Impurity Diffusion in Silicon Annealed by Semi-Continuous Laser

1982 ◽  
Vol 13 ◽  
Author(s):  
Jean-Eric Bouree ◽  
Claude Leray ◽  
Michel Rodot
Keyword(s):  
Diffusion Coefficient ◽  
Single Crystals ◽  
Effective Diffusion ◽  
Boron Doping ◽  
Laser Pulses ◽  
Diffusion Time ◽  
Impurity Diffusion ◽  
Continuous Laser ◽  
Fine Grained ◽  
A Value

ABSTRACTThe diffusion of an impurity into a solid which is irradiated by laser pulses of some milliseconds duration has been analysed in terms of effective diffusion time and temperature. In the case of Fe in Si, the diffusion coefficient is found to be similar to that measured by COLLINS and CARLSON, and independent of boron doping. In the case of Al in Si, a value of 2.10–10 cm2/ at 1400°C has been found both for single crystals and for fine-grained polycrystals.

Diffusion of nonreactive and reactive solutes through fine-grained barrier materials

1984 ◽  
Vol 21 (3) ◽  
pp. 541-550 ◽  
Author(s):  
R. W. Gillham ◽  
M. J. L. Robin ◽  
D. J. Dytynyshyn ◽  
H. M. Johnston
Keyword(s):  
Diffusion Coefficient ◽  
Distribution Coefficient ◽  
Bulk Density ◽  
Molecular Diffusion ◽  
Effective Diffusion ◽  
Fickian Diffusion ◽  
Principal Mechanism ◽  
Barrier Materials ◽  
Fine Grained ◽  
Reactive Solutes

In many cases where fine-grained geologic materials are used as barriers to the migration of contaminated fluids, the principal mechanism of contaminant transport is molecular diffusion. Thus the effective molecular diffusion coefficient is the parameter of greatest importance when predicting migration rates and contaminant fluxes. Diffusion coefficients were measured for two non-reactive solutes (36Cl and 3H) and one reactive solute (85Sr) in seven mixtures of bentonite and silica sand ranging from 0 to 100% bentonite by weight. Tortuosity factors were calculated from the results of the nonreactive diffusion experiments, and retardation factors for the reactive solute from measured distribution coefficient (Kd), bulk density, and porosity values. The results showed the diffusive transport of both the reactive and nonreactive solutes to be consistent with a Fickian diffusion equation. For practical purposes, and at the low values of bulk density used in the experiments, the effective diffusion coefficient of the reactive solute could be calculated with a reasonable degree of certainty from the measured retardation factor and an estimated value of tortuosity. The results showed that because of the interaction between the distribution coefficient, bulk density, and porosity, an increase in clay content beyond about 5–10% did not result in a further reduction of the diffusion coefficient of the reactive solute. Key words: diffusion, adsorption, retardation, tortuosity, clay liners.

Oxygen diffusion in Y1Ba2Cu3O7-δ grains: An experimental study of ozone and oxygen annealing processes

1990 ◽  
Vol 5 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Yi Song ◽  
Xiao-Dong Chen ◽  
James R. Gaines ◽  
John W. Gilje
Keyword(s):  
Experimental Study ◽  
Electrical Resistivity ◽  
Diffusion Coefficient ◽  
Oxygen Content ◽  
Oxygen Diffusion ◽  
Single Phase ◽  
Diffusion Time ◽  
Oxygen Annealing ◽  
Step Process ◽  
A Value

By monitoring the electrical resistivity of single phase polycrystalline Y1Ba2Cu3O7-δ samples while changing their oxygen content in both ozone and ordinary oxygen environments, we were able to investigate the correlation between their average oxygen content and the diffusion time for oxygen inside the grains. We model the resistivity time dependence as a two-step process and find that this explains our experimental results satisfactorily. From this model we are able to estimate a value of the oxygen diffusion coefficient from our data that agrees well with other measurements. We also conclude that while ozone and ordinary oxygen may have different effects in oxidizing the surface of grains, they show no observable differences in the oxygen diffusion process in the bulk Y1Ba2Cu3O7-δ material.

