scholarly journals Levitation and collection of diamond fine particles in the rf plasma chamber equipped with a hot filament

2011 ◽  
Vol 18 (11) ◽  
pp. 113703 ◽  
Author(s):  
S. Shimizu ◽  
T. Shimizu ◽  
W. Jacob ◽  
H. M. Thomas ◽  
G. E. Morfill
Keyword(s):  
Fine Particles ◽  
Rf Plasma ◽  
Plasma Chamber ◽  
Hot Filament ◽  
Diamond Fine

scholarly journals Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament

2012 ◽  
Vol 112 (7) ◽  
pp. 073303
Author(s):  
S. Shimizu ◽  
T. Shimizu ◽  
H. M. Thomas ◽  
G. Matern ◽  
R. W. Stark ◽  
...  
Keyword(s):  
Fine Particles ◽  
Plasma Chamber ◽  
Seed Particles ◽  
Hot Filament ◽  
Diamond Fine

synthesis of crystalline carbon nitride by chemical vapor deposition

1995 ◽  
Vol 410 ◽  
Author(s):  
Yafei Zhang ◽  
Hulin Li ◽  
Qunji Xue
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Carbon Nitride ◽  
Chemical Vapor ◽  
Raman Shift ◽  
Rf Plasma ◽  
Diffraction Spectrum ◽  
Heteroepitaxial Growth ◽  
Ni Substrate ◽  
Hot Filament

ABSTRACTCrystalline carbon nitride films have been synthesized in a rf plasma assisted hot filament chemical vapor deposition system. Large crystalline grains up to ∼10 μm in size as well as film-like regions are observed in the morphology of the films. β-C3N4 with two groups of lattice parameters ( one is consistent with the theoretical value and the other is 3% smaller) in the deposited films on polycrystalline Ni substrate has been revealed by x-ray diffraction spectrum (XRD). No Raman shift peaks have been found evidently by Raman scattering measurement, but some presently unknown diffraction peaks appeared in the XRD spectrum. It is proposed that there are possible unknown structures of crystalline C-N in the films. Heteroepitaxial growth of crystalline β-C3N4 has also been tried via a buffer layer of α-SiC on Si (100) substrate. The XRD pattern of a film show that there are only two main peaks at 2.79 Å and 1.87 Å corresponding to the (200) and (300) crystalline planes of the theoretical β-C3N4 The two main peaks indicate heteroepitaxial growth along the (100) direction of β-C3N4.

CVD diamond deposition processes investigation: CARS diagnostics/modeling

1990 ◽  
Vol 5 (11) ◽  
pp. 2387-2397 ◽  
Author(s):  
Stephen O. Hay ◽  
Ward C. Roman ◽  
Meredith B. Colket
Keyword(s):  
Total Pressure ◽  
Theoretical Calculations ◽  
Plasma Reactor ◽  
Density Fluctuations ◽  
Pressure Effects ◽  
Diamond Growth ◽  
Rf Plasma ◽  
Axial Distance ◽  
Rf Power ◽  
Hot Filament

