Synthesis and purification of diamond films using the microwave plasma of a CO-H2 system

A variety of diamond films were deposited using the microwave plasma of a CO-H₂ system. Qualities of the synthesized films were correlated with the gas phase atomic hydrogen concentration monitored using optical emission spectroscopy. The amorphous components contained in the synthesized films were of a polyacetylene structure, which was possibly formed by the successive polymerization of C₂H₂ in the gas phase.Excess atomic hydrogen allowed highly crystallized diamond films to be deposited at high growth rates which included only a small amount of polyacetylene components. Two possible explanations for these results were proposed: the suppression of polyacetylene formation and the production of appropriate precursor (CH₃) for diamond synthesis under the excess atomic hydrogen condition.Finally, the ratioI _H/I _Ar (whereI is the optical emission intensity) was suggested as a decisive parameter indicating the suitability of the plasma conditions for the growth of pure diamond with good crystallinity.     

Synthesis of LaCrO3 films using spray pyrolysis technique

LaCrO₃ thin films on electrolyte yttria-stabilized zirconia (YSZ) substrates were prepared by spray pyrolysis technique in the temperature range of 600–750 °C using lanthanum and chromium nitrates as precursors. Thin films obtained at 600–650 °C appear to be a mixture of cubic La(OH)CrO₄ and cubic LaCrO₄ phases, which transforms to pure cubic LaCrO₄ with the substrate temperature increasing to 700–750 °C. After being annealed at 900 °C for 2 h, all films convert to a single cubic LaCrO₃ phase. The change of Cr2p spectra in X-ray photoelectron spectroscopy (XPS) analysis shows the similar phase transformation process. Reaction processes with respect to the substrate temperature were proposed according to X-ray diffraction (XRD) and XPS analysis. The surface morphology of the films was found to depend strongly on the substrate temperature, which would be the deciding factor of the film growth mechanisms.     

Nanocrystalline diamond films deposited using a new growth regime

Abstract

Time modulated chemical vapour deposition (TMCVD), a new method for depositing nanocrystalline diamond (NCD) coatings, is reported. The key feature of the process is that it utilises modulated methane flow to promote secondary nucleation of nanoscale diamond crystallites. The growth modes of films deposited using both TMCVD and conventional hot filament CVD methods are described. Moreover, a pictorial model showing the key stages of film growth during NCD deposition using TMCVD is presented. The ability of this new process to promote secondary diamond crystallites has been demonstrated.     

Properties of pulsed laser deposited fluorinated hydroxyapatite films on titanium

Fluorinated hydroxyapatite coated titanium was investigated for application as implant coating for bone substitute materials in orthopaedics and dentistry. Pulsed laser deposition technique was used for films preparation. Fluorinated hydroxyapatite target composition, Ca₁₀(PO₄)₆F_1.37(OH)_0.63, was maintained at 2 J/cm² of laser fluence and 500-600 °C of the substrate temperature. Prepared films had a compact microstructure, composed of spherical micrometric-size aggregates. The average surface roughness resulted to be of 3 nm for the film grown at 500 °C and of 10 nm for that grown at 600 °C, showing that the temperature increase did not favour the growth of a more fine granulated surface. The films were polycrystalline with no preferential growth orientation. The films grown at 500-600 °C were about 8 μm thick and possessed a hardness of 12-13 GPa. Lower or higher substrate temperature provides the possibility to obtain coatings with different fine texture and roughness, thus tayloring them for various applications.     

用激光法合成纳米金刚石

使脉冲激光与石墨粉在空气中相互作用,并对其氧化提纯．对产物进行的显微激光拉曼光谱（Raman）与高分辨电子显微镜（HRTEM）分析表明,产物中含大量纳米金刚石颗粒,其尺寸为5nm左右,且具有较多的晶体缺陷和残余内应力．提出了石墨转变为金刚石纳米晶的机理：在脉冲激光产生的高温高压的条件下,具有石墨结构的原子团发生快速滑移切变,形成立方金刚石晶核,碳等离子体中高化学活性的碳粒子集团使金刚石晶核迅速长大,形成金刚石微晶．     

Synthesis of nanostructured SiC using the pulsed laser deposition technique

We report the new results on the direct synthesis of nanostructured silicon carbide (SiC) materials using the pulsed laser deposition technique. Scanning electron microscopy images revealed that SiC nanoholes, nanosprouts, nanowires, and nanoneedles were obtained. The crystallographic structure, chemical composition, and bond structure of the nanoscale SiC materials were investigated using X-ray diffraction, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering spectroscopy. The transverse optical mode and longitudinal optical mode in Raman spectra were found to become sharper as the substrate temperature was increased, while the material structure evolved from amorphous to crystalline.     

