Enhanced photoluminescence from AlGaAs/GaAs superlattice gratings fabricated by Si FIB implantation

1992 ◽  
Vol 281 ◽  
Author(s):  
A. J. Steckl ◽  
P. Chen ◽  
A. G. Choo ◽  
H. E. Jackson ◽  
J. T. Boyd ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Optical Feedback ◽  
Vacancy Concentration ◽  
Depth Profiling ◽  
Time Frame ◽  
Rapid Thermal Anneal ◽  
Enhanced Photoluminescence ◽  
Order Of Magnitude ◽  
Optical Gratings ◽  
Grating Region

ABSTRACTResults are presented on the fabrication of optical gratings on an Al0.3Ga0.7As/GaAs superlattice (SL) with equal 3.5 nm barrier and well widths, by using locally FIB-enhanced mixing. As the first step, the mechanism of the mixing was studied. Si++ was accelerated to 50 kV and lOOkV and implanted at doses ranging from 1013 to 1015/cm2. A rapid thermal anneal of 10 s at 950°C was utilized. The average Al inter-diffusion coefficient and length were calculated as a function of FIB dose from SIMS depth profiling. The mixing was significantly enhanced by the FIB implantation. The ion dose as low as l×1014/cm2 followed by RTA yields a mixing parameter of ∼90% and results in a two-order of magnitude increase in the diffusion coefficient, to a value of 4.5×10−14cm2/sec, in contrast to 1.3×10−16cm2/sec from RTA-only. The maximum mixing occurred in the region where neither Si ions nor vacancies have their maximum concentration. Instead, it coincides with the location of the positive maximum of the second derivative of the vacancy concentration profile. This fact suggests that in the time frame of RTA and with low dose, the diffusion of nonequilibrium point defects plays a major role in the process of enhancing Al-Ga interdiffusion. DBR optical gratings, consisting of thousands of spacing lines with 350nm period, were fabricated with a lOOkV FIB dose of 2×1013 andl×1014/cm2. Photoluminescence (PL) spectra were taken from the grating region as well as the unimplanted superlattice region. The PL intensity from cavity region of the DBR was about 16 times higher than that from the original SL. This PL enhancement was verified to occur in the cavity region only by spatially scanning over the entire sample. A possible mechanism for this PL enhancement is optical feedback provided by the gratings.

Vacancy Injection Enhanced Al-Ga Inter-diffusion in Si FIB Implanted Superlattice

1993 ◽  
Vol 325 ◽  
Author(s):  
P. Chen ◽  
A.J. Steckl
Keyword(s):  
Vacancy Concentration ◽  
Mixing Process ◽  
Positive Maximum ◽  
Rapid Thermal Anneal ◽  
Implantation Energy ◽  
A Value ◽  
Mixing Parameter ◽  
Order Of Magnitude ◽  
Gradient Based ◽  
Magnitude Increase

AbstractThe Al-Ga inter-diffusion induced by Si FIB implantation and subsequent RTA were investigated in an Al0.3Ga0.7As/GaAs superlattice with equal 3.5 nm barrier and well widths. Si++ was accelerated to 50 kV as well as 100kV and implanted parallel to sample normal at doses ranging from 1013 to 1015/cm2. The effect of rapid thermal anneal of 10s at 950°C was characterized by SIMS technique. In the implanted region, the inter-diffusion as well as compositional mixing were significantly enhanced. An ion dose as low as 1×1014/cm2 results in a two-order of magnitude increase in the inter-diffusion coefficient, to a value of 4.5×10-14 cm2/sec, in contrast to 1.3×10-16 cm2/sec from RTA-only. This produces a mixing parameter of σ90%. A strong depth dependence of the mixing process was observed at implantation energy of 100keV with a pinch-off region being formed at certain depth. It is noticed that the depth where this enhancement occurred is not associated with either the maximum concentration of Si ions or of vacancies. Instead, it represents the positive maximum of the second derivative of the vacancy profile, which in turn represents the vacancy injection generated by presence of a transient vacancy concentration gradient. Based on this, a theoretical model was developed using vacancy injection as responsible for mixing.

Measurement of lithium diffusion coefficient in thin metallic multilayer by neutron depth profiling

2020 ◽  
Vol 52 (12) ◽  
pp. 939-942
Author(s):  
Giovanni Ceccio ◽  
Jiri Vacik ◽  
Pavel Horák ◽  
Antonino Cannavò ◽  
Vladimir Hnatowicz
Keyword(s):  
Diffusion Coefficient ◽  
Depth Profiling ◽  
Neutron Depth Profiling ◽  
Lithium Diffusion Coefficient ◽  
Lithium Diffusion

Temperature dependence of oxygen diffusion and consumption in mammalian striated muscle

1993 ◽  
Vol 264 (6) ◽  
pp. H1825-H1830 ◽  
Author(s):  
T. B. Bentley ◽  
H. Meng ◽  
R. N. Pittman
Keyword(s):  
Diffusion Coefficient ◽  
Steady State ◽  
Oxygen Diffusion ◽  
Striated Muscle ◽  
Effect Of Temperature ◽  
Retractor Muscle ◽  
Oxygen Solubility ◽  
Order Of Magnitude

