scholarly journals Influence of Showerhead–Sample Distance (GAP) in MOVPE Close Coupled Showerhead Reactor on GaN Growth

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3375
Author(s):  
Robert Czernecki ◽  
Karolina Moszak ◽  
Wojciech Olszewski ◽  
Ewa Grzanka ◽  
Mike Leszczynski
Keyword(s):  
Growth Rate ◽  
Growth Temperature ◽  
Research Reactor ◽  
Growth Parameters ◽  
Sample Surface ◽  
Growth Pressure ◽  
Carrier Gas ◽  
Sample Distance ◽  
Main Growth

The distance between the showerhead and the sample surface (GAP) is one of the main growth parameters of the commonly used research reactor, Close Coupled Showerhead. We examine its influence on the growth rate of GaN layers deposited under various conditions (growth temperature, carrier gas, V/III ratio and growth pressure). Regardless of other growth parameters, increasing the GAP value leads to a reduction in the growth rate.

The Shape Control of ZnO Based Nanostructures

2006 ◽  
Vol 6 (11) ◽  
pp. 3628-3632
Author(s):  
M. N. Jung ◽  
S. Y. Ha ◽  
H. S. Kim ◽  
H. J. Ko ◽  
H. Ko ◽  
...  
Keyword(s):  
Growth Temperature ◽  
Shape Control ◽  
Deep Level ◽  
Growth Parameters ◽  
Stoichiometric Composition ◽  
Growth Conditions ◽  
Second Phase ◽  
Gas Flux ◽  
Carrier Gas ◽  
Si Substrates

Tetrapod-shape ZnO nanostructures are formed on Si substrates by vapor phase transportation method. The effects of two important growth parameters, growth temperature and VI/II ratio, are investigated. The growth temperature is varied in the range from 600 °C to 900 °C to control the vapor pressure of group II-element and the formation process of nanostructures. VI/II ratio was changed by adjusting the flux of carrier gas which affects indirectly the supplying rate of group VI-element. From the scanning electron microscopy (SEM), systematic variation of shape including cluster, rod, wire and tetrapod was observed. ZnO tetrapods, formed at 800 °C under the carrier gas flux of 0.5 cc/mm2 min, show considerably uniform shape with 100 nm thick and 1 ∼ 1.5 μm long legs. Also stoichiometric composition (O/Zn ∼ 1) was observed without any second phase structures. While, the decrease of growth temperature and the increase of carrier gas flux, results in the irregular shaped nanostructures with non-stoichiometric composition. The excellent luminescence properties, strong excitonic UV emission at 3.25 eV without deep level emission, indicate that the high crystalline quality tetrapod structures can be formed at the optimized growth conditions.

Study of MBE ZnSe Growth Using Rheed Oscillations

1989 ◽  
Vol 145 ◽  
Author(s):  
Francoise S. Turco ◽  
M.C. Tamargo
Keyword(s):  
Growth Rate ◽  
Quantitative Study ◽  
Growth Parameters ◽  
Growth Conditions ◽  
High Energy ◽  
Growth Mechanisms ◽  
Mbe Growth ◽  
Wide Range ◽  
Main Growth

AbstractReflection high energy electron diffraction (RHEED) intensity oscillations are often used to investigate in situ the growth of III-V materials by molecular beam epitaxy (MBE). In this work, we have used RHEED oscillations to perform a quantitative study of the growth mechanisms of ZnSe, a II-VI semiconductor.Our experiments illustrate that the RHEED pattern of ZnSe is far less intense than that of III-V materials grown by MBE, and no specular spot is observed over a wide range of growth conditions. We have, however, been able to record up to 25 oscillations allowing a quantitative study of the growth of ZnSe by MBE. Thus we have used RHEED oscillations to make an in situ systematic study of the influence of the three main growth parameters (substrate temperature and Zn or Se impinging fluxes) on the ZnSe growth rate. We observed that the variation of the ZnSe growth rate is due to a non unity sticking coefficient of both Zn and Se species at the interface in the standard growth conditions used. Our observations can be described using a thermodynamic model and enable us to control the desired growth conditions. Our work demonstrates the utility of RHEED oscillations to understand the MBE growth mechanisms of II-VI compounds.