scholarly journals Determination of Diffusion Coefficient of Copper in ZnO (001) Single Crystals at 1000 °C

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 131 ◽  
Author(s):  
Primavera López-Salazar ◽  
Gabriel Juárez-Díaz ◽  
Javier Martínez-Juárez ◽  
José Luna-López ◽  
Ramón Peña Sierra ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Single Crystals ◽  
Green Emission ◽  
Nitrogen Atmosphere ◽  
Structural Defects ◽  
Electrical Measurements ◽  
A Value ◽  
Secondary Ion ◽  
Diffusion Profiles

Copper from a solid source was diffused into undoped n-type bulk ZnO (001) single crystals at 1000 °C under a nitrogen atmosphere at different diffusion times. The Cu diffusion profiles were obtained by Secondary ion mass spectroscopy (SIMS), and the fitting reveals a diffusion case from a constant concentration source. A value for the diffusion coefficient of 2.42(±0.2) × 10−12 cm2∙s−1 was obtained. Electrical measurements present an increment of carrier concentration with diffusion time, but remains n-type which indicates an increase in the donor levels produced by structural defects in ZnO. Photoluminescence (PL) spectra showed an increment of green emission intensity associated with Cu incorporation.

scholarly journals COMPARATIVE ANALYSIS OF METHODS FOR DETERMINING THE EFFECTIVE CO2 DIFFUSION COEFFICIENT IN FINE-GRAINED CONCRETE OF DIFFERENT DENSITIES

2020 ◽  
Vol 10 (1) ◽  
pp. 63-70
Author(s):  
Pavel A. FEDOROV
Keyword(s):  
Diffusion Coefficient ◽  
Comparative Analysis ◽  
Effective Diffusion ◽  
Low Permeability ◽  
Test Results ◽  
Indirect Methods ◽  
Fine Grained ◽  
Co2 Diffusion ◽  
Direct And Indirect Methods ◽  
Membrane Methods

Direct and indirect methods for determining the effective diffusion coefficient of CO2 in concrete are considered. The features of the diffusion process in a capillary-porous body are described. Based on the test results of samples of fine-grained concrete with different densities, a comparative analysis of the coefficients obtained by the main methods was carried out. The criteria for comparison were the dependence of the water-cement ratio on diffusion, as well as the rate of carbonization on time. The presence of significant deviations in the low permeability concretes of the coefficients obtained by the membrane methods of 72 % and the electrical conductivity of concrete saturated with electrolyte 85 % in the low permeability concrete from the values obtained by the carbonization method was established.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

The stirring of the medium by bull spermatozoa

1963 ◽  
Vol 157 (969) ◽  
pp. 461-472 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Short Range ◽  
Short Range Order ◽  
Effective Diffusion ◽  
Sperm Head ◽  
Special Shape ◽  
Bull Semen ◽  
Sperm Density ◽  
Bull Sperm ◽  
Diffusion Coefficient Of Oxygen

1. Bull semen diluted 1/5 or 1/10 respired at the same rate whether the manometers were stationary or shaken. 2. Respirometric experiments using a manometer flask of special shape showed that bull sperm suspensions achieve this result by increasing the effective diffusion coefficient of oxygen in the suspending medium by 900%. 3. The hypothesis is put forward ( a ) that these results are caused by the existence of short-range order, as opposed to disorder, in bull sperm suspensions, even at comparatively low sperm densities (dilution 1/8 to 1/20); ( b ) that this order produces group sperm velocities greater than those of isolated spermatozoa; and ( c ) that as a result, larger volumes of the suspending medium are convected with the ordered sperm groups, causing an augmented ‘diffusion’ of oxygen. 4. This hypothesis was examined by taking photomicrographs of sperm suspensions at different dilutions and temperatures and determining from them the distributions of (i) the distance between pairs of nearest spermatozoa; (ii) the angle of inclination of a sperm head relative to that of the spermatozoon nearest to it; and (iii) the relative position of the nearest spermatozoon. 5. Comparison of the observed distributions and the corresponding random ones showed that the spermatozoa attracted each other, so that transient sperm groups were formed, in which the spermatozoa tended to swim in the same direction. A reduction in temperature or sperm density decreased the sperm order.

