Role of oxygen in surface kinetics of SiO2 growth on single crystal SiC at elevated temperatures

2021 ◽  
Vol 47 (2) ◽  
pp. 1855-1864
Author(s):  
Yongjie Zhang ◽  
Shaoxiang Liang ◽  
Yi Zhang ◽  
Rulin Li ◽  
Zhidong Fang ◽  
...  
Keyword(s):  
Single Crystal ◽  
Elevated Temperatures ◽  
Surface Kinetics ◽  
Single Crystal Sic ◽  
Kinetics Of

Equilibration kinetics of TiO2 single crystal at elevated temperatures

2005 ◽  
Vol 242 (11) ◽  
pp. R91-R93 ◽  
Author(s):  
J. Nowotny ◽  
T. Bak ◽  
M. K. Nowotny ◽  
C. C. Sorrell
Keyword(s):  
Single Crystal ◽  
Elevated Temperatures ◽  
Kinetics Of

Steps of Surface Etching and Carbon Deposition on the Graphite Basal Plane

1993 ◽  
Vol 312 ◽  
Author(s):  
Xi Chu ◽  
Vincent Chan ◽  
Lanny D. Schmidt
Keyword(s):  
Single Crystal ◽  
Vapor Deposition ◽  
Basal Plane ◽  
Carbon Deposition ◽  
Chemical Vapor ◽  
Reaction Rates ◽  
Plane Versus ◽  
Graphite Basal Plane ◽  
Kinetics Of

AbstractThe reactions of O2, H2O, CO2, NO2, NO, and N2O with single crystal graphite between 400 and 700°C have been studied by STM to obtain quantitative kinetics by measuring the number and size of monolayer pits on the basal plane versus temperature and time. At low temperature the reaction initiates exclusively from the point defects on the basal plane to form monolayer pits. The shape of the monolayer pits vary from nearly triangular to hexagonal to circular depending on the rate of the reaction and the reacting gases. The sizes of the monolayer pits grow linearly with reacting time. The monolayer reaction rates follow the order of RNO2 > RN2O > RNO > RO2 > RH2O > RCO2. The activation energies for reactions with O2, H2O, NO2, NO, and N2O, are determined to be 127, 205, 60, 89, and 74 kJ/mol respectively.Carbon deposition from hydrocarbons onto surfaces of single crystal graphite has been examined to study the fundamental steps of chemical vapor deposition. Uniform monolayer pits on graphite surface were first produced by reactive etching of freshly cleaved single crystal of graphite in oxygen and carbon was then made to deposit exclusively on these defects in the basal plane. Carbon vapor deposition forms unique structures around the monolayer steps. By measuring the sizes of structures on steps in various gases versus temperature and pressure, the kinetics of hydrocarbon decomposition and the role of surface diffusion can be determined.

Kinetics of the self-assembly of bold alpha -cyclodextrin [2]pseudorotaxanes with polymethylene threads bearing quaternary ammonium and phosphonium end groups

1998 ◽  
Vol 76 (6) ◽  
pp. 843-850
Author(s):  
Angela P Lyon ◽  
Nicola J Banton ◽  
Donal H Macartney
Keyword(s):  
Rate Constant ◽  
Self Assembly ◽  
Elevated Temperatures ◽  
Formation Rate ◽  
Minor Effect ◽  
Prolonged Heating ◽  
End Groups ◽  
A Minor ◽  
Kinetics Of

The kinetics and mechanism of the formation and dissociation of a series of [2]pseudorotaxanes, comprised of α -cyclodextrin (α -CD) as the cyclic component and the ([Me3N(CH2)nNMe3]2+ (n = 8-12), [Me2EtN(CH2)10NEtMe2]2+, and [Me3P(CH2)10PMe3]2+) dications as the threads, were determined by means of 1H and 31P NMR in aqueous solution. The length of the polymethylene chain (n) of the thread, which has a minor effect on the rate constant for pseudorotaxane formation, is important in the kinetics of the dissociation reactions, with the longer, more hydrophobic chains resulting in slower pseudorotaxane dissociation. The replacement of one methyl substitutent by an ethyl group in each of the end groups on the [Me3N(CH2)10NMe3]2+ thread results in a 30-fold decrease in the formation rate constant. Replacements, by ethyls, of two or all of the methyl substitutents prevent the formation of the pseudorotaxane, even after prolonged heating. The pseudorotaxane containing the {Me3P(CH2)10PMe3.; α-CD}2+ thread forms only at elevated temperatures by a slippage mechanism, and the rate constant for its self-assembly at 75°C (8 x 10-5 M-1 s-1) is more than 106 smaller than the rate constant at 75°C (200 M-1 s-1) extrapolated for the corresponding {Me3N(CH2)10NMe3 . α -CD}2+complex. The enthalpies and entropies of activation for the formation and dissociation of the [2]pseudorotaxanes decrease with an increase in the size and hydrophobicity of the end groups, suggesting a reduced role of desolvation of the quaternized atoms in the threading or dethreading processes.Key words: pseudorotaxane, α -cyclodextrin, kinetics, self-assembly, slippage, supramolecular.

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.

Growth of Epitaxial CoSi2 Through a Thin Interlayer

1996 ◽  
Vol 427 ◽  
Author(s):  
R. T. Tung
Keyword(s):  
Thin Films ◽  
Aqueous Solution ◽  
Thin Layer ◽  
Single Crystal ◽  
Epitaxial Growth ◽  
Elevated Temperatures ◽  
Time Process ◽  
Thin Interlayer ◽  
Technological Interest

AbstractThe phenomenon of Ti-interlayer mediated epitaxy (TIME) of CoSi2 on Si(100) has attracted much academic and technological interest. As yet, the role of the interlayer, Ti, is not fully understood. The various drawbacks of the TIME process have driven the search for a better interlayer. New results are presented which demonstrate the efficacy of a thin SiOx layer, grown in a peroxide-containing aqueous solution, in inducing nearly perfect epitaxial growth of CoSi2 on practically all surfaces of Si. This technique, dubbed oxide mediated epitaxy (OME), allows a thin layer of epitaxial CoSi2 to grow sub-surface, leaving the SiOx layer largely on the surface of the silicide. An interesting result of the surface oxide cap is a significant re-evaporation of cobalt observed during deposition at elevated temperatures. Thicker (10-30nm), excellent quality, CoSi2 single crystal thin films have been grown by repeated growth sequences on Si(100), (110), (211) and (511). Nearly perfect type A oriented CoSi2 layers were grown on Si(111) using mixed A/B oriented template layers.

Influence of Growth Temperature on the Evolution of Dislocations during PVT Growth of Bulk SiC Single Crystals

2007 ◽  
Vol 556-557 ◽  
pp. 263-266
Author(s):  
Sakwe Aloysius Sakwe ◽  
Peter J. Wellmann
Keyword(s):  
Optical Microscopy ◽  
Single Crystals ◽  
Growth Temperature ◽  
Growth Front ◽  
Growth Surface ◽  
Surface Kinetics ◽  
Step Structure ◽  
Temperature Regimes ◽  
Kinetics Of

In this paper we report, based on analysis of dislocation statistics, on the influence of growth temperature on the nucleation, propagation and annihilation mechanisms of dislocations. Using KOH defect etching and optical microscopy we have conducted dislocation tracking along lengths of crystals grown under various process temperature regimes to study their evolution and propagation mechanisms statistically. We further present the influence of growth temperature on the step structure of the growth front using AFM measurements. From the analysis of dislocation statistics and step structure in relation to temperature we derive the role of surface kinetics of the SiC gas species on the growth surface in dislocation evolution during PVT growth of bulk SiC.

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