The Relationship between Surface Pits Density and Growth Parameters during the Epitaxial Growth of 4H-SiC

2016 ◽  
Vol 858 ◽  
pp. 229-232 ◽  
Author(s):  
Wei Yu Chen ◽  
Han Chieh Ho ◽  
Po Fei Yang ◽  
Liang Choo Hsia
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Growth Temperature ◽  
Growth Parameters ◽  
Lower Surface ◽  
Ratio Condition ◽  
Background Doping ◽  
Good Uniformity ◽  
Temperature And Growth ◽  
The Relationship

In this study, different parameters of 4H-SiC epitaxial growth were used to investigate the influence on surface pits density. It was found that the density of surface pits can be reduced significantly at lower C/Si ratio condition but doping uniformity became worse simultaneously. The background doping was higher than 2E15 cm-3 when C/Si ratio was lower than 1.0. Influences of growth temperature and growth rate are also discussed. The lower surface pits density 4H-SiC epilayer with good uniformity (s/mean below 2%) can be realized during optimal condition.

scholarly journals Age and growth of the white croaker Micropogonias furnieri (Perciformes: Sciaenidae) in a coastal area of Southeastern Brazilian Bight

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
Rosa S. Santos ◽  
Marcus R. da Costa ◽  
Francisco G. Araújo
Keyword(s):  
Growth Rate ◽  
Low Temperature ◽  
Growth Parameters ◽  
Direct Application ◽  
Age And Growth ◽  
Fish Populations ◽  
Edge Type ◽  
White Croaker ◽  
Micropogonias Furnieri ◽  
Available Information

ABSTRACT Studies on age and growth of fish populations have direct application in fisheries and contribute for policies of conservation. Our aim was update information on the Micropogonias furnieri growth parameters based on sagittae otoliths annulis readings, and we expected that the studied population from Southeast Brazil can reach more longevity than the reported in the available literature. We examined 286 individuals between August-2010 and July-2011 from Ubatuba Bay, SP. The Total Length ranged 200-480 mm. The determined growth parameters were: Males, L∞ =523.4mm, k = 0.05×year-1, t0 = -8.78 year; Females L∞ = 573.5mm, k = 0.06 × year-1, t0 = -7.49 year. The MI and % of edge type evidenced the formation of one ring per year during autumn/winter, coinciding with low temperature and low growth rate. These results differed from those reported for the Vazzoler’s Population I (summer), and we detected higher longevity (45-48 years) as compared with the recorded in the available information.

scholarly journals Growth of Listeria monocytogenes in Thawed Frozen Foods

2017 ◽  
Vol 80 (3) ◽  
pp. 447-453 ◽  
Author(s):  
Ai Kataoka ◽  
Hua Wang ◽  
Philip H. Elliott ◽  
Richard C. Whiting ◽  
Melinda M. Hayman
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Storage Temperature ◽  
Growth Parameters ◽  
Quadratic Model ◽  
Lag Phase ◽  
Frozen Foods ◽  
Phase Duration ◽  
Primary Model

ABSTRACT The growth characteristics of Listeria monocytogenes inoculated onto frozen foods (corn, green peas, crabmeat, and shrimp) and thawed by being stored at 4, 8, 12, and 20°C were investigated. The growth parameters, lag-phase duration (LPD) and exponential growth rate (EGR), were determined by using a two-phase linear growth model as a primary model and a square root model for EGR and a quadratic model for LPD as secondary models, based on the growth data. The EGR model predictions were compared with growth rates obtained from the USDA Pathogen Modeling Program, calculated with similar pH, salt percentage, and NaNO2 parameters, at all storage temperatures. The results showed that L. monocytogenes grew well in all food types, with the growth rate increasing with storage temperature. Predicted EGRs for all food types demonstrated the significance of storage temperature and similar growth rates among four food types. The predicted EGRs showed slightly slower rate compared with the values from the U.S. Department of Agriculture Pathogen Modeling Program. LPD could not be accurately predicted, possibly because there were not enough sampling points. These data established by using real food samples demonstrated that L. monocytogenes can initiate growth without a prolonged lag phase even at refrigeration temperature (4°C), and the predictive models derived from this study can be useful for developing proper handling guidelines for thawed frozen foods during production and storage.

