Morphological instabilities in the low pressure synthesis of diamond

1992 ◽  
Vol 7 (2) ◽  
pp. 384-393 ◽  
Author(s):  
K.V. Ravi
Keyword(s):  
Growth Rates ◽  
Diamond Films ◽  
High Growth ◽  
High Growth Rate ◽  
High Rate ◽  
Diamond Growth ◽  
Diamond Crystals ◽  
Pressure Synthesis ◽  
Morphological Instabilities ◽  
The Individual

Morphological instabilities attending the high growth rate of diamond films are examined. Pertinent literature on morphological instabilities and microstructure evolution in vapor deposited films is reviewed and theoretical treatments related to the case of diamond growth are discussed. Diamond films of various thicknesses have been synthesized utilizing the combustion flame synthesis technique involving diamond growth rates of ∼1 μm/min. Films of thicknesses under 20 μm are found to be dense and the surface smoothness of such films is governed by facets on the individual crystallites that make up the film. Increasing film thicknesses, at high growth rates, results in extremely rough surfaces, the trapping of voids and discontinuities, and the incorporation of non-diamond phases in the growing film. These characteristics are typical of morphological instabilities when surface diffusion and re-evaporation processes are absent and instability is promoted by the high rate arrival of the appropriate species from the flame ambient to the surface. Factors contributing to morphological instabilities include competitive shadowing and nutrient starvation and growth anisotropy of the different crystallographic faces on individual diamond crystals. It is shown that surface temperature and the presence of oxidizing species in the flame ambient contribute to anisotropic growth of diamond crystals and hence to morphological instabilities in diamond films. An approach to avoiding these instabilities is briefly discussed.

Very High Growth Rate of 4H-SiC Using MTS as Chloride-Based Precursor

2008 ◽  
Vol 600-603 ◽  
pp. 115-118 ◽  
Author(s):  
Henrik Pedersen ◽  
Stefano Leone ◽  
Anne Henry ◽  
Franziska Christine Beyer ◽  
Vanya Darakchieva ◽  
...  
Keyword(s):  
Growth Rate ◽  
Linear Dependence ◽  
Growth Rates ◽  
Molar Fraction ◽  
High Growth ◽  
High Growth Rate ◽  
Epitaxial Layers ◽  
Single Precursor ◽  
Very High

The chlorinated precursor methyltrichlorosilane (MTS), CH3SiCl3, has been used to grow epitaxial layers of 4H-SiC in a hot wall CVD reactor, with growth rates as high as 170 µm/h at 1600°C. Since MTS contains both silicon and carbon, with the C/Si ratio 1, MTS was used both as single precursor and mixed with silane or ethylene to study the effect of the C/Si and Cl/Si ratios on growth rate and doping of the epitaxial layers. When using only MTS as precursor, the growth rate showed a linear dependence on the MTS molar fraction in the reactor up to about 100 µm/h. The growth rate dropped for C/Si < 1 but was constant for C/Si > 1. Further, the growth rate decreased with lower Cl/Si ratio.

Control of Materials and Interfaces in μc-Si:H-based Solar Cells Grown at High Rate

2011 ◽  
Vol 1321 ◽  
Author(s):  
Yasushi Sobajima ◽  
Chitose Sada ◽  
Akihisa Matsuda ◽  
Hiroaki Okamoto
Keyword(s):  
Growth Rate ◽  
Solar Cells ◽  
Film Growth ◽  
Defect Density ◽  
Density Measurement ◽  
High Growth ◽  
High Growth Rate ◽  
High Rate ◽  
Bulk Region ◽  
Dangling Bond

