Mechanical, tribological, and corrosion resistant behavior of nanocrystalline diamond film deposited on M50 steel using HFCVD

Effects of CCl 4 concentration on nanocrystalline diamond film deposition in a hot-filament chemical vapor deposition reactor

Fracture and solid particle erosion of micro-crystalline, nano-crystalline and boron-doped diamond films

The effect of pressure on the deposition of nanocrystalline diamond (NCD) Films in a hot filament chemical vapor deposition (IFCVD) system was investigated using CH4/H2/Ar gas mixture. The reactor pressure was found to have the strongest influence on nucleation of nanocrystalline diamond films. The range of Ar concentration in the CH4/H2/Ar mixture that permits the deposition of nanocrystalline diamond (NCD) Film at 40 torr is 90%, while the Ar concentration needed for the transition into nanocrystalline diamond phase is 50% at 5 torr. Such pressure dependence of the nanocrystalline diamond Film growth is suggested to result from two competing effects of pressure on the concentration of reactive species near the Film growth surface, and the C2 density at lower pressure (5 torr) is higher than that at high pressure (40 torr) at the same Ar concentration.

In this work, diamond thin films were deposited using hot filament chemical vapour deposition (HFCVD) technique on Si substrate. Diamond films are typically classified into nano-crystalline diamond (NCD; grain size 500 nm) based on their grain size. Process parameters such as the ratio of methane and hydrogen concentration (%CH4/H2) and chamber pressure were varied to grow MCD and NCD films. NCD and MCD films will be used as substrate to improve the performance of MEMS resonator. Structural characteristics and quality of the MCD and NCD films were confirmed using Raman spectroscopy and the surface features were imaged using high resolution scanning electron microscopy (HRSEM).

A simple and efficient method-vacuum heat treatment gaseous boronizing was proposed to pretreat the YG6X cemented carbides for maintaining its toughness and strength of the pretreated cemented carbide, and promising for mass production. After this pretreatment, the substrate surface remained clean, and the nanocrystalline diamond (NCD) films were deposited on the pretreated cemented carbide by hot filament chemical vapor deposition (HFCVD) with methane, hydrogen and argon as reaction gases. The morphology, structure, roughness and film-substrate adhesion strength of the cemented carbide substrate and the diamond films were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), micro-Raman spectroscopy and adhesion performance test. The results show that this method of gaseous boronizing is stable and feasible. The boride layer with high temperature stability can be formed. The microhardness of the cemented carbide surface after boronizing treatment was increased by 18% compared with that of the original untreated one. The comprehensive treatment of the alkali etching followed by boronizing is more effective to improve the film-substrate adhesion performance than the two-step chemical etching pretreatment.

A dc biasing method, developed in this work, has been investigated for the control of plasma space potentials and the chemical vapor deposition of nanocrystalline diamond (NCD) films in a planar surface-wave excited plasma at gas pressures below 100mTorr. A negative dc voltage was applied to a specially shaped thin metal plate attached below the upper dielectric window with respect to the grounded substrate and discharge chamber, instead of the conventional positive substrate dc biasing method. Plasma parameters were measured using a single-probe and deposited films were evaluated by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. The application of the dc bias voltage (0to−150V) enabled the net dc bias current (−0.46–+0.6A) to be varied and plasma space potentials to be decreased over a wide range (34–7V) in the bulk region, resulting in the control of the bombarding ion energy on the grounded substrate. The vertical plasma parameter profiles showed the spatial difference in electron temperature between the local surface-wave region (∼10eV) near the upper dielectric window and the bulk region (below 3eV). It was found that the spatial difference in electron temperature permits the control of net currents and plasma space potentials in the dc biasing method. NCD films were deposited with smooth surfaces (rms=12.4nm), a deposition rate of about 63nm∕h, and a continuous surface coverage on Si substrates maintained at a temperature of about 650°C for hydrogen-based CO–H2 plasmas by biasing with −70V to the metal plate.

ABSTRACTWe report here partially stabilized zirconia (PSZ) matrix deposited with nanocrystalline diamond (NCD) films on its surface as an alternative material for pulverization disk with a potential of substituting high cost synthetic single crystal diamond. The deposition of NCD films on PSZ improved the characterization of the desorption-oxygen from PSZ matrix and enhanced the poor adhesion strength between NCD film and PSZ when N2 was used as doping gas. The results for X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed that with increasing N2 flow rate, nitrogen and desorption-oxygen were incorporated into film. The adhesion test and the pulverization test showed that enhancement in the adhesion strength as well as in the pulverization performance with increasing nitrogen and oxygen concentration in the NCD films. The results proposed to substitute a synthetic single crystal diamond with PSZ by coating nitrogen-doped NCD film.

Chemical vapor deposition (CVD) diamond coating of cemented carbide cutting tools has been an alternative to increase tool-life. Experiments have shown that residual stresses produced during films growth on cemented carbide inserts significantly increases with increasing film thickness of up to 20 μm and usually leads to film delamination. In this work alternated micro- and nanocrystalline CVD diamond films have been used to relax interface stresses and to increase diamond coatings performance. Cemented carbide inserts have been submitted to a boronizing thermal diffusion treatment prior to CVD diamond films growth. After reactive heat treatment samples were submitted to subsequently chemical etching in acid and alkaline solution. The diamond films deposition was performed using hot-filament chemical vapor deposition (HFCVD) reactor with different gas concentrations for microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films growth. As a result, we present the improvement of diamond films adherence on cemented carbide inserts, evaluated by indentation and machining tests. Samples were characterized by scanning electron microscopy and energy dispersive X ray for qualitative analysis of diamond films. X-ray diffraction was used for phases identification after boronizing process. Diamond film compressive residual stresses were analyzed by Raman scattering spectroscopy.

