Uncoupling crystal growth and nucleation in the deposition of diamond from the gas phase

Diamond deposits of well-separated particles have been obtained by the hot filament CVD technique on Si(100) wafers. Particle counting in SEM images and determination of their linear dimensions require a separate study of growth rates and of nucleation densities as a function of time, substrate temperature (500 °C–950 °C), gas phase composition (0.5–2% CH4 in H2), and total pressure (15–76 Torr). It is shown that recent models proposed for the growth process can successfully be applied if proper consideration is given to the high catalytic activity of the growing diamond surface for the heterogeneous recombination of gaseous H-atoms. This fast reaction controls the H-atom concentration at the surface and couples growth rates and nucleation densities via the gas phase.

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Diamond Growth Rates and Quality: Dependence on Gas Phase Composition

MRS Proceedings ◽

10.1557/proc-339-285 ◽

1994 ◽

Vol 339 ◽

Cited By ~ 6

Author(s):

William D. Cassidy ◽

Edward A. Evans ◽

Yaxin Wang ◽

John C. Angus ◽

Peter K. Bachmann ◽

...

Keyword(s):

Growth Rates ◽

Diamond Surface ◽

Diamond Growth ◽

Gas Composition ◽

Chemical Potentials ◽

Co Concentration ◽

The Stability ◽

Hot Filament ◽

Tie Line

ABSTRACTDiamond growth rates and quality were studied as a function of source gas composition and correlated with position on the ternary C-H-O diagram. The chemical potentials of carbon and oxygen change dramatically on either side of the H2-CO tie line, leading to large differences in the equilibrium distribution of species. These differences are reflected in the species flux reaching the diamond surface, and hence in the quality and growth rate of the diamond. In situ microbalance measurements in a hot-filament reactor show that the reaction rate is independent of the CO concentration, but decreases with increasing O2. Quality, as measured by Raman spectroscopy, increases as the C/C+O ratio in the source gases is reduced to approach the critical value of 0.5. The stability of the filaments to decarburizing and oxidation are correlated with the carbon and oxygen chemical potentials and hence to the position on the C-H-O diagram. A preliminary ternary diagram for the C-H-F system is presented.

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Diamond growth using carbon monoxide as a carbon source

Journal of Materials Research ◽

10.1557/jmr.1992.1195 ◽

1992 ◽

Vol 7 (5) ◽

pp. 1195-1203 ◽

Cited By ~ 17

Author(s):

F.M. Cerio ◽

W.A. Weimer ◽

C.E. Johnson

Keyword(s):

Carbon Source ◽

Gas Phase ◽

Growth Rates ◽

Microwave Plasma ◽

Polycrystalline Diamond ◽

Chemical Mechanism ◽

Diamond Surface ◽

Diamond Growth ◽

Lower Growth ◽

Temperature Combustion

Polycrystalline diamond films were produced in a microwave plasma assisted CVD reactor using CO as the carbon source gas. Reactor exhaust gas compositions were determined by mass spectrometry using 2–10% CO and 0–1.5% O2 in H2 feed gas mixtures. The chemistry involved in the gas phase is similar to that which occurs when diamond is grown using hydrocarbons as carbon source gases. A chemical mechanism for the oxidation of CH4 in flames appears to be applicable to this system. Addition of O2 to the reactor feed gas results in increased growth rates for low addition levels possibly due to activation of the diamond surface, while lower growth rates result at high addition levels due to oxidation of carbon from the surface and depletion of diamond growth precursors in the gas phase. The chemical reactions that take place in the plasma are similar to those that occur in flames and hot filament reactors, indicating that the plasma acts to induce reactions that are normally associated with high temperature combustion processes.

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ON DETERMINATION OF TL, IN, NA NORMAL ATOM CONCENTRATION BY RESONANCE LINES BROADENED WITH MERCURY PRESSURE

Le Journal de Physique Colloques ◽

10.1051/jphyscol:19797405 ◽

1979 ◽

Vol 40 (C7) ◽

pp. C7-839-C7-840

Author(s):

V. G. Vdovin ◽

N. A. Vdovina

Keyword(s):

Atom Concentration ◽

Normal Atom

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Aerospace series. Test methods for metallic materials. Determination of fatigue crack growth rates using corner-cracked (CC) test pieces

10.3403/30045124 ◽

2011 ◽

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Growth Rates ◽

Test Methods ◽

Metallic Materials ◽

Test Pieces ◽

Crack Growth Rates

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Effects of Synthetic Procedures and Postsynthesis Incubation pH on Size, Shape, and Antibacterial Activity of Copper (I) Oxide Nanoparticles

Journal of Chemistry ◽

10.1155/2020/9541934 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Vinh Tien Nguyen ◽

Khanh Son Trinh

Keyword(s):

Antibacterial Activity ◽

High Surface ◽

Size Variation ◽

Reaction Rates ◽

Bacterial Suspension ◽

Oxide Nanoparticles ◽

Surface Charges ◽

Fast Reaction ◽

Sem Images ◽

Etching Effect

Copper (I) oxide nanoparticles (Cu2O NP) were synthesized by reducing CuSO4 with glucose in the presence of polyvinyl alcohol as a capping agent. We used three different synthetic procedures with a fast reaction (procedure 1p), a fast-then-slow reaction (procedure 2p), and a slow-then-fast reaction (procedure 3p). The reaction rates were controlled by changing the temperature and the speed of adding reagents. The synthesized Cu2O NP were subsequently incubated for 24 h in a pH 6 solution (Cu2O NP6) or a pH 8 solution (Cu2O NP8) at 5°C. XRD and SEM images analysis revealed that the 1p procedure produced smaller NP, while the 2p procedure produced larger but more uniform NP. The 3p procedure produced the largest NP with a higher size variation. The 24-hour acidic postsynthesis incubation resulted in an etching effect, which reduced the size and size variation of Cu2O NP6. To evaluate the antibacterial activity, E. coli suspensions were mixed with the obtained Cu2O NP (32, 96, or 160 ppm) for different time intervals (1 or 24 h) and then grown on Petri dishes at 37°C for 24 h. Higher doses, smaller sizes of Cu2O NP, and longer contact times with the bacterial suspension resulted in higher inactivation efficiencies. Cu2O NP6 showed higher antibacterial effects at low doses, possibly due to the etching effect and the positive surface charge. Increasing the Cu2O doses from 32 to 96 and 160 ppm noticeably increased the antibacterial effect of the Cu2O NP8, but not significantly for Cu2O NP6. We suggested that the Cu2O NP6 suffered from agglomeration at high doses due to their high surface activity and low surface charges.

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