Filament Chemical Vapor Deposition Method Research Articles

Electrical properties of diamond thin films grown by chemical vapor deposition technique

Diamond thin films grown on high resistivity, 〈100〉-oriented silicon substrates by the hot filament chemical vapor deposition method have been characterized by four-point probe and Hall effect measurements. The resistivities of both as-grown and chemically etched samples were lower than expected. The Raman spectra showed dramatic changes from two broad bands (one starting at 1250 cm−1 and peaking at 1350 cm−1 and the other starting at 1500 cm−1 and peaking at 1580 cm−1) for the as-grown samples to a sharp peak centered at 1332 cm−1 with a full width at half-maximum of 10.7 cm−1 for the chemically treated sample. Hall measurements yielded carrier concentrations in the temperature range 180–300 K. From a plot of carrier concentration vs. inverse temperature, activation energies of 0.36 and 0.20 eV are obtained for the two chemically treated samples. The resistivity values at room temperature of 100 Ω cm are significantly lower than the values recently observed for other undoped samples (ϱ=103−104 Ω cm). The low resistivity values observed in this work are attributed to the disordered graphitic regions between the diamond crystalline grains.

Time-dependent evolution of the structure and chemical bonds in diamond-like carbon films generated by the hot filament chemical vapour deposition method

The chemical structure of inhomogeneous amorphous carbon films grown for different lengths of time in a hot filament chemical vapour deposition reactor from a methane-hydrogen mixture has been investigated by electron energy loss spectroscopy (EELS) and Raman spectroscopy. The changes in EELS and Raman spectral shapes allowed us to monitor the time-dependent structural evolution of the films, from an amorphous lattice with a noticeable fraction of sp 3-bonded hydrogenated carbon atoms to a prevalence of microcrystalline graphitic domains. The depth profile of hydrogen in the grown film for 120 min has been measured by the 1H( 15N, αγ) 12C nuclear reaction analysis technique. The low value of the hydrogen content (less than 4 at.%) is consistent with the structure of this carbon film which has a density of 1.9 g cm -3. By the combined use of Rutherford backscattering spectrometry and nuclear reaction analysis the mean carbon coverage thickness was found to be 22±5 nm. Secondary ion mass spectrometry measurements confirmed this conclusion.

Diamond nucleation on epitaxially grown Y-ZrO2 layers on Si(100)

Enhanced nucleation of polycrystalline diamond has been achieved on Si(100) with an epitaxial intermediate layer of yttria stabilized zirconia (Y-ZrO2). The epitaxial Y-ZrO2 layer was grown by pulsed excimer laser ablation and the diamond deposition was accomplished using the hot filament chemical vapor deposition method. The morphological, structural, and defect properties of the diamond crystallites are studied using the techniques of scanning electron microscopy, x-ray diffraction, and laser Raman spectroscopy, respectively.

Behaviour of Co binder phase during diamond deposition on WCCo substrate

The movement of the Co-rich binder phase and its interaction with growing diamond particles during deposition were investigated by repeated observations of the same site on a WC-Co substrate surface. Both etched and unetched (as-polished) specimens of WC-5Co were used for deposition. The diamond deposition was carried out using the tungsten filament chemical vapour deposition method. Raman spectra have shown that the quality of the diamond deposited on the etched substrate was better than that on the as-polished substrate. The facet size of the diamond film surface on the as-polished substrate was smaller than that on the etched specimen. These effects were caused by the atomic-scale interaction of Co atoms in the binder phase. A special feature of the diamond film on the as-polished specimen was a very rough diamond film surface. This phenomenon was observed to result from the abnormal movement of the Co-rich binder phase to the deposited diamond particle surface and the subsequent non-uniform growth of particles during deposition. The phenomenological characteristics of the Co-rich binder phase movement were also explained.

