Low Energy Ion Bombardment and Microstructural Evolution in Thin Films

1989 ◽  
Vol 157 ◽  
Author(s):  
Chih M. Yang ◽  
Harry A. Atwater
Keyword(s):  
Thin Films ◽  
Ion Bombardment ◽  
Island Growth ◽  
New Approach ◽  
Enhanced Diffusion ◽  
Rate Laws ◽  
Island Evolution ◽  
Diffusion Limited ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTA new approach to modeling the evolution of islands in thin films by growth and coarsening during ion bombardment is described. Solution of a continuity equation and matter conservation relation, coupled with interface-limited and diffusion-limited rate laws for island growth and coarsening allows the kinetics of island evolution to be modeled. Results from the model indicate distinct kinetic paths for island evolution during ion bombardment as a result of growth, enhanced diffusion, island dissociation and monomer sputtering.

Ion Beam Mixing of Ni-Ti Bilayered Thin Films

1985 ◽  
Vol 43 ◽  
pp. 290-291
Author(s):  
A. K. Rai ◽  
R. S. Bhattacharya ◽  
M. H. Rashid
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Amorphous Alloys ◽  
Ion Beam ◽  
Ion Bombardment ◽  
High Energy ◽  
Mixing Efficiency ◽  
Ion Beam Mixing ◽  
Enhanced Diffusion ◽  
Binary Metal

Ion beam mixing has recently been found to be an effective method of producing amorphous alloys in the binary metal systems where the two original constituent metals are of different crystal structure. The mechanism of ion beam mixing are not well understood yet. Several mechanisms have been proposed to account for the observed mixing phenomena. The first mechanism is enhanced diffusion due to defects created by the incoming ions. Second is the cascade mixing mechanism for which the kinematicel collisional models exist in the literature. Third mechanism is thermal spikes. In the present work we have studied the mixing efficiency and ion beam induced amorphisation of Ni-Ti system under high energy ion bombardment and the results are compared with collisional models. We have employed plan and x-sectional veiw TEM and RBS techniques in the present work.

The Anomalous Diffusion-limited Reaction Kinetics of a Phototrapping Reaction

1996 ◽  
Vol 464 ◽  
Author(s):  
Eric Monson ◽  
Anna L. Lin ◽  
Raoul Kopelman
Keyword(s):  
Laser Beam ◽  
Two Dimensions ◽  
One Dimensional ◽  
Rate Laws ◽  
Diffusion Limited ◽  
Dimensional Diffusion ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
Diffusion Limited Reaction ◽  
Classical Constant

AbstractA focused laser beam acts as both a “phototrap”, bleaching fluorophore molecules which diffuse into the beam path, and as a confocal probe, detecting the excited, unbleached fluorophore molecules still present in the trap. With this focused laser beam, we observe anomalous asymptotic rate laws similar to those predicted for a diffusion-controlled elementary trapping reaction, A + T → T, in one and two dimensions. One dimensional diffusion-limited trapping kinetics are approached in capillaries with 10 μm diameters while two dimensional diffusion limited trapping kinetics are observed with unstirred samples having a quasi 2-D geometry. In the presence of stirring, the 2-D samplesexhibit the classical, constant trapping rate over time.

Preparation of SrTiO3 Thin Films by Ecr and Thermal Mocvd

1993 ◽  
Vol 310 ◽  
Author(s):  
P-Y. Lesaicherre ◽  
H. Yamaguchi ◽  
T. Sakuma ◽  
Y. Miyasaka ◽  
M. Yoshida ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Reaction ◽  
Columnar Structure ◽  
Thermal Cvd ◽  
Diffusion Limited ◽  
Maximum Dielectric Constant ◽  
And Diffusion ◽  
Ti Content ◽  
Limited Process ◽  
Sem Analyses

AbstractSrTiO3 thin films were prepared by ECR and thermal MOCVD. In thermal-CVD mode, Sr content and Ti content were at a maximum at 0.56 Torr. Results showed that SrO deposition is a surface reaction limited process between 500 and 650°C, whereas TiO2 deposition is surface reaction limited between 500 and 600 °C, and diffusion limited above 600 °C. At a low pressure of 8 mTorr, ECR oxygen plasma was found to help decompose Ti(i-OC3H7)4. In ECR-CVD mode, the deposition temperature could be lowered to 400 °C. TEM and SEM analyses showed that SrTiO3 thin films have a columnar structure. The size of the grains depends on film thickness, and their shape on film composition (Sr/Ti ). Films prepared by thermal-CVD had a lateral step coverage of 50 %. 40 nm SrTiO3 thin films (Sr/Ti = 1.0) prepared by thermal-CVD on Pt/TaOx/Si and annealed for 2 hours in O2 had a maximum dielectric constant of 139 (Cs = 31 fF/μm2 and teq = 1.1 nm) and a leakage current density of 6x10−8 A/cm2 at 1.0 V.

scholarly journals Fast oxygen exchange and diffusion kinetics of grain boundaries in Sr-doped LaMnO3 thin films

2015 ◽  
Vol 17 (12) ◽  
pp. 7659-7669 ◽  
Author(s):  
Edvinas Navickas ◽  
Tobias M. Huber ◽  
Yan Chen ◽  
Walid Hetaba ◽  
Gerald Holzlechner ◽  
...  
Keyword(s):  
Thin Films ◽  
Oxygen Reduction Reaction ◽  
Grain Boundaries ◽  
Isotope Exchange ◽  
Reduction Reaction ◽  
Diffusion Kinetics ◽  
Ion Diffusion ◽  
Kinetics Of ◽  
And Diffusion ◽  
Oxide Ion

Isotope exchange depth profile measurements were performed on columnar/epitaxial LSM thin films with varied microstructure. These uncover the importance of grain boundaries for oxygen reduction reaction and oxide ion diffusion.