Movement, Growth and natural mortality rate of the Red Spot King Prawn, Penaeus longistylus Kubo, from the Great Barrier Reef Lagoon

1990 ◽  
Vol 41 (3) ◽  
pp. 399 ◽  
Author(s):  
MCL Dredge
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Great Barrier Reef ◽  
Annual Variation ◽  
Growth Parameters ◽  
Natural Mortality ◽  
Barrier Reef ◽  
Fishing Mortality ◽  
Nursery Areas ◽  
Reef Lagoon

Movement, growth and natural mortality rate of the red spot king prawn, Penaeus longistylus, occurring in waters of the Great Barrier Reef off Townsville, Queensland, were investigated in a series of tagging experiments. Adult P. longistylus did not migrate after leaving nursery areas. Their growth rate was slower than that of the conspecific species P. plebejus, and significant inter-annual variation in growth parameters was observed. The natural mortality rate, assessed by sequential tagging experiments that eliminated the possibility of confounding with the rate of fishing mortality, was estimated to be 0.072 (week-1).

Evaluation of temperature effect on growth rate of Lactobacillus rhamnosus GG in milk using secondary models

2013 ◽  
Vol 67 (7) ◽  
Author(s):  
Ľubomír Valík ◽  
Alžbeta Medveďová ◽  
Michal Čižniar ◽  
Denisa Liptáková
Keyword(s):  
Growth Rate ◽  
Growth Parameters ◽  
Lactobacillus Rhamnosus ◽  
Probiotic Bacterium ◽  
Extended Model ◽  
Temperature Model ◽  
Lactobacillus Rhamnosus Gg ◽  
Model Application ◽  
Cardinal Temperature ◽  
Cardinal Temperatures

AbstractThe application of secondary temperature models on growth rates of Lactobacillus rhamnosus GG, the much studied probiotic bacterium, is investigated. Growth parameters resulting from a primary fitting were modelled against temperature using the following models: Hinshelwood model (H), Ratkowsky extended model (RTK2), Zwietering model (ZWT), and cardinal temperature model with inflection (CTMI). As experienced by other authors, the RTK2, ZWT, and CTMI models provided the best statistical indices related to fitting the experimental data. Moreover, with the biological background, the following cardinal temperatures of L. rhamnosus GG resulted from the study by the model application: t min = 2.7°C, t opt = 44.4°C, t max = 52.0°C. The growth rate of the strain under study at optimal temperature was 0.88 log10(CFU mL−1 h−1).

scholarly journals Efficacy of Experimental Mouth Rinses on Caries-Related Biofilms in vitro

2021 ◽  
Vol 2 ◽  
Author(s):  
Josiana Steiger ◽  
Olivier Braissant ◽  
Tuomas Waltimo ◽  
Monika Astasov-Frauenhoffer
Keyword(s):  
Growth Rate ◽  
Antimicrobial Agents ◽  
Growth Parameters ◽  
Screening Method ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Screening Process ◽  
Mouth Rinses ◽  
Amine Fluoride