This study investigated the effect of temperature on the oxygen diffusion coefficient (DO2) of hamster retractor muscle from 11 to 37 degrees C. DO2 was measured using a non-steady-state technique, whereas muscle O2 consumption (VO2) was estimated after steady state was reached. DO2 was 0.84 +/- 0.04 x 10(-5) cm2/s at 11 degrees C and rose exponentially to 2.41 +/- 0.19 x 10(-5) cm2/s at 37 degrees C, producing a temperature coefficient for DO2 of 4.60%/degrees C for this temperature range. To measure DO2 directly at 37 degrees C, it was necessary to inhibit tissue VO2 with Amytal. The DO2 measurements made at 37 degrees C were significantly higher than previously reported values, which had been based on extrapolations from lower temperatures (6). Further analysis suggests a possible transition in the diffusion pathway between 23 and 30 degrees C, resulting in a DO2 higher than that previously expected. This larger DO2, together with a recently published value of oxygen solubility (alpha) (21), results in an in vitro Krogh's diffusion coefficient (KO2) that is 2.4 times larger than that previously reported (24) and therefore significantly reduces an order of magnitude discrepancy between in vitro and estimated in vivo KO2 values (24). Muscle VO2 was 0.35 ml O2.min-1.100 g-1 at 11 degrees C and increased with temperature, resulting in an activation energy of the rate-limiting reaction from the Arrhenius equation of -10.5 kcal/mol between 11 and 30 degrees C.

Computer Simulation of Vacancy Segregation at Antiphase Domain Boundaries During Coarsening

1993 ◽  
Vol 319 ◽  
Author(s):  
Long-Qing Chen
Keyword(s):  
Computer Simulation ◽  
Vacancy Concentration ◽  
Antiphase Domain ◽  
Atomic Diffusion ◽  
Domain Boundaries ◽  
Order Of Magnitude ◽  
Segregation Profile ◽  
Computer Simulation Technique ◽  
Antiphase Domains ◽  
Coarsening Kinetics

AbstractA computer simulation technique based on the Master Equation Method (MEM) is developed for modeling the spatial distribution of vacancies during ordering and subsequent domain coalescence and coarsening. A vacancy mechanism is assumed for the atomic diffusion and the single-site approximation is employed. It is demonstrated that vacancies strongly segregate into the antiphase domain boundaries (APBs) during coarsening, resulting in the vacancy concentration at APBs more than an order of magnitude higher than that inside the ordered domains. As the antiphase domains coarsen, the vacancy concentration at the APBs continues to increase and its spatial s segregation profile moves accompanying the APB migration. The effect of vacancy concentration on the antiphase domain coarsening kinetics is discussed.

Rapid Diffusion of Molybdenum Trace Contamination in Silicon

1984 ◽  
Vol 36 ◽  
Author(s):  
S. P. Tobin ◽  
A. C. Greenwald ◽  
R. G. Wolfson ◽  
D. L. Meier ◽  
P. J. Drevinsky
Keyword(s):  
Diffusion Coefficient ◽  
Transition Metals ◽  
Lower Limit ◽  
Minority Carrier ◽  
Diffusion Length ◽  
Deep Level ◽  
Depth Profiling ◽  
Epitaxial Layers ◽  
Epitaxial Silicon ◽  
Rapid Diffusion

ABSTRACTMolybdenum contamination has been detected in silicon epitaxial layers and substrate wafers after processing in any one of several epitaxial silicon reactors. Greatly reduced minority carrier diffusion lengths and lifetimes are consistent with Mo concentrations measured by DLTS in the 1012 and 1013 cm−3 ranges. Depth profiling of diffusion length and the Mo deep level show much greater penetration than expected from previous reports of Mo as a slow diffuser. The data indicate a lower limit of 10−8 cm2/sec for the diffusion coefficient of Mo in silicon at 1200°C, consistent with high diffusivities measured for other transition metals.

Transport of Neutral Solute Across Articular Cartilage: The Role of Zonal Diffusivities

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
V. Arbabi ◽  
B. Pouran ◽  
H. Weinans ◽  
A. A. Zadpoor
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Equilibrium Concentration ◽  
Cartilage Tissue ◽  
Zone Model ◽  
Superficial Zone ◽  
Time Curve ◽  
Order Of Magnitude ◽  
Multizone Model

