presence of B₄C. Resistivity shows a sudden fall of about three orders of magnitude by the addition of boron in the diamond films. This is due to the crystal integrity induced by B-atoms in the structure of diamond in the presence of B₄C. These results are also significant for the conventional applications of BDD materials. The effects of deposition pressure on the overall films morphology and the doping level dependence of the diamond films have also been discussed.     

Optical spectroscopy of the surface of nanoporous diamond films

We have studied the IR absorption spectra of samples of porous ultrananocrystalline diamond (UNC diamond) obtained by selective etching of the sp ² phase in UNC diamond films. We show that the surface of porous UNC diamond is polyfunctional. We have studied the behavior of surface hydride, carbonyl, carboxyl, and hydroxyl groups as a function of annealing temperature in air and the time kept under normal conditions for UNC diamond films previously oxidized at 430°C–450°C. In the range from a few minutes to a few months, we studied the kinetics for establishment of the steady state for the functional adsorbed layer on the diamond surface under normal conditions. The observed growth in the intensity of the transmission bands due to hydride (CH _x ) and other hydrogen-containing functional groups is explained by dissociation of water molecules on the surface of the UNC diamond films.     

Effect of nanostructured AlN coatings on the oxidation-resistant properties of optical diamond films

Diamond film is an ultra-durable optical material with high thermal conductivity and good transmission in near-infrared and far-IR (8-14 μm) wavebands. CVD diamond is subjected to oxidation at temperature higher than 780 °C bared in air for 3 min, while it can be protected from oxidation for extended exposure in air at temperature up to 900 °C by a coating of aluminum nitride. Highly oriented AlN coatings were prepared for infrared windows on diamond films by reactive sputtering method and the average surface roughness (R_a) of the coatings was about 10 nm. The deposited films were characterized by X-ray diffraction (XRD) and atom force microscope (AFM). XRD confirmed the preferential orientation nature and AFM showed nanostructures. Optical properties of diamond films coated AlN thin film was investigated using infrared spectrum (IR) compared with that for as-grown diamond films.     

Difractometric Investigations into the Influence of Conditions of Diamond Film Growth on Silicon Monocrystals

The influence of the parameters of synthesis on the growth of diamond films is investigated by difractometric methods. The growth rate of diamond films increased for methane concentrations of 2 and 4% and substrate temperatures of 1073, 1173, and 1273 K when the pressure increases from 5 to 22 kPa. A maximum growth rate of 1.2 nm/s was recorded at a pressure of 21.3 kPa, a substrate temperature of 1173 K, and a methane concentration of 4%. In this case, <110> and <311> textured or <110> + <311> doubly textured diamond films grew.     

p-Type doping of diamond films with a novel organoboron source

p-Type polycrystalline diamond films were prepared by hot-filament CVD method using a liquid cyclic organic borinate ester as the doping source. The obtained films were identified as diamond films by means of SEM and Raman spectroscopy. The resistivity of the doped films can be adjusted by changing the temperature of the boron source.     

Diamond film coated on WC/Co tools by double bias-assisted hot filament CVD

WC–6%Co cutting tool inserts were coated with diamond films using a double bias-assisted hot-filament chemical vapor deposition method. Coating of the cutting tools with chemical vapor deposition diamond is taken as a three-step process in which the growth of diamond follows the pretreatment and nucleation of the substrate. The presented operating parameters allow to substantially suppress the presence of amorphous carbon and/or graphite phases in the diamond films deposited on WC/Co tools. The substrate temperature of ∼700 °C, and a low methane concentration result in a sharp diamond Raman peak centered at 1333–34 cm⁻¹ with FWHM of 6–7 cm⁻¹ as detected by micro-Raman spectroscopy. The diamond morphology is characterized by scanning electron microscopy, optical microscopy, and micro-Raman spectroscopy.     