Enhanced nucleation and growth of diamond thin films using a nanodiamond monolayer

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

CO2 laser deposition of diamond thin films on electronic materials

Laser-induced pyrolysis has been utilized to create gas-surface chemical reactions necessary for diamond deposition on electronic materials. A 1200 W CO₂ gas laser has been used as an energy source for depositing diamond thin films from a gas mixture of CH₄ and H₂ in a chemical vapour deposition chamber. The substrate temperature was about 500°C. The laser beam energy was largely absorbed by the gases that lead to their excitation and decomposition on contact with the nearby hot substrate. Raman spectroscopy and scanning electron microscope analysis revealed high quality, fine crystalline diamond structures.     

Synthesis of monodisperse fluorinated silica nanoparticles and their superhydrophobic thin films

Monodispersive silica nanoparticles have been synthesized via the Sto?ber process and further functionalized by adding fluorinated groups using fluoroalkylsilane in an ethanolic solution. In this process, six different sizes of fluorinated silica nanoparticles of varying diameter from 40 to 300 nm are prepared and used to deposit thin films on aluminum alloy surfaces using spin coating processes. The functionalization of silica nanoparticles by fluorinated group has been confirmed by the presence C-F bonds along with Si-O-Si bonds in the thin films as analyzed by Fourier transform infrared spectroscopy (FTIR). The surface roughnesses as well as the water contact angles of the fluorinated silica nanoparticle containing thin films are found to be increased with the increase of the diameter of the synthesized fluorinated silica nanoparticles. The thin films prepared using the fluorinated silica nanoparticles having a critical size of 119 ± 12 nm provide a surface roughness of ～0.697 μm rendering the surfaces superhydrophobic with a water contact angle of 151 ± 4°. The roughness as well as the water contact angle increases on the superhydrophobic thin films with further increase in the size of the fluorinated silica nanoparticles in the films.     

Structure of diamond and diamond like carbon thin films grown by hot-filament chemical vapour deposition technique

Micro-crystalline diamond (MCD) and diamond like carbon (DLC) thin films were deposited on silicon (100) substrates by hot-filament CVD process using a mixture of CH₄ and H₂ gases at substrate temperature between 400–800°C. The microstructure of the films were studied by X-ray diffraction and scanning electron microscopy. The low temperature deposited films were found to have a mixture of amorphous and crystalline phases. At high temperatures (> 750°C) only crystalline diamond phase was obtained. Scanning electron micrographs showed faceted microcrystals of sizes up to 2μm with fairly uniform size distribution. The structure of DLC films was studied by spectroscopic ellipsometry technique. An estimate of the amount of carbon bonds existing insp ² andsp ³ form was obtained by a specially developed modelling technique. The typical values ofsp ³/sp ² ratio in our films are between 1·88–8·02. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Growth and characterization of Ni:DLC composite films using pulsed laser deposition technique

The structure and surface morphology of Ni-incorporated diamond like carbon (Ni:DLC) films have been investigated. These films were deposited on Si substrates using pulsed laser deposition (PLD) technique. A KrF Excimer laser (λ = 248 nm) was used for co-ablation from multi component Ni–graphite target. The concentration of Ni was varied by ablating the Ni part of the target with various numbers of laser pulses. The SEM and AFM analysis reveals that the surface is composed of segregates of Ni which increases with the increase in Ni content during the growth process. The structural investigations by XRD and Raman spectroscopy provided information about the orientation of the incorporated constituent and the ordering of the carbon species. Maximum height of the nano structures which were observed on the surface was ∼50 nm. The G-peak of the graphite was shifted towards higher wave number due to enhancement in SP² sites which have been increased due to the increase in the Ni concentration. A small change in the surface roughness ranging from 7.78 nm to 13.1 nm due to increased Ni concentration was also observed.     

Thermal diffusivity measurement of CVD diamond film using a step heating technique

A step heating method for the measurement of the thermal diffusivity of diamond thin film is described. The step heating method is a transient heat flow method. Transient temperature profiles are generated in a strip-shaped sample by heating one end of the sample while the other end is clamped to a heat sink. Three thermocouples are used along the heat path. The results are compared with the literature values over the temperature range from –190 to 50°C.     

Synthesis of diamond films by pulsed liquid injection chemical vapor deposition using a mixture of acetone and water as precursor

A chemical vapor deposition reactor based on the flash evaporation of an organic liquid precursor was used to grow diamond films on Si substrates. An effective pulsed liquid injection mechanism consisting of an injector, normally used for fuel injection in internal combustion engines, injects micro-doses of the precursor to the evaporation zone at 280 °C and is instantly evaporated. The resulting vapor mixture is transported by a carrier gas to the high-temperature reaction chamber where the diamond nucleates and grows on the substrate surface at temperatures ranging from 750 to 850 °C. The injection frequency, opening time, number of pulses and other injector parameters are controlled by a computer-driven system. The diamond film morphology and structure were characterized by scanning electron microscopy and Raman spectroscopy. The as-deposited diamond films show a ball-shaped morphology with a grain size that varies from 100 to 400 nm, as well as the characteristic diamond Raman band at 1332 cm^− 1. The effects of the experimental parameters and operation principle on the diamond films quality are analyzed and discussed in terms of crystallinity, composition, structure, and morphology.     

