A Study of the Effect of the Hydrogen Gas Flow on the Quality of Thin CVD Diamond Films Deposited on Silicon Substrates in CH4/H2 Gas Mixture

2005 ◽  
Author(s):  
Mohannad Bataineh
Keyword(s):  
Gas Flow ◽  
Diamond Films ◽  
Cvd Diamond ◽  
Hydrogen Gas ◽  
Gas Mixture ◽  
Silicon Substrates

EFFECTS OF HYDROGEN GAS FLOW RATIO ON THE QUALITY OF NANO-DIAMOND FILMS

2002 ◽  
Vol 16 (06n07) ◽  
pp. 876-880
Author(s):  
S. G. Wang ◽  
Q. Zhang ◽  
D. J. Yang ◽  
S. F. Yoon ◽  
J. Ahn ◽  
...  
Keyword(s):  
Grain Size ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Gaseous Mixture ◽  
Hydrogen Gas ◽  
Chemical Vapor Deposition Method ◽  
Flow Ratio ◽  
Gas Flow Ratio

In this paper, we studied the effects of hydrogen gas flow ratio of [H2]/[N2 + CH4 + H2] on the quality of nanometer diamond (nano-diamond) films prepared by microwave plasma enhanced chemical vapor deposition method. Nano-diamond films were deposited on the silicon substrates from a gaseous mixture of nitrogen, methane and hydrogen. The experimental results show that if only using a gaseous mixture of nitrogen and methane, although we can obtain nano-diamond films with a grain size of about 5nm, the diamond films contain much non-diamond components. With hydrogen addition, and with increasing the hydrogen gas flow ratio from 1 to 10%, the non-diamond components in the films are significantly reduced and the grain size of the films increases from 5nm to 60nm. However optical transmittance of the films increases with increasing hydrogen gas flow ratio from 1 to 7% because of an improvement of film quality, and then decreases with further increasing hydrogen gas flow ratio owing to the increase of film roughness.

Methyl versus acetylene as diamond growth species

1990 ◽  
Vol 5 (11) ◽  
pp. 2313-2319 ◽  
Author(s):  
Stephen J. Harris ◽  
L. Robbin Martin
Keyword(s):  
Diamond Film ◽  
Diamond Films ◽  
Hydrogen Gas ◽  
Diamond Growth ◽  
Silicon Substrates ◽  
Methyl Radicals ◽  
Diamond Formation ◽  
Detailed Chemistry ◽  
Concentration Diffusion

We have modeled plasma-assisted diamond growth on substrates placed in a high velocity 1-dimensional flow. The gas consisted of methane or acetylene injected into a flow of partially dissociated hydrogen gas at 800 °C. Diamond is formed only near the injector. More diamond is formed when methane is the additive, and Raman spectra show that the quality of the diamond films is also higher when methane is the additive. The model, which includes detailed chemistry, convection, concentration diffusion, and thermal diffusion, shows that with this experimental arrangement only methane and methyl radicals are present in significant quantities when methane is added, while only acetylene is present when acetylene is added. We conclude that (1) Diamond films can be grown directly from methyl radicals (or, possibly, from methane) and from acetylene. This suggests that a variety of hydrocarbons could act as growth species. (2) An environment containing methane and methyl is much more effective for growing diamond films than one containing acetylene. (3) The quality of the diamond film depends on the identity of the growth species, with acetylene producing lower quality films than methyl (or methane). (4) The fall-off in diamond formation with distance from the injector is due to destruction of species crucial to diamond growth on the silicon substrates.