ABSTRACTGrowth process of microcrystalline silicon (μc-Si:H) using plasma-enhanced chemicalvapor- deposition method under high-rate-growth condition has been studied for the control of optoelectronic properties in the resulting materials. We have found two important things for the spatial-defect distribution in the resulting μc-Si:H through a precise dangling-bond-density measurement, e. g., (1) dangling-bond defects are uniformly distributed in the bulk region of μc- Si:H films independent of their crystallite size and (2) large number of dangling bonds are located at the surface of μc-Si:H especially when the film is deposited at high growth rate. Starting procedure of film growth has been investigated as an important process to control the dangling-bond-defect density in the bulk region of resulting μc-Si:H through the change in the electron temperature by the presence of particulates produced at the starting period of the plasma. Deposition of Si-compress thin layer on μc-Si:H grown at high rate followed by thermal annealing has been proposed as an effective method to reduce the defect density at the surface of resulting μc-Si:H. Utilizing the starting-procedure-controlling method and the compress-layerdeposition method together with several interface-controlling methods, we have demonstrated the fabrication of high conversion-efficiency (9.27%) substrate-type (n-i-p) μc-Si:H solar cells whose intrinsic μc-Si:H layer is deposited at high growth rate of 2.3 nm/sec.

Development of a High Rate 4H-SiC Epitaxial Growth Technique Achieving Large-Area Uniformity

2008 ◽  
Vol 600-603 ◽  
pp. 111-114 ◽  
Author(s):  
Masahiko Ito ◽  
L. Storasta ◽  
Hidekazu Tsuchida
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Free Exciton ◽  
High Growth ◽  
Maximum Growth ◽  
High Growth Rate ◽  
Maximum Growth Rate ◽  
High Rate ◽  
Intrinsic Defect ◽  
Large Area

A vertical hot-wall type epi-reactor that makes it possible to simultaneously achieve both a high rate of epitaxial growth and large-area uniformity at the same time has been developed. A maximum growth rate of 250 µm/h is achieved at 1650 °C. Thickness uniformity of 1.1 % and doping uniformity of 6.7 % for a 65 mm radius area are achieved while maintaining a high growth rate of 79 µm/h. We also succeeded in growing a 280 µm-thick epilayer with excellent surface morphology and long carrier lifetime of ~1 µs on average. The LTPL spectrum shows free exciton peaks as dominant, and few impurity-related or intrinsic defect related peaks are observed. The DLTS measurement for an epilayer grown at 80 µm/h shows low trap concentrations of 1.2×1012 cm-3 for Z1/2 center and 6.3×1011 cm-3 for EH6/7 center, respectively.

Morphology of Diamond Films Grown by DC Plasma Jet CVD

1989 ◽  
Vol 162 ◽  
Author(s):  
Kazuaki Kurihara ◽  
Ken-Ichi Sasaki ◽  
Motonobu Kawarada ◽  
Nagaaki Koshino
Keyword(s):  
Growth Rate ◽  
Microwave Plasma ◽  
Diamond Films ◽  
High Growth ◽  
Plasma Jet ◽  
High Growth Rate ◽  
Plasma Cvd ◽  
Dc Plasma ◽  
Synthesis Conditions ◽  
Microwave Plasma Cvd

ABSTRACTIt is well known that diamond films synthesized from the gas phase have well defined crystal habits which are affected strongly by synthesis conditions. Though there have been many studies of the morphologies of diamond films synthesized by microwave plasma CVD [1,2,3], there have been relatively few reports on the morphologies of these films grown using new high growth rate techniques such as DC plasma jet CVD [4]. Morphology control is very important to keep flat surface, when producing thick diamond films by high growth rate techniques. In this paper we report our investigation of the morphology and growth of diamond films synthesized by DC plasma jet CVD.

High growth rate diamond synthesis in a large area atmospheric pressure inductively coupled plasma

1990 ◽  
Vol 5 (11) ◽  
pp. 2326-2333 ◽  
Author(s):  
M. A. Cappelli ◽  
T. G. Owano ◽  
C. H. Kruger
Keyword(s):  
Growth Rates ◽  
Atmospheric Pressure ◽  
Atomic Hydrogen ◽  
Inductively Coupled Plasma ◽  
High Growth ◽  
High Growth Rate ◽  
Diamond Synthesis ◽  
Large Area ◽  
Inductively Coupled ◽  
Hydrogen Flux

