Electronic Stopping Power for Low Energy Ions

1985 ◽  
Vol 45 ◽  
Author(s):  
N. Azziz ◽  
K. W. Brannon ◽  
G. R. Srinivasan
Keyword(s):  
Effective Charge ◽  
Density Functional ◽  
Considerable Effect ◽  
Low Energy ◽  
Stopping Power ◽  
Target Electron ◽  
Functional Formalism ◽  
Low Energy Ions ◽  
Electronic Stopping Power

ABSTRACTA procedure to be used in ion implantation calculations has been developed to determine the stopping power of an ion at low energy as a function of its effective charge. The ion effective charge accounts for screening of the ion and has been found to have considerable effect on the stopping power through its dependence on the target electron density. Steps in the procedure include: the calculation of the Fermi momentum of the target, calculation of the relative velocity between the projectile and target electron cloud, determination of the screening distance for the ion, and calculation of the proton stopping power Sp according to the density-functional formalism. The ion stopping power is then is the ion effective charge. The procedure can be applied to semiconductors and metals. Comparisons are reported with the predictions of the Firsov and Lindhard methods which do not include any effective charge or shell structure considerations. The computer program MARLOWE has been modified to include this method for calculating the stopping power. Results in the form of implanted boron profiles in silicon will be presented.

Accurate determination of band gaps within density functional formalism

2013 ◽  
Vol 87 (23) ◽  
Author(s):  
Prashant Singh ◽  
Manoj K. Harbola ◽  
Biplab Sanyal ◽  
Abhijit Mookerjee
Keyword(s):  
Density Functional ◽  
Accurate Determination ◽  
Band Gaps ◽  
Functional Formalism

SURFACE SENSITIVITY OF VERY LOW ENERGY ELECTRONS

1999 ◽  
Vol 06 (05) ◽  
pp. 631-633 ◽  
Author(s):  
I. BARTOŠ ◽  
W. SCHATTKE
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Quantitative Description ◽  
Low Energy ◽  
Imaginary Component ◽  
Functional Formalism ◽  
Self Energy ◽  
Surface Sensitivity ◽  
Escape Depth ◽  
Low Energies

The surface sensitivity of electron diffraction and of electron spectroscopies is determined by the imaginary component of the electron self-energy. In crystals, the energy and direction dependence of the electron attenuation and of the escape depth should be taken into account at very low energies. Strong anisotropy of the electron attenuation has been obtained around 20 eV from peak shapes in VLEED intensity profiles from (111) transition metal surfaces. Extension of the local density approximation in the density functional formalism provides quantitative description of the electron self-energy. The one-step model of angular resolved photoemission incorporating the self-energy predicts a strong energy and angle dependence of the escape depth of low energy photoelectrons emitted from GaAs(110).

A New Local Electronic Stopping Model for the Monte Carlo Simulation of Arsenic Ion Implantation into (100) Single-Crystal Silicon

1995 ◽  
Vol 389 ◽  
Author(s):  
S.-H. Yang ◽  
S. Morris ◽  
S. Tian ◽  
K. Parab ◽  
A. F. Tasch ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Ion Implantation ◽  
Single Crystal ◽  
Density Functional ◽  
Single Crystal Silicon ◽  
Stopping Power ◽  
Crystal Silicon ◽  
Electronic Density ◽  
New Model ◽  
Electronic Stopping Power

ABSTRACTIn this paper is reported the development and implementation of a new local electronic stopping model for arsenic ion implantation into single-crystal silicon. Monte Carlo binary collision (MCBC) models are appropriate for studying channeling effects since it is possible to include the crystal structure in the simulators. One major inadequacy of existing MCBC codes is that the electronic stopping of implanted ions is not accurately and physically accounted for, although it is absolutely necessary for predicting the channeling tails of the profiles. In order to address this need, we have developed a new electronic stopping power model using a directionally dependent electronic density (to account for valence bonding) and an electronic stopping power based on the density functional approach. This new model has been implemented in the MCBC code, UT-MARLOWE The predictions of UT-MARLOWE with this new model are in very good agreement with experimentally-measured secondary ion mass spectroscopy (SIMS) profiles for both on-axis and off-axis arsenic implants in the energy range of 15-180 keV.

scholarly journals Determination of the Effect of Chalcogen Replacement on the Interaction Site and Transition State of the Substituted Analogues of Formaldehyde with Aldehyde Oxidase: A Density Functional Theory Approach

2019 ◽  
pp. 25-42
Author(s):  
Tadege Belay
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Active Site ◽  
Density Functional ◽  
Aldehyde Oxidase ◽  
Theory Approach ◽  
Functional Formalism ◽  
Functional Theory ◽  
Reported Data

Aldehyde oxidase (AO) enzyme is known to oxidize aldehydes. One of the aldehydes, formaldehyde, is known to inhibit xanthine oxidase as it turns over. However, there is no reported data whether it behaves the same when it reacts with aldehyde oxidase. Similarly, the effect of chalcogen replacement on nucleophilic reaction and charge density distribution on the substituted analogs of formaldehyde and their behavior during catalysis has never been studied. Therefore, the research is intended to probe the most tractable substrate that interacts to the reductive half-reaction active site of AO. Therefore, a density functional theory of the B3LYP correlation functional formalism (DFT-B3LYP) methods was used to generate several parameters from the electronic structure calculations. Accordingly, the higher percentage (%) contribution to HOMO and energy barrier (kcal/mol) (0.099, -7.185040E+04) makes formaldehyde as the favored substrate for aldehyde oxidase, compared to thioformaldehyde (-0.245, -2.745113E+05) and selenoformaldehyde (-0.175, -1.529992E+06), respectively. In addition, the transition state structures for the active site bound to formaldehyde (ACT-FA), thioformaldehyde (ACT-THIO FA), and selenoformaldehyde (ACT-SELENO FA), respectively, were confirmed by one imaginary negative frequency (S-1) (-328.44, -430.266, and -624.854).

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