Transport of solutes through diffusion is an important metabolic mechanism for the avascular cartilage tissue. Three types of interconnected physical phenomena, namely mechanical, electrical, and chemical, are all involved in the physics of transport in cartilage. In this study, we use a carefully designed experimental-computational setup to separate the effects of mechanical and chemical factors from those of electrical charges. Axial diffusion of a neutral solute (Iodixanol) into cartilage was monitored using calibrated microcomputed tomography (micro-CT) images for up to 48 hr. A biphasic-solute computational model was fitted to the experimental data to determine the diffusion coefficients of cartilage. Cartilage was modeled either using one single diffusion coefficient (single-zone model) or using three diffusion coefficients corresponding to superficial, middle, and deep cartilage zones (multizone model). It was observed that the single-zone model cannot capture the entire concentration-time curve and under-predicts the near-equilibrium concentration values, whereas the multizone model could very well match the experimental data. The diffusion coefficient of the superficial zone was found to be at least one order of magnitude larger than that of the middle zone. Since neutral solutes were used, glycosaminoglycan (GAG) content cannot be the primary reason behind such large differences between the diffusion coefficients of the different cartilage zones. It is therefore concluded that other features of the different cartilage zones such as water content and the organization (orientation) of collagen fibers may be enough to cause large differences in diffusion coefficients through the cartilage thickness.

High Resolution Auger Depth Profiles Using a Dual Ion Gun System

1985 ◽  
Vol 54 ◽  
Author(s):  
S. Ingrey ◽  
J.P.D. Cook
Keyword(s):  
Electron Beam ◽  
Depth Profiling ◽  
Depth Resolution ◽  
Grazing Incidence ◽  
Low Energy ◽  
Multilayer Structures ◽  
Dramatic Decrease ◽  
Depth Profiles ◽  
Order Of Magnitude ◽  
Magnitude Improvement

A dual ion gun system has been proposed (D.E. Sykes et al, Appl. Surf. Sci. 5(1980)103) to reduce texturing and improve depth resolution during Auger sputter depth profiling. We have evaluated this ion gun configuration by profiling a variety of multilayer structures. With careful alignment of the guns, we have obtained a dramatic decrease in ion-induced texturing often seen when a single ion gun is used. This effect was particularly pronounced for polycrystalline Al films on Si where an order of magnitude improvement in depth resolution was achieved. Further refinements of the technique include the use of low energy (IkeV) grazing incidence xenon ions and a small electron beam probe area. Depth profiles obtained from Ni/Cr, W/Si, and GaAs/GaAlAs multilayer structures will also be discussed.

Thermal diffusion of Helium and volatil fission products in UO2 and zirconolite nuclear ceramics

2004 ◽  
Vol 824 ◽  
Author(s):  
Danièle Roudil ◽  
Xavier Deschanels ◽  
Patrick Trocellier ◽  
Fran ç ois Jomard ◽  
Annick Boutry ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Thermal Diffusion ◽  
Uranium Dioxide ◽  
Experimental Studies ◽  
Fission Products ◽  
Spent Fuel ◽  
Fuel Storage ◽  
Order Of Magnitude ◽  
Interim Storage ◽  
Helium Diffusion

AbstractThe behaviour and diffusion mechanisms of helium in nuclear ceramics, such as uranium dioxide spent fuel matrix and zirconolite for the specific conditioning of minor actinides, significantly impact the possible evolution of those matrices in interim storage or disposal conditions. In the framework of spent fuel storage studies, the additional diffusion of gas and fission products in uranium dioxidematrix is also an essential aspect of the R&D. Specific experimental studies have been conducted, devoted to thermal diffusion under 1000 C. Data processing methods, lead to helium diffusion coefficient and associated activation energy of 1.05 eV in the zirconolite and 2 eV in UO2. Comparativelywith the uranium dioxide matrix, the helium diffusion coefficient in zirconolite is 1 to 100 million times higher; this parameter will have to be taken into account to dimension the waste form. Diffusion coefficients measurements between 800 C and 1000 C, investigated by SIMS, showed a very slow diffusion of volatile fission products Xe, I, Te and Cs, with coefficients two or three order of magnitude lower than for helium.

A New Approach for the Diffusion Coefficient Evaluation of Sulfur in CaO-SiO2-Al2O3 Slag

2011 ◽  
Vol 312-315 ◽  
pp. 626-634
Author(s):  
Luckman Muhmood ◽  
Nurini N. Viswanathan ◽  
Seshadri Seetharaman
Keyword(s):  
Diffusion Coefficient ◽  
Sulfide Capacity ◽  
Chemical Diffusion ◽  
Partition Ratio ◽  
Critical Parameters ◽  
New Approach ◽  
Matlab Program ◽  
Order Of Magnitude ◽  
Concentration Changes ◽  
Silver Metal

The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO- 9.6% SiO2- 38.9% Al2O3 was measured at 1723 K by chemical diffusion from the variation of concentration of sulfur in silver metal. A MATLAB program was developed to find the concentration variation of sulfur in silver metal using various critical parameters like the diffusion coefficient of sulfur in slag available in literature, sulfur partition ratio, sulfide capacity of the slag and the its density. The PS2 and PO2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS and confirming the same by using ThermoCalc. The density of the slag at 1723 K was obtained from earlier experiments. Initially the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration changes of Sulfur obtained from the program agreed with the experimental results. The diffusion coefficient of sulfur in 51.5% CaO- 9.6% SiO2- 38.9% Al2O3 slag at 1723 K was estimated as 4.14x10-6 cm2/sec.

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