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     

Electroless deposition of copper and fabrication of copper micropatterns on CVD diamond film surfaces

Electroless deposition of copper on as-grown and amino-modification diamond substrates was investigated. The compact and uniform copper films were successfully electrolessly deposited on as-grown and amino-modification diamond substrates after activation by Pd/Sn colloid nanoparticles. The adhesion interaction between copper films and diamond substrates was roughly estimated by the ultrasonic treatment. The results showed the higher adhesion interaction between copper films and amino-modification diamond substrates than that between the copper films and as-grown diamond substrates due to the greater attractive force between the Pd/Sn colloid nanoparticles and amino-modified diamond surface. The favorable copper micropatterns were successfully constructed on diamond film surfaces by means of the catalyst lift-off method and the copper lift-off method. Furthermore, the electrochemical behavior of copper-modified boron-doped diamond (BDD) was studied for glucose oxidation in 0.2 M sodium hydroxide solution by using cyclic voltammetry, and the result indicated that copper-modified BDD exhibited high catalytic activity to electrochemical oxidation of glucose in alkaline media.     

Effects of hydrogen and oxygen on the electrochemical corrosion and wear-corrosion behavior of diamond films deposited by hot filament chemical vapor deposition

A diamond film was deposited on silicon substrate using hot filament chemical vapor deposition (HFCVD), and H₂ and O₂ gases were added to the deposition process for comparison. This work evaluates how adding H₂ and O₂ affects the corrosion and wear-corrosion resistance characteristics of diamond films deposited on silicon substrate. The type of atomic bonding, structure, and surface morphologies of various diamond films were analyzed by Raman spectrometry, X-ray diffraction (XRD) and atomic force microscopy (AFM). Additionally, the mechanical characteristics of diamond films were studied using a precision nano-indentation test instrument. The corrosion and wear-corrosion resistance of diamond films were studied in 1 M H₂SO₄ + 1 M NaCl solution by electrochemical polarization. The experimental results show that the diamond film with added H₂ had a denser surface and a more obvious diamond phase with sp³ bonding than the as-deposited HFCVD diamond film, effectively increasing the hardness, improving the surface structure and thereby improving corrosion and wear-corrosion resistance properties. However, the diamond film with added O₂ had more sp² and fewer sp³ bonds than the as-deposited HFCVD diamond film, corresponding to reduced corrosion and wear-corrosion resistance.     

High resolution electron energy loss spectroscopy surface studies of hydrogenated detonation nano-diamond spray-deposited films

Nano-diamond films composed of 3–5 nm grains prepared by the detonation method and spray deposited onto silicon substrates were examined by high resolution electron energy loss spectroscopy (HR-EELS), Raman spectroscopy and transmission electron microscopy. The HR-EEL spectrum of the annealed and hydrogenated films displays dominant C–H losses at 360–365 meV; the diamond optical phonon and its overtones. These results suggest that the films reveal well defined hydrogenated diamond surfaces on the nanometric scale. Detailed analysis of the diamond optical phonon overtone revealed a red-shift of the basic C–C vibration by 5 meV. We attribute this shift to a phonon quantum confinement effect detected by HR-EELS spectroscopy.     

The structure of diamond nanoclusters

A model describing the structure of diamond nanoclusters produced by explosive shocks is proposed. The model is based on experimental data obtained from x-ray diffraction and small-angle x-ray scattering. This model considers the diamond nanocluster as a crystalline diamond core coated by a carbon shell having a fractal structure. The shell structure depends both on the cooling kinetics of the detonation products and on the method used to extract from them the diamond fraction. Fiz. Tverd. Tela (St. Petersburg) 41, 740–743 (April 1999)     

On compressibility of osmium metal

On the basis of the high-pressure diamond anvil cell experiments on Os metal, Cynn et al. [Phys. Rev. Lett. 88, 135701-1 (2002)] have reported that this metal has lower compressibility than diamond. In the present work we have reanalysed the experimental data of Cynn et al. We find that the bulk moduli of Os and diamond are close to each other, implying that Os metal is as incompressible as diamond, but not more so. Our first principles total energy calculations using the full potential linearised augmented plane wave method on Os and diamond also suggest the same results.     

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.