This study assessed the efficacy of tin and Polyethylenglycol (PEG-3) tallow aminopropylamine in different concentrations on Streptococcus mutans (S. mutans) biofilms to establish a new screening process for different antimicrobial agents and to gain more information on the antibacterial effects of these agents on cariogenic biofilms. Isothermal microcalorimetry (IMC) was used to determine differences in two growth parameters: lag time and growth rate; additionally, reduction in active biofilms was calculated. Experimental mouth rinses with 400 and 800 ppm tin derived from stannous fluoride (SnF2) revealed results (43.4 and 49.9% active biofilm reduction, respectively) similar to meridol mouth rinse (400 ppm tin combined with 1,567 ppm PEG-3 tallow aminopropylamine; 55.3% active biofilm reduction) (p > 0.05), while no growth of S. mutans biofilms was detected during 72 h for samples treated with an experimental rinse containing 1,600 ppm tin (100% active biofilm reduction). Only the highest concentration (12,536 ppm) of rinses containing PEG-3 tallow aminopropylamine derived from amine fluoride (AmF) revealed comparable results to meridol (57.5% reduction in active biofilm). Lower concentrations of PEG-3 tallow aminopropylamine showed reductions of 16.9% for 3,134 ppm and 33.5% for 6,268 ppm. Maximum growth rate was significantly lower for all the samples containing SnF2 than for the samples containing control biofilms (p < 0.05); no differences were found between the control and all the PEG-3 tallow aminopropylamine (p > 0.05). The growth parameters showed high reproducibility rates within the treated groups of biofilms and for the controls; thus, the screening method provided reliable results.

scholarly journals Characterisation of III?V Multilayers Grown by Low-pressure Metal Organic Vapour-phase Epitaxy

1993 ◽  
Vol 46 (3) ◽  
pp. 435
Author(s):  
C Jagadish ◽  
A Clark ◽  
G Li ◽  
CA Larson ◽  
N Hauser ◽  
...  
Keyword(s):  
Gallium Arsenide ◽  
Growth Temperature ◽  
Deep Level ◽  
Growth Parameters ◽  
Low Pressure ◽  
Vapour Phase ◽  
Growth Conditions ◽  
Vapour Phase Epitaxy ◽  
Metal Organic ◽  
Organic Vapour

Undoped and doped layers of gallium arsenide and aluminium gallium arsenide have been grown on gallium arsenide by low-pressure metal organic vapour-phase epitaxy (MOVPE). Delta doping and growth on silicon substrates have also been attempted. Of particular interest in the present study has been the influence of growth parameters, such as growth temperature, group III mole fraction and dopant flow, on the electrical and physical properties of gallium arsenide layers. An increase in growth temperature leads to increased doping efficiency in the case of silicon, whereas the opposite is true in the case of zinc. Deep level transient spectroscopy (DTLS) studies on undoped GaAs layers showed two levels, the expected EL2 level and a carbon-related level. The determination of optimum growth conditions has allowed good quality GaAs and AlGaAs epitaxial layers to be produced for a range of applications.`

Adptatives Responses of the Species Ethmalosa fimbriata in Biétri Bay, a Highly Disturbed Environment

2021 ◽  
Vol 12 (1) ◽  
pp. 48
Author(s):  
Moussa Side ◽  
Eby Yoboué Gnamma Honorine Alla ◽  
Behiri Innocent Kakou ◽  
Béatrice Abouo Adepo-Gourene
Keyword(s):  
Growth Rate ◽  
Sexual Maturity ◽  
Reference Site ◽  
Growth Parameters ◽  
The Other ◽  
Other Hand ◽  
Males And Females ◽  
Disturbed Environment

The growth and size at first sexual maturity of the species Ethmalosa fimbriata were studied in two sites in the Ebrié lagoon: Bietri, a highly anthropized environment and Vitré 2, a reference site. Growth parameters estimated from size frequencies showed that growth in both size and weight was faster in females than in males regardless of habitat. On the other hand, specimens from Biétri bay have a slower growth rate than those from Vitré 2. In Bietri bay, individuals are characterized by early sexual maturity. They reach sexual maturity at the age of 0.55 years (about 7 months), corresponding to a size of 6.13 cm for males and 8.42 cm for females; whereas in Vitré 2, they reach sexual maturity at the age of 0.82 years (about 10 months) corresponding to a size of 10.22 cm and 12.94 cm for males and females respectively. These results show that in a highly antropic environment, the growth of Ethmalosa fimbriata is affected and individuals reproduce earlier.

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