Cleaning during Initial Stages of Epitaxial Growth in an Ultrahigh Vacuum Rapid Thermal Chemical Vapor Deposition Reactor

1993 ◽  
Vol 334 ◽  
Author(s):  
Mahesh K. Sanganeria ◽  
Katherine E. Violette ◽  
Mehmet C. ÖZtÜRk ◽  
Gari Harris ◽  
C. Archie Lee ◽  
...  
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Oxygen Concentration ◽  
Growth Rates ◽  
Oxygen Absorption ◽  
Substrate Interface ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Si Films ◽  
Water Rinse

AbstractIn this paper, we report our results on surface preparation for the growth of epitaxial Si films. Hydrogen passivated surfaces are currently being investigated for application in Si epitaxy to eliminate the high temperature in-situ bake necessary to remove the native oxide. Hydrogen passivation is obtained by a dilute HF dip before the substrate is loaded in the process chamber. However the passivation is partially lost when the HF dip is followed by a water rinse which results in oxygen absorption on the substrate. It was found that the peak oxygen concentration at the epitaxy substrate interface increase by an order of magnitude due to a five minute water rinse. We report here that oxygen and carbon at the epitaxy substrate interface can be desorbed during initial stage of epitaxial growth by reducing epitaxial growth rate. In this work, epitaxial Si films were deposited over a wide range of growth rates obtained by varying Si2H6 flow rates. The peak oxygen concentration decreases by an order of magnitude by changing the growth rate from 3000 to 700Å/kminute for a deposition temperature of 800°C. We believe that at higher growth rates Si overgrows on absorbed oxygen maintaining epitaxial alignment reflected in the good electrical quality of the epitaxial films. However, at low growth rates oxygen has sufficient time to desorb before overgrowth can take place, improving the epitaxy substrate interface quality.

scholarly journals Growth Rate Determination through Automated TEM Image Analysis: Crystallization Studies of Doped SbTe Phase-Change Thin Films

2010 ◽  
Vol 16 (3) ◽  
pp. 291-299 ◽  
Author(s):  
Jasper L.M. Oosthoek ◽  
Bart J. Kooi ◽  
Jeff T.M. De Hosson ◽  
Rob A.M. Wolters ◽  
Dirk J. Gravesteijn ◽  
...  
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Phase Change ◽  
Growth Rates ◽  
Silicon Oxide ◽  
Random Access ◽  
Growth Front ◽  
Capping Layer ◽  
Wide Range ◽  
Order Of Magnitude

AbstractA computer-controlled procedure is outlined here that first determines the position of the amorphous-crystalline interface in an image. Subsequently, from a time series of these images, the velocity of the crystal growth front is quantified. The procedure presented here can be useful for a wide range of applications, and we apply the new approach to determine growth rates in a so-called fast-growth-type phase-change material. The growth rate (without nucleation) of this material is of interest for comparison with identical material used in phase-change random access memory cells. Crystal growth rates in the amorphous phase-change layers have been measured at various temperatures using in situ heating in a transmission electron microscope. Doped SbTe films (20 nm thick) were deposited on silicon nitride membranes, and samples with and without silicon oxide capping layer were studied. The activation energy for growth was found to be 3.0 eV. The samples without capping layer exhibit a nucleation rate that is an order of magnitude higher than the samples with a silicon oxide capping layer. This difference can be attributed to the partial oxidation of the phase-change layer in air. However, the growth rates of the samples with and without capping are quite comparable.

Combustion Instabilities Damping System Development for Dry Low NOx Emissions Operability Enhancement of a Heavy-Duty Gas Turbine

2019 ◽  
Author(s):  
Matteo Cerutti ◽  
Nicola Giannini ◽  
Bruno Schuermans ◽  
Riccardo Brenci ◽  
Alessandro Marini ◽  
...  
Keyword(s):  
Growth Rate ◽  
Gas Turbine ◽  
Growth Rates ◽  
Fine Tuning ◽  
Optimized Design ◽  
Nox Emissions ◽  
Preliminary Design ◽  
Heavy Duty ◽  
Wide Range ◽  
Heavy Duty Gas Turbine