For many industrial applications such as biomedical instruments, optical devices and microelectromechanical systems, the control of the film structure, crystallinity and morphology is of critical importance. The crystallite size, orientation and surface roughness have a profound effect on the mechanical, optical and electrical properties of the films and therefore the final product performance. In order to reduce the crystallite size and surface roughness, inert gases were added to the methane and hydrogen mixture during chemical vapour deposition of nanocrystalline diamond films. In addition, the results on the influence of pulsed biasing on the morphology of these films are reported. Bias voltages in the range –300-0 V were investigated. Increasing the bias voltage significantly alters the crystallite size and morphology of the deposited films. Raman spectroscopy, SEM and atomic force microscopy were used to characterise the nanocrystalline diamond films. SE/501

Effect of pressure on nanocrystalline diamond films deposition by hot filament CVD technique from CH 4/H 2 gas mixture

Graphitization effects of CH 4 addition on NCD growth by first and second Raman spectra and by X-ray diffraction measurements

Nanocrystalline diamond (NCD) films are being used in a large number of applications. Also, diamond nanorods (DNRs) exhibit distinctive features that are not present in diamond films, because of the tunable large surface-to-volume ratio and tubular configuration. In this work, we report on the synthesis of DNRs by means of the bottom-up and template-free method from NCD films by the hot filament chemical vapor deposition system. The substrate materials used for diamond deposition were stainless steel (AISI 316) and chromium nitride-coated stainless steel. On both substrates, NCD films and then DNRs have been synthesized. The micro-Raman confirms that the synthesized structure is NCD. In addition, the grazing incident x-ray diffraction pattern confirms the presence of cubic diamond and rhombohedral diamond as a film on the CrN and Cr2N interlayer. Also, the DNRs are encased in an amorphous carbon (a-C) shell. The DNRs are grown on the NCD grains by a bottom-up technology and template-free method. Their orientations are almost random in the diamond thin-film surface. In addition, the density of DNRs on the NCD film for the CrN interlayer is more than for the stainless-steel substrate. The NCD/DNR films are dense, adhesive, continuous, and almost uniform on the CrN-coated stainless-steel substrate.

A newly developed nano/microcrystalline diamond composite film for thermal applications was prepared in this investigation. A microcrystalline diamond (MCD) film was deposited onto silicon substrate by hot filament chemical vapor deposition (HFCVD) method, and then a nanocrystalline diamond (NCD) film was grown onto this MCD film to obtain a NCD/MCD composite film. The root-mean-square (RMS) value of surface roughness for the composite film estimated from the atomic force microscope image was 42.7nm. Compared with 85.9nm for the MCD film. And it was also found that the thermal diffusivity increased from 32.61mm2/s to 37.63mm2/s by further growing a NCD film. Results indicated that the deposition of NCD film reduced the rough surface of the MCD film with grain sizes of the order of microns, and thus increased the efficiency of diamond films as thermal spreading device. It was found that the NCD/MCD composite film had a smoother surface and a higher thermal diffusivity compared with MCD film.

The study investigates wear performance of nanocrystalline diamond (NCD) films under reciprocating sliding conditions. The NCD films were grown by hot-filament chemical vapor deposition (HFCVD) method on (100) oriented Si wafers. The surface morphology was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and mechanical profilometry. The study focuses on the understanding of mechanisms resulting in NCD films deformation and formation of ripple patterns on the wear scars surface observed during reciprocal sliding tests. Plastic deformation of the Si wafer due to NCD film deposition and high local contact pressure and temperature during sliding lead to structural changes on the Si(100)/NCD film interface, thus causing the NCD film to deform and the characteristic ripple patterns to develop on the wear scars surface. DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7232

In a distributed antenna array reactor, microwave H2-CH4-CO2 plasmas with admixture of N2 used for the low-temperature deposition of nanocrystalline diamond (NCD) films are studied by in situ infrared laser absorption spectroscopy (LAS) and optical emission spectroscopy techniques. The experiments are carried out in order to analyze the dependence of temperatures and species densities as a function of the admixture of nitrogen. The evolution of the concentrations of the methyl radical (CH3), and of five stable molecules (NH3, HCN, CH4, C2H2, and CO), are monitored in the plasma processes by LAS using tunable lead salt diode lasers and external-cavity quantum cascade lasers (EC-QCL) as radiation sources. OES is performed simultaneously to obtain complementary information about (i) the degree of dissociation of H2 precursor gas, (ii) the gas temperature and therefore (iii) the density of atomic hydrogen, a key species in the chemistry of NCD deposition plasmas. The species temperatures are not significantly affected by the nitrogen addition. The concentrations of the various species are in the range between 1011 to 1015 molecules cm−3. HCN and CO are the major products in the plasma besides atomic hydrogen. The analysis of the nitrogen and carbon mass balances of the measured species shows that in addition to NH3 and HCN other nitrogen containing species are produced in the plasma which were not probed. It is shown that the formation of HCN consumes C atoms that can be provided from hydrocarbon species and from the deposition of carbon-containing films on the reactor walls, which results in a decrease of the measured densities of hydrocarbon species.