Particle-Assisted Oriented Deposition of Diamond Thin Films

1996 ◽  
Vol 423 ◽  
Author(s):  
Dong-Gu Lee ◽  
Rajiv K. Singh
Keyword(s):  
Vapor Deposition ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Silicon Substrates ◽  
X Ray ◽  
Diamond Particles ◽  
Film Synthesis ◽  
Diamond Powders ◽  
Hot Filament

AbstractWe have developed a method for <111> oriented diamond film synthesis using micron-sized diamond particles. Different size of diamond powders were electrophoretically seeded on silicon substrates using diamond suspensions in organic solvents (acetone, methanol, and ethanol). Diamond suspension in acetone was found to be the best for obtaining uniform diamond seeding by electrophoresis. The thickness of diamond seeded films was changed by varying the applied voltage to observe the effect on the orientation of diamond particles. Then diamond films were deposited by the hot filament chemical vapor deposition (HFCVD) process. A preferred orientation with <111> direction normal to the substrate was obtained for monolayer coatings. The surface morphology, crystal orientation, and quality of diamond films were investigated using scanning electron microscopy, x-ray diffractometry, and Raman spectroscopy.

Improvement on the Cutting Performance of CVD Diamond Coated Drills in Drilling CFRP

2012 ◽  
Vol 499 ◽  
pp. 366-371 ◽  
Author(s):  
Jian Guo Zhang ◽  
Ben Wang ◽  
Fang Hong Sun ◽  
Hang Gao
Keyword(s):  
Thermal Conductivity ◽  
Wear Resistance ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Cutting Performance ◽  
Reinforced Plastics ◽  
Coated Tool ◽  
Hot Filament

Carbon fiber reinforced plastics (CFRP) is difficult to machine because of the extremely abrasive nature of the carbon fibers and its low thermal conductivity. CVD diamond films have many excellent properties such as wonderful wear resistance, high thermal conductivity and low friction coefficient, therefore depositing diamond films on the surface of drills is thought to be an effective way to elongate the lifetime of drills and improve the cutting performance. In this study, diamond films are deposited on the WC-Co drill using hot filament chemical vapor deposition (HFCVD) method. The results of characterization by the scanning electron microscope (SEM) and Raman spectrum indicate that the fabricated CVD diamond coated drill is covered with a layer of uniform and high-purity diamond films. The cutting performance of as-fabricated CVD diamond coated drill is evaluated in dry drilling CFRP, comparing with the uncoated WC-Co drill. The results demonstrate that the CVD diamond coated drill exhibits much stronger wear resistance. Its flank wear is about 50μm after drilling 30 holes, about one-third of that of WC-Co drill. Machining quality of the exit and internal wall of drilled holes shows better surface finish obtained by coated drill, which suggests that CVD diamond coated tool has great advantages in drilling CFRP.

Rectification and internal photoemission in metal/CVD diamond and metal/CVD diamond/silicon structures

1990 ◽  
Vol 5 (11) ◽  
pp. 2497-2501 ◽  
Author(s):  
S. A. Grot ◽  
S. Lee ◽  
G.Sh. Gildenblat ◽  
C. W. Hatfield ◽  
C. R. Wronski ◽  
...  
Keyword(s):  
Crystalline Silicon ◽  
Schottky Diodes ◽  
Diamond Films ◽  
Polycrystalline Diamond ◽  
Cvd Diamond ◽  
Silicon Substrates ◽  
Metal Contacts ◽  
Free Standing ◽  
Internal Photoemission ◽  
Silicon Structures

Schottky diodes were formed with free-standing polycrystalline thin film diamond base as well as with polycrystalline diamond films grown on crystalline silicon. Current-voltage and internal photoemission measurements were used to characterize the Schottky diodes and the diamond film. Internal photoemission measurements yielded a barrier height of 1.15 eV. A comparison of experimental data for metal contacts to free-standing diamond films and those on silicon substrates indicates that both rectification and internal photoemission originate at the metal/diamond interface.

scholarly journals Chemically vapor deposited diamond films as dosimetric material for potential clinical applications

2018 ◽  
Vol 35 (4) ◽  
pp. 702-706
Author(s):  
Renata Kabacińska ◽  
Janusz Winiecki ◽  
Krzysztof Przegiętka ◽  
Mirosław Szybowicz ◽  
Kazimierz Fabisiak ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Diamond Films ◽  
Cvd Diamond ◽  
Clinical Applications ◽  
Sample Thickness ◽  
Escape Time ◽  
Silicon Substrates ◽  
Thermally Stimulated Luminescence ◽  
Donor Acceptor ◽  
Chemically Vapor Deposited