Abstract This paper describes the development phases of a damping system for combustion instability reduction in an annular type combustor for heavy-duty gas turbine applications. As reported by the authors in a previous paper, the full scale annular test rig allowed for an extensive characterization of the combustor with realistic acoustic boundaries at engine-relevant conditions. Emissions and operability assessment over a wide range of load conditions was performed, allowing the evaluation of the response of the system near the thermo-acoustic instability onset. The instability is quantified by its acoustic growth rate. This quantity is a crucial input in the design process of dampers. A methodology has been used to extract these growth rates form measured pulsation data. Experimentally determined growth rates have been evaluated for different fuel flow rate split between the main and the pilot injections, providing input to dampers preliminary design. Given current combustor architecture constraints, a first attempt configuration has been proposed and performances evaluated in the full annular rig. Dampers have been equipped with dynamic sensors and thermocouples with the purpose of measuring the growth rate abatement and the consequent NOx emissions reduction. A dedicated numerical toolbox, in-house developed by GE Power, has been used for both dampers preliminary design and growth rate reduction evaluation. Fine tuning of dampers elements as well as design assumptions adjustments required additional experimental evaluations and design iterations. Encouraged by the successful test in the concept phase, an optimized design for engine implementation was defined, that featured a significant increased damper volume, involving combustor parts re-design. The optimized configuration was finally tested in full annular rig and results demonstrated an important enhancement of operability while maintaining NOx emissions below the target levels.

scholarly journals Development and Validation of a Predictive Model for the Growth of Vibrio vulnificus in Postharvest Shellstock Oysters

2012 ◽  
Vol 78 (6) ◽  
pp. 1675-1681 ◽  
Author(s):  
Ligia DaSilva ◽  
Salina Parveen ◽  
Angelo DePaola ◽  
John Bowers ◽  
Kathy Brohawn ◽  
...  
Keyword(s):  
Growth Rate ◽  
Chesapeake Bay ◽  
Predictive Model ◽  
Growth Rates ◽  
Vibrio Vulnificus ◽  
Assessment Model ◽  
Mobile Bay ◽  
Content Type ◽  
Wide Range ◽  
Eastern Oysters

ABSTRACTPostharvest growth ofVibrio vulnificusin oysters can increase risk of human infection. Unfortunately, limited information is available regardingV. vulnificusgrowth and survival patterns over a wide range of storage temperatures in oysters harvested from different estuaries and in different oyster species. In this study, we developed a predictive model forV. vulnificusgrowth in Eastern oysters (Crassostrea virginica) harvested from Chesapeake Bay, MD, over a temperature range of 5 to 30°C and then validated the model againstV. vulnificusgrowth rates (GRs) in Eastern and Asian oysters (Crassostrea ariakensis) harvested from Mobile Bay, AL, and Chesapeake Bay, VA, respectively. In the model development studies,V. vulnificuswas slowly inactivated at 5 and 10°C with average GRs of −0.0045 and −0.0043 log most probable number (MPN)/h, respectively. Estimated average growth rates at 15, 20, 25, and 30°C were 0.022, 0.042, 0.087, and 0.093 log MPN/h, respectively. With respect to Eastern oysters, bias (Bf) and accuracy (Af) factors for model-dependent and -independent data were 1.02 and 1.25 and 1.67 and 1.98, respectively. For Asian oysters,BfandAfwere 0.29 and 3.40. Residual variations in growth rate about the fitted model were not explained by season, region, water temperature, or salinity at harvest. Growth rate estimates for Chesapeake Bay and Mobile Bay oysters stored at 25 and 30°C showed relatively high variability and were lower than Food and Agricultural Organization (FAO)/WHOV. vulnificusquantitative risk assessment model predictions. The model provides an improved tool for designing and implementing food safety plans that minimize the risk associated withV. vulnificusin oysters.

Morphology Control, Dopant Incorporation, and Selective Epitaxial Growth of 4H-SiC at Low Temperatures Using CH3Cl Growth Precursor

2006 ◽  
Vol 911 ◽  
Author(s):  
Yaroslav Koshka ◽  
Bharat Krishnan ◽  
Huang-De Lin ◽  
Galyna Melnychuk
Keyword(s):  
Growth Rate ◽  
Low Temperature ◽  
Epitaxial Growth ◽  
Growth Surface ◽  
Epitaxial Layers ◽  
Selective Epitaxial Growth ◽  
Dopant Incorporation ◽  
Nitrogen Donor ◽  
Order Of Magnitude ◽  
Silicon Vapor

AbstractLow-temperature homoepitaxial growth of 4H-SiC using halo-carbon precursors was further investigated to address the problems limiting increase of the growth rate of the defect-free epilayers at growth temperatures below 1300°C. Enhanced etching of Si clusters in the gas phase was achieved by adding HCl during the low-temperature growth. The effective Si/C ratio above the growth surface was increased as a result of reduced depletion of silicon vapor species by cluster condensation, which resulted in drastically improved epilayer morphology and significant increase of the growth rate. An intentional insitu nitrogen doping of epitaxial layers during 1300°C growth on Si and C faces revealed more than an order of magnitude higher nitrogen donor incorporation in the C-face epitaxial layers. Finally, a feasibility of selective epitaxial growth using low-temperature masking materials such as SiO2 was demonstrated.