Investigation of the growth mechanism of diamond (111) facets using high resolution electron energy loss spectroscopy

Diamond (111) facets deposited at 0.2% CH4 by remote feed with hot filament chemical vapor deposition (HFCVD) method have been investigated using high resolution electron energy loss spectroscopy (HREELS). The grown diamond (111) facets are terminated by CH radicals. With the help of atomic deuterium reaction with (111) facets, it is found that (111) facets consist of (111) faces and {110} steps, and atomic deuterium first replaces the hydrogen atoms adsorbed on (111) faces. After the continuous growth of grown diamond (111) facets at 0.2% CH4 of local feed for 30 min, CH3 vibrational modes on (111) facets have been detected. It is suggested that both C2H2 and CH3/CH4 contribute to the growth of diamond (111) surface, the C2H2 species to the growth along [011̄] direction, and CH3 radicals to the formation of kernels.

Synthesis of diamond films on Hastelloy

We have developed a two-step hot filament chemical vapor deposition method to form polycrystalline films of diamond on Hastelloy substrates. The first step at a lower temperature results in the deposition of a composite layer of carbon, diamond-like carbon, and diamond, which provide nucleation sites for diamond growth in the second step at a higher temperature. To obtain a cleaner amorphous carbon-free diamond film, we introduced an intermediate hydrogen etching step. Using this procedure, we have obtained high quality polycrystalline diamond film on Hastelloy substrates, as characterized by scanning electron microscopy and Raman measurements.

Experimental and calculational study on diamond growth by an advanced hot filament chemical vapor deposition method

An advanced hot filament chemical vapor deposition (AHF-CVD), which enables independent control of CVD parameters, was performed to investigate the effect of each CVD parameter upon diamond growth. The simple configuration of this AHF-CVD system allows modeling as a one-dimensional plug flow reactor. Gas-phase chemical reactions were modeled by taking into account the temperature distribution between the filament and the substrate, to assess the role of such chemical species as hydrogen atom and methyl radical, in diamond growth. From a comparison between the experimental and calculated results, it was strongly suggested that the methyl radical is a promising diamond precursor in a system using CH4-H2 as the source gas, and that a well-crystallized diamond would be deposited under the conditions of a large proportion of hydrogen atoms with respect to the precursor.

Determination of activation energies for diamond growth by an advanced hot filament chemical vapor deposition method

The activation energies for diamond growth were determined by an advanced hot filament chemical vapor deposition (AHF-CVD) method, which accurately controls the substrate temperature independently against other CVD parameters. The activation energies, as determined from an Arrhenius plot, were 22–24 kcal/mol in the range of 740–930 °C. These values are the lowest level reported in the literature. Reported growth mechanisms were evaluated in view of the obtained activation energies.

Local Structures of Carbon Thin Films Synthesized by the Hot Filament Chemical Vapor Deposition Method X-Ray-Absorption Near-Edge Structure and Raman Spectroscopic Studies

Various carbon thin films synthesized by the hot filament chemical vapor deposition (CVD) method with various methane concentrations in hydrogen (1.0-12.5 vol.%) and temperatures of Si substrate (770-1000°C) were characterized by X-ray-absorption near-edge structure (XANES) and Raman spectroscopies as well as by scanning electron microscopy (SEM) and X-ray diffraction. Based on these results, the structural change of carbon thin films is deduced as a function of methane concentration and substrate temperature. Comparison between the Raman and XANES spectra demonstrates the usefulness of XANES spectroscopy for the characterization of carbon thin films and the complementary character between these spectroscopies.

Chemical Vapor Deposition of Diamoind Films by an Advanced Hot Filament Method.

An advanced hot filament chemical vapor deposition method was developed to make it possible to control the substrate temperature regardless of other CVD parameters (e. g. filament temperature and filament-to-substrate distance). Independent and accurate control of the substrate temperature was achieved by resistive heating of the substrate with electric current through the substrate itself and also by noncontact optical monitoring of the substrate temperature. By employing this method, the growth rates of diamond films were measured as functions of the substrate temperature and the filament-to-substrate distance.

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.