A study of diamond synthesis in an atmospheric pressure inductively coupled argon-hydrogen-methane plasma is presented. The plasma generated has an active area of 20 cm2 and a free stream temperature of approximately 5000 K. Deposition experiments lasting 1 h in duration have been performed in both stagnation flow and flat plate parallel flow geometries. The diamond film deposited in both configurations are nonuniform yet fairly reproducible. The variation in the growth rates at various regions of the substrate is attributed to the variation in the surface atomic hydrogen flux. Growth rates are as high as 50 μm/h, in regions of the substrate where the atomic hydrogen flux is expected to be large. Little or no growth is observed in regions where the atomic hydrogen is expected to recombine within the thermal boundary layer before arriving at the surface. Individual particles are analyzed by micro-Raman spectroscopy. Large (50 μm) size well-faceted particles show little evidence of non-diamond carbon content and are found to be under a state of compression, displaying shifts in the principal phonon mode as great as 3 cm−1.

scholarly journals The Use of Biochar of High Growth Rate Plants to Agriculturally Remediate Heavy Metal Polluted Acidic Mine Wastes

2021 ◽  
Author(s):  
Arturo Aguirre Gómez ◽  
Laura Virginia Nuñez Balderas ◽  
Claudia Hidalgo Moreno ◽  
Jorge Dionisio Etchevers Barra
Keyword(s):  
Heavy Metal ◽  
Mine Tailings ◽  
Metal Speciation ◽  
Mine Waste ◽  
Oxygen Demand ◽  
High Growth ◽  
High Growth Rate ◽  
National Standards ◽  
High Rate ◽  
Mine Wastes

The chapter is meant to expose how a sound methodology can be instrumented to both, remediate acidic metal polluted mine wastes, taking advantage of the neutralizing power and high metal sorption affinity of biochar, and to utilize pyrolyzed material derived from high-rate growth plants (water hyacinth, Eichhornia crassipes Mart, and Eucalyptus, Eucalyptus globulus Labill), which have become of ecological relevance due to their unwanted proliferation over specific terrestrial, lacustrine or riverine environments. In addition, the proposal considers not only neutralizing the mine tailings and abating the toxic levels of specific heavy metals like Pb, Cd, Cu, Zn, etc., to fulfill the international and national standards and norms, but to conveniently combine biochar with widely used soil amendments to pass widely recognized biological tests of growth using heavy metal-sensitive plants. The approach addresses firstly: a) characterizing physiochemically mine tailings and biochar, in terms of their properties (metal speciation and contents, potential acidity and neutralization potential, chemical oxygen demand, heavy metal-biochar sorption-complexing affinities, among others), and secondly; b) creating a” fertile environment” by reconditioning, agriculturally, the heavy metal-polluted acidic mine waste to allow native vegetation, or other reforesting species, to regrow on the reclaimed site, based on the bioassay tests performances.

scholarly journals The danger of high growth combined with a large non-cash working capital base: A descriptive analysis

2002 ◽  
Vol 33 (1) ◽  
pp. 41-47
Author(s):  
W. Steyn ◽  
W. D. Hamman ◽  
E. V.D.M. Smit
Keyword(s):  
Growth Rate ◽  
Cash Flow ◽  
Descriptive Analysis ◽  
High Growth ◽  
High Growth Rate ◽  
High Rate ◽  
Working Capital ◽  
Net Profit ◽  
A Company ◽  
Operating Activities

A high growth rate may not be the ultimate measure of a successful company. This article shows that growth at too high a rate, for a company with a high non-cash working capital component, may lead to financial difficulties.While the income statement of a company is based on the accrual of income and expenses, the cash flow statement is based on the receipt and payment of cash. A company experiencing high sales growth, depending on the extent of its non-cash working capital, will find that the cash flow from operating activities before the payment of dividends will not grow as quickly as the net profit after taxation. This is because the accrual part included in the net profit after taxation is also growing at a high rate. At such a growth rate, operating activities do not generate sufficient cash to sustain the day-to-day activities of the company.