Studies of diamond films/crystals synthesized by oxyacetylene combustion flame technique

High-quality diamond films/crystals were synthesized using the oxyacetylene combustion flame technique at atmospheric pressure in a narrow acetylene-rich region. Three nozzle configurations, single-, tilted- and multi-nozzle, were used to explore possible ways to improve the uniformity of diamond films and to increase the deposition areas. It was found from the systematic investigation that the surface morphology and crystal structure of diamond films are strongly dependent on the processing parameters such as the gas mixture ratio, r, of acetylene to oxygen, substrate temperature, and nozzle configurations. The appearance of two-dimensional spiral steps on (1 1 0) diamond surfaces was observed, which have not previously been reported in the literature. This phenomenon is explained using the concept of surface reconstruction. The observed layered steps on (1 0 0), (1 1 0), and (1 1 1) diamond planes strongly suggest that under certain conditions the synthetic diamond crystals could grow with a layer mechanism on any major plane, at least in the case of films made using combustion flames. Experimental results from X-ray diffraction and Raman spectroscopy show the presence of compressive stress along the 1 0 0 direction in the diamond films. The films also have good optical transparency, indicating potential for optical coating applications. The hardness, growth rate, film uniformity, and deposition areas of diamond films are discussed. Advantages and limitations of these three flame-torch deposition techniques are also presented.     

Synthesis of carbon films containing diamond particles by electrolysis of methanol

Carbon films containing diamond particles were deposited onto a Si (100) substrate by electrolysis of methanol under a direct current potential of 1200 V, with a current density of about 52 mA/cm², at atmospheric pressure and in the temperature range of 50-55 °C. The surface morphology, microstructure and crystalline structure of the deposited films were characterized by scanning electron microscopy (SEM), Fourier transformation infrared (FTIR) spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM) respectively. The SEM images show that the films are formed by particle clusters and a surrounding glassy phase. The Raman spectra of the films indicate that the particle clusters are composed of diamond and that the glassy phase is composed of amorphous carbon. The FTIR measurements suggest the existence of hydrogen which is mainly bonded to the sp³ carbon in the films. The transmission electron diffraction patterns further indicate that the particles in the films consist of single-crystalline diamond. Both TEM and Raman measurements have confirmed unambiguously the formation of diamond crystals in the deposit, although the particles are not uniformly distributed on the entire surface.     

Wavelength-multiplexed phase-locked laser diode interferometer using a phase-shifting technique

We propose a new signal-processing method for eliminating measurement errors that occur in the wavelength-multiplexed phase-locked laser diode interferometer. The basic idea proposed here is a very simple but effective way to improve measurement accuracy. With our scheme, the phase in the interference signal is strictly shifted by 2pi, which enables us to eliminate measurement errors. The equivalent wavelength ? is 80 mm, and the measurement accuracy reaches ~?/600. A step-height measurement was also carried out in the experiment.     

基于离子交换与激光打印技术在含氟聚酰亚胺薄膜表面制备银-铜金属线

以4,4’-六氟亚异丙基-邻苯二甲酸酐(6FDA)和4,4’-二胺基二苯醚(4,4’-ODA)为原料制备了含氟聚酰亚胺薄膜,然后通过水解、激光打印、离子交换、化学还原等技术得到银和铜双金属的图案化聚酰亚胺薄膜。通过X-射线衍射仪、四点探针测试仪、光学显微镜、扫描电子显微镜等仪器系统研究了薄膜表面金属的形成过程及水解时间与导电性的关系。实验结果表明,随着水解时间的增加,金属线条的导电性逐渐增加,电导率最大达到500s/cm。     

Growth and characterization of diamond films deposited at high-pressure using a low-power microwave plasma reactor

Diamond films were deposited on molybdenum substrates from mixtures of methane diluted in hydrogen using a high-pressure microwave plasma reactor. In this reactor, a compressed waveguide structure was used to increase the electric field strength, and accordingly the reactor was able to operate stably with low gas flow rate and microwave power. The films deposited on 12 mm diameter substrates were characterized by film morphology, Raman spectra, growth rate and crystalline quality. The morphology of diamond films deposited in this reactor depends mainly on the substrate temperature. When the deposition pressure was 48 kPa and microwave power was only 800 W, high quality diamond films could be uniformly deposited with a growth rate around 20 μm/h.