Modeling of the Transition From Active to Passive Oxidation of Si(100)

2000 ◽  
Vol 619 ◽  
Author(s):  
Da-Jiang Liu ◽  
Cheol Ho Choi ◽  
Mark S. Gordon ◽  
J.W. Evans
Keyword(s):  
Oxide Film ◽  
Quantum Chemistry ◽  
Surface Temperature ◽  
Ab Initio ◽  
Lattice Gas ◽  
Cooperative Behavior ◽  
Active Oxidation ◽  
Island Formation ◽  
Passive Oxidation ◽  
Lattice Gas Models

ABSTRACTFor a Si(100)2×1 surface exposed to oxygen, there is a transition from etching (“active” oxidation via removal of SiO) to “passive” oxidation (buildup of an oxide film) with decreasing surface temperature. The transition depends sensitively on a competition between SiO desorption, and oxide island formation. We analyze these processes utilizing both ab-initio quantum chemistry studies of key energetics and lattice-gas models for the cooperative behavior.

scholarly journals Cooperative Behavior of Kinetically Constrained Lattice Gas Models of Glassy Dynamics

2005 ◽  
Vol 120 (1-2) ◽  
pp. 167-238 ◽  
Author(s):  
Cristina Toninelli ◽  
Giulio Biroli ◽  
Daniel S. Fisher
Keyword(s):  
Lattice Gas ◽  
Cooperative Behavior ◽  
Glassy Dynamics ◽  
Lattice Gas Models

SILICON OXIDE DECOMPOSITION AND DESORPTION DURING THE THERMAL OXIDATION OF SILICON

1999 ◽  
Vol 06 (01) ◽  
pp. 45-52 ◽  
Author(s):  
D. STARODUB ◽  
E. P. GUSEV ◽  
E. GARFUNKEL ◽  
T. GUSTAFSSON
Keyword(s):  
Oxide Film ◽  
Thermal Oxidation ◽  
Silicon Oxide ◽  
Film Growth ◽  
Active Oxidation ◽  
Passive Oxidation ◽  
Wide Range ◽  
Volatile Products ◽  
Higher Temperature ◽  
Lower Temperature

The thermal oxidation of silicon is normally considered to occur via two different routes. At higher O 2 pressures and lower temperature SiO 2 (s) film growth occurs ("passive" oxidation), while at lower O 2 pressures and higher temperature SiO(g) is desorbed in an etching process ("active" oxidation). We have measured the yield of SiO into the gas phase in a wide range of dry O 2 pressures (10-7–10-5 Torr) and Si substrate temperatures (620–870°C) in the passive as well as the active oxidation regimes. A phase diagram for silicon oxidation in this pressure–temperature region is obtained. We have found evidence for small but measurable yields of SiO(g) desorbing from the nascent oxide film during the initial stages of passive oxidation, even when the oxide film continuously covers the surface. A sensitive method for detecting volatile products based on condensation of desorbed species is described.

Thermodynamic Data of Iodine Reactions Calculated by Quantum Chemistry. Training Set of Molecules

2008 ◽  
Vol 73 (10) ◽  
pp. 1340-1356 ◽  
Author(s):  
Katarína Mečiarová ◽  
Laurent Cantrel ◽  
Ivan Černušák
Keyword(s):  
Quantum Chemistry ◽  
Ab Initio ◽  
Thermodynamic Data ◽  
Theoretical Calculations ◽  
Reactor Core ◽  
Fission Products ◽  
Vapour Phase ◽  
Reactor Accident ◽  
Training Set ◽  
Coolant System

This paper focuses on the reactivity of iodine which is the most critical radioactive contaminant with potential short-term radiological consequences to the environment. The radiological risk assessments of 131I volatile fission products rely on studies of the vapour-phase chemical reactions proceeding in the reactor coolant system (RCS), whose function is transferring the energy from the reactor core to a secondary pressurised water line via the steam generator. Iodine is a fission product of major importance in any reactor accident because numerous volatile iodine species exist under reactor containment conditions. In this work, the comparison of the thermodynamic data obtained from the experimental measurements and theoretical calculations (approaching "chemical accuracy") is presented. Ab initio quantum chemistry methods, combined with a standard statistical-thermodynamical treatment and followed by inclusion of small energetic corrections (approximating full configuration interaction and spin-orbit effects) are used to calculate the spectroscopic and thermodynamic properties of molecules containing atoms H, O and I. The set of molecules and reactions serves as a benchmark for future studies. The results for this training set are compared with reference values coming from an established thermodynamic database. The computed results are promising enough to go on performing ab initio calculations in order to predict thermo-kinetic parameters of other reactions involving iodine-containing species.

Vibrational branching ratios and radiative lifetimes in the laser cooling of AlBr

2017 ◽  
Vol 19 (7) ◽  
pp. 5519-5524 ◽  
Author(s):  
Yufeng Gao ◽  
Mingjie Wan
Keyword(s):  
Quantum Chemistry ◽  
Ab Initio ◽  
Laser Cooling ◽  
Branching Ratios ◽  
Radiative Lifetimes

The feasibility of laser cooling of the AlBr molecule is investigated usingab initioquantum chemistry.

scholarly journals iSPECTRON : A simulation interface for linear and nonlinear spectra with ab‐initio quantum chemistry software

2021 ◽  
Vol 42 (9) ◽  
pp. 644-659 ◽  
Author(s):  
Francesco Segatta ◽  
Artur Nenov ◽  
Daniel R. Nascimento ◽  
Niranjan Govind ◽  
Shaul Mukamel ◽  
...  
Keyword(s):  
Quantum Chemistry ◽  
Ab Initio ◽  
Linear And Nonlinear

TRANSFER-MATRIX STUDY OF NEGATIVE-FUGACITY SINGULARITY OF HARD-CORE LATTICE GAS

1999 ◽  
Vol 10 (04) ◽  
pp. 517-529 ◽  
Author(s):  
SYNGE TODO
Keyword(s):  
Large Scale ◽  
Lattice Gas ◽  
Central Charge ◽  
Hard Core ◽  
Universality Class ◽  
Two Dimensions ◽  
Square Lattice ◽  
Lattice Gas Models ◽  
Renormalization Technique ◽  
Phenomenological Renormalization

A singularity on the negative-fugacity axis of the hard-core lattice gas is investigated in terms of numerical diagonalization of large-scale transfer matrices. For the hard-square lattice gas, the location of the singular point [Formula: see text] and the critical exponent ν are accurately determined by the phenomenological renormalization technique as -0.11933888188(1) and 0.416667(1), respectively. It is also found that the central charge c and the dominant scaling dimension xσ are -4.399996(8) and -0.3999996(7), respectively. Similar analyses for other hard-core lattice-gas models in two dimensions are also performed, and it is confirmed that the universality between these models does hold. These results strongly indicate that the present singularity belongs to the same universality class as the Yang–Lee edge singularity.

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