Abstract Thermally stimulated luminescence (TL), cathodoluminescence (CL) and Raman spectroscopy of CVD diamond films grown on silicon substrates have been studied in order to obtain information on defects created during the growth, which induce the levels within the gap. TL between 300 K and 700 K, and CL from 200 nm to 1200 nm have been teasured. The glow curves show a peak located around 610 K with different intensities, depending on the sample thickness, associated with a trap of energy, equal to 0.83 eV and with attempt-to-escape-time of the order of 108 s-1. Broad CL bands observed at 428±1 nm (2.90 ±0.01 eV) and 500±1 nm (2.47±0.004 eV) are attributed to closely spaced and widely separated donor-acceptor (D-A) pairs, respectively. The TL and CL results were correlated with diamond quality estimated from Raman spectroscopy measurements.

scholarly journals SUPPRESSION OF CVD DIAMOND GROWTH ON SIDE FACE OF SUBSTRATE IN PROCESS OF GAS-PHASE PRECIPITATION

2018 ◽  
Vol 59 (8) ◽  
pp. 64
Author(s):  
Dmitry V. Teteruk ◽  
Vitaly S. Bormashov ◽  
Sergey A. Tarelkin ◽  
Nikolay V. Kornilov ◽  
Nikolay V. Luparev ◽  
...  
Keyword(s):  
Gas Phase ◽  
Diamond Films ◽  
Cvd Diamond ◽  
Diamond Growth ◽  
Structural Quality ◽  
Phase Precipitation ◽  
Diamond Layer ◽  
Side Face

CVD diamond grows on the all surfaces of the substrate, including the side faces. However, the diamond layer on side faces may be undesirable. We proposed and developed the method to suppress the CVD diamond growth on the side faces using silicon wells. The optimal geometric dimensions of the wells were determined. The studies of the structural quality of the CVD diamond films were carried out.

Measurements of gastric mucosal blood flow by hydrogen gas clearance

1984 ◽  
Vol 247 (4) ◽  
pp. G339-G345
Author(s):  
S. W. Ashley ◽  
L. Y. Cheung
Keyword(s):  
Blood Flow ◽  
Gas Flow ◽  
Mucosal Blood Flow ◽  
Gastric Mucosal Blood Flow ◽  
Close Correlation ◽  
Hydrogen Gas ◽  
Low Flow ◽  
Gas Mixture ◽  
Hydrogen Gas Clearance ◽  
Flow Rates

The validity of the use of H2 gas clearance to measure gastric mucosal blood flow (GMBF) was investigated in the intact stomach of anesthetized dogs. With a modified, more sensitive platinum electrode, we were able to reduce the H2 gas concentration to a nonflammable gas mixture. GMBF was repeatedly measured when the dogs inhaled gas containing 100, 10, and 3-5% H2. GMBF measured using 100% H2 demonstrated close correlation with inhaled gases containing 10% H2 (r = 0.84, slope = 0.89) and 3-5% H2 (r = 0.91, slope = 0.88). At a nonflammable concentration of 3% H2, it was safe to add 20% O2 into the gas mixture. The addition of O2 into the inhaled gas eliminated the transient hypoxia noted otherwise. It was also possible to reduce the gas flow rate from 5-10 to 1-3 l/min. Regression analysis of GMBF determined by inhalation of 5% H2 at these flow rates revealed a significant linear correlation (r = 0.95, slope = 1.13). In 10 dogs GMBF determined by using these low concentrations of H2 at the low flow rates also showed a good agreement (r = 0.93, slope = 0.65) with that measured by radioactive microspheres. These two methods also demonstrated comparable changes in GMBF induced by intravenous infusion of histamine and vasopressin. It was concluded that, with the technique as modified in our laboratory, H2 gas clearance could be a safe and accurate tool for quantitating gastric mucosal blood flow.

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