Effect of C/Si Ratio and Nitrogen Doping on 4H-SiC Epitaxial Growth Using Dichlorosilane Precursor

2015 ◽  
Vol 821-823 ◽  
pp. 129-132 ◽  
Author(s):  
Hai Zheng Song ◽  
M.V.S. Chandrashekhar ◽  
T.S. Sudarshan
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Nitrogen Doping ◽  
Gas Flow ◽  
Gas Flow Rate ◽  
Wide Range ◽  
N Doping ◽  
Morphological Defects ◽  
Defect Densities ◽  
Epilayer Surface

Application of dichlorosilane (DCS) in 4H-SiC epitaxial growth on 4° off-cut substrates has been studied. The effect of C/Si ratio and N2gas flow rate on epilayer properties is investigated in detail. It is found that the C/Si ratio has a significant influence on the growth rate, epilayer surface roughness (step-bunching), conversion of basal plane dislocations (BPDs), and generation of morphological defects and in-grown stacking faults. A wide range of doping concentration from p- to n+ can be controlled in DCS growth. High quality 4° off-cut SiC epilayers are achieved for C/Si=1.3 – 1.8. Addition of N2has no obvious influence on growth rate and defect densities. The BPD conversion greater than 99.8% is achieved independent of N doping without any pretreatment.

scholarly journals Global analysis of continental boundary layer new particle formation based on long-term measurements

2018 ◽  
Author(s):  
Tuomo Nieminen ◽  
Veli-Matti Kerminen ◽  
Tuukka Petäjä ◽  
Pasi P. Aalto ◽  
Mikhail Arshinov ◽  
...  
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Urban Areas ◽  
Global Analysis ◽  
Formation Rate ◽  
Particle Formation ◽  
Urban Environments ◽  
New Particle Formation ◽  
The World ◽  
Order Of Magnitude

Abstract. Atmospheric new particle formation (NPF) is an important phenomenon in terms of the global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles and growth rates in the size range of 10–25 nm using at least one year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability, taking place on about 30 % of the days in March–May and on about 10 % of the days in December–February. The median formation rate of 10 nm particles varies by about three orders of magnitude (0.01–10 cm−3 s−1) and the growth rate by about an order of magnitude (1–10 nm h−1). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate between the different measurement sites, as well as between the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in Northern America, Asia and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.

Increased Growth Rate in a SiC CVD Reactor Using HCl as a Growth Additive

2005 ◽  
Vol 483-485 ◽  
pp. 73-76 ◽  
Author(s):  
Rachael L. Myers-Ward ◽  
Olof Kordina ◽  
Z. Shishkin ◽  
Shailaja P. Rao ◽  
R. Everly ◽  
...  
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Hydrogen Chloride ◽  
Growth Rates ◽  
Growth Process ◽  
Cluster Formation ◽  
Film Morphology ◽  
Hydrogen Carrier ◽  
Low Crystalline

Hydrogen chloride (HCl) was added to a standard SiC epitaxial growth process as an additive gas. A low-pressure, hot-wall CVD reactor, using silane and propane precursors and a hydrogen carrier gas, was used for these experiments. It is proposed that the addition of HCl suppresses Si cluster formation in the gas phase, and possibly also preferentially etches material of low crystalline quality. The exact mechanism of the growth using an HCl additive is still under investigation, however, higher growth rates could be obtained and the surfaces were improved when HCl was added to the flow. The film morphology was studied using SEM and AFM and the quality with LTPL analysis, which are reported.

scholarly journals Kinetic and Surface Mechanisms to Growth of Hexagonal Boron Nitride

2002 ◽  
Vol 750 ◽  
Author(s):  
Patrícia R. R. Barreto ◽  
Alan E. Kull ◽  
Mark A. Cappelli
Keyword(s):  
Growth Rate ◽  
Boron Nitride ◽  
Gas Phase ◽  
Growth Rates ◽  
Hexagonal Boron Nitride ◽  
Great Influence ◽  
Theoretical Data ◽  
State Theory ◽  
Elementary Reactions ◽  
Wide Range