We have applied Coherent Anti-Stokes Raman Spectroscopy (CARS), using a narrowband, scanned colinear configuration, to measure temperatures, relative concentrations, and detect species in low pressure CVD of polycrystalline diamond. CARS measurements were obtained for methane, hydrogen, and acetylene in either or both a rf plasma reactor and a hot filament reactor. In the rf PACVD experiments a mixture of 1% CH4 in H2 was used at a total pressure of 5 torr. The rf power input to the plasma was 300 watts and the H2 and CH4 flow rates were 99 and 1 seem, respectively. As acetylene (C2H2) has been proposed as an intermediate in diamond growth, it was selected for the initial series of measurements. In the absence of rf power, a sensitivity of 5 mtorr was observed; in the plasma downstream of the rf coils, no observable signal attributable to C2H2 was evident. This places an upper limit to conversion of methane to acetylene at 20%, a figure representing the observed sensitivity to C2H2. In the hot filament reactor, the gas flow was 200 sccm of 1% CH4 in H2 at a total pressure of 150 torr. Under these conditions, C2H2 was detectable. Absolute concentrations were not calculated, but the observed spectra are within an order of magnitude of our sensitivity limit. This allows estimation of the C2H2 partial pressure near the substrate as 5–50 mtorr or from 0.66 to 6.6% conversion from methane. In view of this low conversion percentage, the absence of a signal in the rf experiments must be taken as inconclusive. CARS spectra of methane were also obtained in both reactors. In the rf reactor, under similar conditions to those described previously, the methane relative concentration decreased to 25% as the rf power was increased from zero to 400 watts. In the hot filament reactor, CH4 CARS signal profiles were obtained as a function of axial distance from the hot filament, and parametrically as a function of filament temperature. Comparison of these profiles, in which the observed signal decayed monotonically as the filament was approached and increased monotonically downstream of the filament, was made with theoretical calculations. This comparison showed that the fluctuations were attributable to temperature/pressure effects and not to chemistry. To determine if the observed depletion in the rf plasma was similarly attributable, the CARS signal of hydrogen was observed as a function of axial distance downstream of the rf coil centerline and parametrically as a function of rf power. In contrast to expected behavior in the thermal hot filament reactor, little rotational excitation was observed in the plasma. Rotational temperatures were assigned to hydrogen based upon comparison with theoretically derived spectra. At 450 watts of rf power, rotational temperatures of 340 K were observed 4 to 6 cm downstream of the coil, the region where the 25% decrease in CH4 was observed. Little or no density fluctuations accrue due to these temperatures, indicating that the observed depletion in methane signal is attributable to decomposition or chemical reaction in the plasma. In summary, CARS is applicable to reactant species (CH4) axial profiling in both reactors, but can be limited by sensitivity in the detection of intermediate or product species (C2H2). In addition, CARS thermometry can be utilized to profile the rotational temperatures of selected species.

Specific Surface Area of Carbon Fine Particles Including Single-Walled Carbon Nanotubes Synthesized by Hot-Filament Plasma Assisted Chemical Vapor Deposition

2014 ◽  
Vol 1586 ◽  
Author(s):  
Ryuhei Yamada ◽  
Yasuhiro Masaki ◽  
Yasuaki Hayashi
Keyword(s):  
Carbon Nanotubes ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Vapor Deposition ◽  
Fine Particles ◽  
Chemical Vapor ◽  
Single Walled Carbon Nanotubes ◽  
Hot Filament ◽  
Walled Carbon Nanotubes

ABSTRACTCarbon fine particles including single-walled carbon nanotubes (SWNTs) were synthesized by hot-filament and plasma assisted chemical vapor deposition. Specific surface area was evaluated for carbon fine particles synthesized under optimized conditions along with purified SWNTs and multi-walled carbon nanotubes (MWNTs) for comparison. The value of specific surface area for the synthesized carbon fine particles was smaller than the SWNTs, but larger than the MWNTs. Pore size distribution was analyzed with desorption isotherms by the DH method. Although smaller pores are included in the purified SWNTs than the synthesized carbon fine particles, pores of size larger than several nm were included more in the synthesized carbon fine particles.

Diamond nucleation by carbon fibers on unscratched substrate by hot-filament chemical vapor deposition

1994 ◽  
Vol 9 (7) ◽  
pp. 1619-1621 ◽  
Author(s):  
Yoshikazu Nakamura ◽  
Kazunori Tamaki ◽  
Yoshihisa Watanabe ◽  
Shigekazu Hirayama
Keyword(s):  
Chemical Vapor Deposition ◽  
Carbon Fibers ◽  
Vapor Deposition ◽  
Fine Particles ◽  
Chemical Vapor ◽  
Nucleation Site ◽  
Cvd Method ◽  
Diamond Particles ◽  
Hot Filament Cvd ◽  
Hot Filament

In order to overcome the difficulty of nucleation of diamond particles on unscratched substrates by the chemical vapor deposition (CVD) method, carbon fibers are introduced on unscratched substrates as a nucleation site of diamond particles. With assistance of carbon fibers, diamond particles can be synthesized on unscratched silicon substrate from a gas mixture of methane and hydrogen by the hot-filament CVD method. From SEM observations, nucleation of diamond particles has been confirmed on fibers at the beginning of deposition. Fine particles have formed initially on the rugged surface of fibers, and then they grow up to be diamond particles. Detailed SEM observations reveal nucleation has occurred on irregular surfaces such as boundaries on carbon fibers. We propose that nucleation of diamond particles can be controlled by arranging carbon fibers on the substrate without applying any mechanical pretreatment.

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