Negative-U Properties for Point Defects in Silicon

1980 ◽  
Vol 2 ◽  
Author(s):  
G. D. Watkins
Keyword(s):  
Experimental Evidence ◽  
Point Defects ◽  
Electron Irradiation ◽  
Correlation Energy ◽  
Energy Levels ◽  
Unusual Property ◽  
Simple Point ◽  
Normal Order ◽  
Defect Energy ◽  
Lattice Vacancy

ABSTRACTA defect has negative-U properties if it can trap two electrons (or holes) with the second bound more strongly than the first. It is as if there were a net attraction between the two carriers (negative Hubbard correlation energy U) at the defect, and the defect energy levels in the gap are therefore inverted from their normal order. Experimental evidence is presented that interstitial boron and the lattice vacancy, both common simple point defects produced by electron irradiation of silicon, have this unusual property. These defects represent the first and only concrete examples of negative-U centers in any material and serve as models for an understanding of the phenomenon.

scholarly journals The Effect of Defect Disorder on the Electronic Structure of Rutile TiO2-x

2006 ◽  
Vol 251-252 ◽  
pp. 1-12 ◽  
Author(s):  
Faruque M. Hossain ◽  
Graeme E. Murch ◽  
L. Sheppard ◽  
Janusz Nowotny
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Point Defects ◽  
Density Functional ◽  
Defect Formation ◽  
Energy Levels ◽  
Defect Energy ◽  
Defect Disorder ◽  
Effect Of Oxygen ◽  
Formation Energies

The purpose of this work is to study the effect of bulk point defects on the electronic structure of rutile TiO2. The paper is focused on the effect of oxygen nonstoichiometry in the form of oxygen vacancies, Ti interstitials and Ti vacancies and related defect disorder on the band gap width and on the local energy levels inside the band gap. Ab initio density functional theory is used to calculate the formation energies of such intrinsic defects and to detect the positions of these defect induced energy levels in order to visualize the tendency of forming local mid-gap bands. Apart from the formation energy of the Ti vacancies (where experimental data do not exist) our calculated results of the defect formation energies are in fair agreement with the experimental results and the defect energy levels consistently support the experimental observations. The calculated results indicate that the exact position of defect energy levels depends on the estimated band gap and also the charge state of the point defects of TiO2.

Identifying defect energy levels using DLTS under different electron irradiation conditions

2017 ◽  
Vol 28 (12) ◽  
Author(s):  
Chun-Sheng Guo ◽  
Ruo-Min Wang ◽  
Yu-Wei Zhang ◽  
Guo-Xi Pei ◽  
Shi-Wei Feng ◽  
...  
Keyword(s):  
Electron Irradiation ◽  
Energy Levels ◽  
Defect Energy

Migration energies of point defects during electron irradiation of hydrogenated Si crystals

2002 ◽  
Vol 66 (15) ◽  
Author(s):  
M. Suezawa ◽  
Y. Takada ◽  
T. Tamano ◽  
R. Taniguchi ◽  
F. Hori ◽  
...  
Keyword(s):  
Point Defects ◽  
Electron Irradiation

scholarly journals New Perspective on Formation Energies and Energy Levels of Point Defects in Nonmetals

2012 ◽  
Vol 108 (6) ◽  
Author(s):  
R. Ramprasad ◽  
H. Zhu ◽  
Patrick Rinke ◽  
Matthias Scheffler
Keyword(s):  
Point Defects ◽  
Energy Levels ◽  
New Perspective ◽  
Formation Energies

scholarly journals First Principles Predictions of Intrinsic Defects in Aluminum Arsenide, AlAs

2011 ◽  
Vol 1370 ◽  
Author(s):  
Peter A. Schultz
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Density Functional ◽  
Semiconductor Device ◽  
Energy Levels ◽  
Aluminum Arsenide ◽  
Functional Theory ◽  
Eigenvalue Gap ◽  
Rigorous Treatment ◽  
Simulation Results

ABSTRACTThe structures, energies, and energy levels of a comprehensive set of simple intrinsic point defects in aluminum arsenide are predicted using density functional theory (DFT). The calculations incorporate explicit and rigorous treatment of charged supercell boundary conditions. The predicted defect energy levels, computed as total energy differences, do not suffer from the DFT band gap problem, spanning the experimental gap despite the Kohn-Sham eigenvalue gap being much smaller than experiment. Defects in AlAs exhibit a surprising complexity—with a greater range of charge states, bistabilities, and multiple negative-U systems—that would be impossible to resolve with experiment alone. The simulation results can be used to populate defect physics models in III-V semiconductor device simulations with reliable quantities in those cases where experimental data is lacking, as in AlAs.

Defect Energy Levels in HfO2, ZrO2, La2O3 and SrTiO3

2004 ◽  
Vol 811 ◽  
Author(s):  
K Xiong ◽  
P W Peacock ◽  
J Robertson
Keyword(s):  
Band Gap ◽  
Oxygen Vacancies ◽  
Energy Levels ◽  
Density Approximation ◽  
Weighted Density ◽  
Defect Energy ◽  
High K ◽  
Screened Exchange ◽  
Weighted Density Approximation

AbstractDefect energy levels of oxygen vacancies in various high K oxides HfO2, ZrO2, La2O3 and SrTiO3 have been calculated using methods which give the correct band gap, such as the screened exchange and weighted density approximation.

scholarly journals Electron-Beam-Induced Current and Cathodoluminescence Study of Dislocations in SrTiO3

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 736
Author(s):  
Wei Yi ◽  
Jun Chen ◽  
Takashi Sekiguchi
Keyword(s):  
Electron Beam ◽  
Resistive Switching ◽  
Oxygen Vacancies ◽  
Energy Levels ◽  
Induced Current ◽  
Temperature Dependent ◽  
Recombination Activity ◽  
Defect Energy ◽  
Electron Beam Induced Current ◽  
Cathodoluminescence Study

Electron-beam-induced current (EBIC) and cathodoluminescence (CL) have been applied to investigate the electrical and optical behaviors of dislocations in SrTiO3. The electrical recombination activity and defect energy levels of dislocations have been deduced from the temperature-dependent EBIC measurement. Dislocations contributed to resistive switching were clarified by bias-dependent EBIC. The distribution of oxygen vacancies around dislocations has been obtained by CL mapping. The correlation between switching, dislocation and oxygen vacancies was discussed.

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