ABSTRACTA mechanism is presented for the gas-phase chemistry and surface reactions describing the growth of boron nitride films. The gas phase mechanism includes 33 species and 216 elementary reactions. Rate parameters for 117 elementary reactions were obtained from published experimental/theoretical data and those for the other 99 were determined using transition state theory. The mechanism examined here is an extension and update of a previous mechanism that contained 26 species and 67 elementary reactions. Standard reaction flux/pathway and gradient sensitivity analysis techniques are used to identify important reaction pathways. The calculations were handled through the use of the ChemKin software package. The model was applied to the growth of hexagonal boron nitride in an arcjet plasma source operating on mixture of BF3, H2 and N2. From the growth rate and experimental conditions for such reactors, this work demonstrates that species with mole fractions in the range of 1 × 10-10 − 2 × 10-4 (easily generated by gas-phase conditions) can account for the measured growth rate. A comparison of the predicted mole fractions of the gas-phase species present for the experimental residence times with those required to account for the measured film growth rates allows us to identify possible growth precursors. At the experimental settings, it is found that the residence time of the reacting species does not allow the flow to reach the chemical equilibrium, and that many radicals other than the source gases can account for the measured BN growth rate. The gas-phase is shown to be removed from thermodynamic equilibrium. For comparison, the equilibrium mole fractions were also calculated using an available equilibrium chemistry solver, STANJAN. Growth rates of 10-9 to 10-6 kg m-1 s-1 were measured for a wide range of H2, BF3 and NF3 flux. Both the finite-rate kinetics and equilibrium calculations confirm the importance of added hydrogen to facilitate boron nitride condensation from the gas phase. A simple surface mechanism with 7 steps is proposed with rate constants chosen to best fit the experimental growth kinetics. The results of the model, with surface rate coefficients determined from analogous gas-phase reactions, tuned slightly to agree with the experimental growth rates for BFx, x = 1, 2 or 3, as the rate-limiting growth precursor. It is also shown that the hydrogen atom has a great influence in the growth rate and that fluorine atom etches the hBN films.

Fiber length in young hybrid Populus stems grown at extremely different rates

1998 ◽  
Vol 28 (4) ◽  
pp. 603-608 ◽  
Author(s):  
Jeffrey D DeBell ◽  
Barbara L Gartner ◽  
Dean S DeBell
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Fiber Length ◽  
Populus Trichocarpa ◽  
Hybrid Poplar ◽  
Basal Area ◽  
Breast Height ◽  
Wide Range ◽  
Western Washington ◽  
Positive Correlations

Length of libriform fibers was measured in rings 2-7 at breast height in 7-year-old hybrid poplar stems from two clones (11-11, a Populus trichocarpa Torr. & Gray x P. deltoides Bartr. ex Marsh. hybrid; and D-01, of unknown taxonomic identity) grown in a controlled test of three spacings (0.5, 1.0, and 2.0 m) on an irrigated and fertilized site in western Washington. In each clone, samples included a very wide range of cambial growth rates, with ring widths from 1 to 19 mm. Growth rate, expressed in several ways, had no consistent effect on fiber length within rings of the same age for rings 2-6. For ring 7, however, there were positive correlations between most growth rate measures and fiber length. Whole-disk fiber length increased with overall growth rate as measured by stem diameter; this apparent anomaly is caused by the fact that fast-growing trees have more of their basal area concentrated in rings further from the pith than do slower growing trees, and these rings have longer fibers compared with rings closer to the pith.

Fatigue Crack Growth Rate Testing of Gun Steels

1986 ◽  
Vol 108 (4) ◽  
pp. 507-513 ◽  
Author(s):  
J. Morrison ◽  
C. H. Laforce
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Wide Range ◽  
Rate Testing ◽  
Growth Properties ◽  
Cyclical Loading ◽  
Crack Growth Rates

The experimental measurement of fatigue crack growth rates is an integral part of the fracture mechanics approach to safe life estimation in structures subjected to cyclical loading. To assess the variation in crack growth properties, data has been collected from five different gun steels from various sources. The experimental, analytical and statistical techniques are described, and an assessment is made of the applicability of a single growth rate expression. There are significant differences in strength, toughness and extent of autofrettage between these gun steels, and a correspondingly wide range of fatigue crack growth rates has been encountered.

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