Diffusion of Zinc in Two-Phase Mg-Al Alloy

2007 ◽  
Vol 263 ◽  
pp. 189-194
Author(s):  
Ivo Stloukal ◽  
Jiří Čermák
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Residual Activity ◽  
Diffusion Path ◽  
Al Alloy ◽  
Serial Sectioning ◽  
Two Phase ◽  
Interphase Boundaries ◽  
The Mean

Coefficient of 65Zn heterodiffusion in Mg17Al12 intermetallic and in eutectic alloy Mg - 33.4 wt. % Al was measured in the temperature region 598 – 698 K using serial sectioning and residual activity methods. Diffusion coefficient of 65Zn in the intermetallic can be written as DI = 1.7 × 10-2 m2 s-1 exp (-155.0 kJ mol-1 / RT). At temperatures T ≥ 648 K, where the mean diffusion path was greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Def = 2.7 × 10-2 m2 s-1 exp (-155.1 kJ mol-1 / RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Db (623 K) = 1.6 × 10-12 m2 s-1 and Db (598 K) = 4.4 × 10-13 m2 s-1.

Induced polarization and pore radius — A discussion

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. D519-D526 ◽  
Author(s):  
Andreas Weller ◽  
Zeyu Zhang ◽  
Lee Slater ◽  
Sabine Kruschwitz ◽  
Matthias Halisch
Keyword(s):  
Diffusion Coefficient ◽  
Relaxation Time ◽  
Diffusion Coefficients ◽  
Pore Radius ◽  
Mercury Porosimetry ◽  
Induced Polarization ◽  
Reliable Estimate ◽  
Characteristic Relaxation Time ◽  
A Value ◽  
Apparent Diffusion

Permeability estimation from induced polarization (IP) measurements is based on a fundamental premise that the characteristic relaxation time [Formula: see text] is related to the effective hydraulic radius [Formula: see text] controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We have examined the link between a widely used single estimate of [Formula: see text] and [Formula: see text] for an extensive database of sandstone samples, in which mercury porosimetry data confirm that [Formula: see text] is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of one or two distinct representative diffusion coefficients but instead demonstrates strong evidence for six orders of magnitude of variation in an apparent diffusion coefficient that is well-correlated with [Formula: see text] and the specific surface area per unit pore volume [Formula: see text]. Two scenarios can explain our findings: (1) the length scale defined by [Formula: see text] is not equal to [Formula: see text] and is likely much longer due to the control of pore-surface roughness or (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g., silica and clays) making up the rock. In either case, the estimation of [Formula: see text] (and hence permeability) is inherently uncertain from a single characteristic IP relaxation time as considered in this study.

scholarly journals Diffusion of calcium ions in retinal rods. A theoretical calculation.

1981 ◽  
Vol 77 (4) ◽  
pp. 475-487 ◽  
Author(s):  
S McLaughlin ◽  
J Brown
Keyword(s):  
Diffusion Coefficient ◽  
Adsorption Isotherm ◽  
Calcium Ions ◽  
Outer Segment ◽  
Effective Diffusion ◽  
Langmuir Adsorption Isotherm ◽  
Diffuse Double Layer ◽  
Langmuir Adsorption ◽  
Retinal Rods ◽  
Disk Membrane

The Fick diffusion equation is combined with the Langmuir adsorption isotherm and the relevant equations from the Gouy-Chapman theory of the electrical diffuse double layer to demonstrate that the effective diffusion coefficient of calcium ions, both in the cytoplasm of the rod outer segment and within the aqueous space bounded by the disk membrane, should be reduced by a factor of 10-100 because these ions adsorb to phospholipids present in the disk membrane.

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