Irradiation-enhanced diffusion and diffusion-limited creep in U3Si2

2021 ◽  
pp. 153129
Author(s):  
M.W.D. Cooper ◽  
K.A. Gamble ◽  
L. Capolungo ◽  
C. Matthews ◽  
D.A. Andersson ◽  
...  
Keyword(s):  
Enhanced Diffusion ◽  
Diffusion Limited ◽  
And Diffusion ◽  
Limited Creep

Influence of Electrolytes and Humic Acid on Aggregation Behavior of C60 Nanoparticles in Aquatic System

2013 ◽  
Vol 448-453 ◽  
pp. 48-51
Author(s):  
Hua Fang ◽  
Bing Bing Shen ◽  
Yu Xin Sun ◽  
Yuan Wang ◽  
Ji Lai Lu
Keyword(s):  
Humic Acid ◽  
Colloidal Stability ◽  
Dlvo Theory ◽  
Aquatic Environments ◽  
Aggregation Kinetics ◽  
Time Resolved ◽  
Diffusion Limited ◽  
Wide Range ◽  
Kinetics Of ◽  
And Diffusion

The aggregation kinetics of C60 nanoparticles have been investigated over a wide range of monovalent and divalent electrolyte concentrations by employing time-resolved dynamic light scattering (DLS). The results showed that the presence of electrolyte made a dramatic decrease in the surface zeta potential and increase in the particle size. The aggregation kinetics of C60 nanoparticles exhibited reaction-limited and diffusion-limited regimes, which was found to be consistent with the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. The critical coagulation concentration (CCC) values of C60 nanoparticles were estimated as 321mM Na+, 295mM K+, 9.6mM Ca2+and 6.7mM Mg2+, which were far higher than the electrolyte concentrations in natural water. The enhanced C60 stability in the presence of humic acid was attributable to steric repulsion. Therefore C60 nanoparticles can be relatively stable in typical aquatic environments.

scholarly journals Investigation into mechanisms and kinetics of asphaltene aggregation in toluene/n-hexane mixtures

2019 ◽  
Vol 17 (2) ◽  
pp. 457-466
Author(s):  
Bahram Soltani Soulgani ◽  
Fatemeh Reisi ◽  
Fatemeh Norouzi
Keyword(s):  
Image Processing ◽  
Fractal Theory ◽  
Particle Growth ◽  
Force Balance ◽  
Asphaltene Precipitation ◽  
Diffusion Limited Aggregation ◽  
Model Calculations ◽  
Diffusion Limited ◽  
Kinetics Of ◽  
And Diffusion

Abstract Determining the rate of asphaltene particle growth is one of the main problems in modeling of asphaltene precipitation and deposition. In this paper, the kinetics of asphaltene aggregation under different precipitant concentrations have been studied. The image processing method was performed on the digital photographs that were taken by a microscope as a function of time to determine the asphaltene aggregation growth mechanisms. The results of image processing by MATLAB software revealed that the growth of asphaltene aggregates is strongly a function of time. Different regions could be recognized during asphaltene particle growth including reaction- and diffusion-limited aggregation followed by reaching the maximum asphaltene aggregate size and start of asphaltene settling and the final equilibrium. Modeling has been carried out to predict the growth of asphaltene particle size based on the fractal theory. General equations have been developed for kinetics of asphaltene aggregation for reaction-limited aggregation and diffusion-limited aggregation. The maximum size of asphaltene aggregates and settling time were modeled by using force balance, acting on asphaltene particles. Results of modeling show a good agreement between laboratory measurements and model calculations.

Metamorphic reaction rate laws and development of isograds

1986 ◽  
Vol 50 (357) ◽  
pp. 359-373 ◽  
Author(s):  
Antonio C. Lasaga
Keyword(s):  
Diffusion Processes ◽  
Relative Role ◽  
Mineral Surfaces ◽  
Surface Kinetics ◽  
Rate Laws ◽  
Careful Treatment ◽  
Reaction Zones ◽  
Kinetics Of ◽  
And Diffusion

AbstractNew data on the kinetics of dehydration of muscovite + quartz suggest the necessity for a careful treatment of both surface kinetics and diffusion processes in metamorphic reactions. A new model is proposed that illustrates the relative role of diffusion and surface reactions in the overall metamorphic process. The rate law for the reaction at mineral surfaces derived from the experimental data is shown to be probably non-linear and similar to rate laws derived from Monte Carlo calculations. The experimental rate data is then used in a heat flow calculation to model the evolution of the muscovite isograd in the field. The position of the isograd, the temperature oversteps above equilibrium, and the width of ‘reaction zones’ are then analysed as a function of intrusion size and kinetic parameters.

Evaluation of substrate uptake by microbial film in a gel-like medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Substrate Uptake ◽  
Limited Region ◽  
Diffusion Limited ◽  
Incremental Value ◽  
Microbial Film ◽  
C And N ◽  
The Relationship ◽  
Kinetics Of ◽  
And Diffusion ◽  
Large Diffusion

Mathematical model was developed to demonstrates the predominantly reaction controlled region and diffusion limited region for p 3 with high or large diffusion in this case, but when p = 0.3 the chemical reaction and diffusion onset occurred. The model developed illustrates the relationship between K₃C* and N/Nmax for various incremental steps of K2 L. The result obtained reveals that increase in K3C* resulted to an increase in N/ Nmax until an optimum value of N/Nmax was achieved after then the values remain constant with incremental value on K3C*. The Kinetics of substrate is dependent of K3C* as well as K2L values of the system, which in overall influence the substrate uptake by microbial film in gel- like medium.

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