Investigation into the microbiology of a high rate jet loop activated sludge reactor treating brewery wastewater

1996 ◽  
Vol 34 (5-6) ◽  
pp. 107-112 ◽  
Author(s):  
F. B. Dilek ◽  
G. K. Anderson ◽  
J. Bloor
Keyword(s):  
Activated Sludge ◽  
Klebsiella Oxytoca ◽  
High Growth ◽  
Basic Feature ◽  
High Growth Rate ◽  
High Rate ◽  
Klebsiella Pneumonia ◽  
Brewery Wastewater ◽  
Vibrio Fluvialis ◽  
Activated Sludge Reactor

The microbiology of a jet loop activated sludge reactor treating brewery wastewater has been investigated, with a venturi system combining liquid pumping with air diffusion being the basic feature of the system. The high F/M ratio, the high growth rate of the bacteria and the high levels of turbulence registered in the jet loop reactor caused the disappearance of filamentous bacteria and the production of a cloudy effluent. The population in the reactor was mainly formed by aerobic bacteria all belonging to the Pseudomonas species. Facultative anaerobes were present in small numbers, namely Klebsiella oxytoca, Klebsiella pneumonia ssp. pneumo., Vibrio fluvialis and Aeromonas hydrophila. Very high levels of respirometric activities were recorded for the mixed liquor of the reactor. The respirometric activities of individual isolates were also found to be remarkably high, especially when treating brewery wastewater. The magnitudes of their activities were a function of their relative abundance within the reactor.

THE ABRASION RESISTANCE AND ADHESION OF HFCVD BORON AND SILICON-DOPED DIAMOND FILMS ON WC–Co DRAWING DIES

2017 ◽  
Vol 24 (07) ◽  
pp. 1750090 ◽  
Author(s):  
LIANG WANG ◽  
JINFEI LIU ◽  
TANG TANG ◽  
FANGHONG SUN ◽  
NAN XIE
Keyword(s):  
Adhesive Strength ◽  
Abrasion Resistance ◽  
Copper Wire ◽  
Diamond Films ◽  
Chemical Vapor ◽  
High Growth ◽  
Diamond Powder ◽  
Wire Drawing ◽  
High Growth Rate ◽  
Drawing Dies

Diamond films have been deposited on the interior hole surface of cobalt-cemented tungsten carbide (WC–Co) drawing dies from acetone, trimethyl borate (C3H9BO3), tetraethoxysilane (C8H[Formula: see text]O4Si, TEOS) and hydrogen mixture by hot-filament chemical vapor deposition (HFCVD) method. The structures and quality of as-deposited diamond films are characterized with field-emission scanning electron microscopy (FESEM) and Raman spectroscopy. The abrasion ratio and the adhesive strength of as-deposited diamond films are evaluated by copper wire drawing tests and ultrasonic lapping tests, respectively. The results suggest that diamond films with small grain size and high growth rate can be obtained due to the mutual effects of boron and silicon impurities in the gas phases. The results of ultrasonic lapping tests show that diamond films doped with boron and/or silicon can bear the severe erosion of the large diamond powder. Diamond films peeling off within the reduction zone of the drawing dies cannot be observed after testing of 2[Formula: see text]h. The abrasion ratio of boron and silicon-added diamond films is five times that of diamond films without any addition. Adding boron and/or silicon in the diamond films is proved to be an efficient way to obtain high-adhesive-strength and high-abrasion-resistance diamond-coated drawing dies.

Versatile High Rate Plasma Deposition and Processing with very high Frequency Excitation

1997 ◽  
Vol 467 ◽  
Author(s):  
M. Heintze
Keyword(s):  
Growth Rates ◽  
High Frequency ◽  
Plasma Deposition ◽  
Excitation Frequency ◽  
High Growth ◽  
Surface Reactivity ◽  
High Rate ◽  
Plasma Diagnostic ◽  
Very High Frequency ◽  
Very High

ABSTRACTThe interest in plasma deposition using very high frequency (VHF) excitation arose after the preparation of a-Si:H at high growth rates was demonstrated. Subsequently the improved process flexibility and the control of material properties offered by the variation of the plasma excitation frequency was recognized. The preparation of amorphous and microcrystalline thin films in a VHF-plasma is described. The increased growth rates have been attributed to an enhancement of film precursor formation at VHF, to the decreased sheath thickness as well as to an enhancement of the surface reactivity by positive ions. Plasma diagnostic investigations show that the parameters mainly affected by the excitation frequency are the ion flux to the electrodes as well as the sheaths potentials and widths, rather than the plasma density.

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