Hardening Characterized by a Defect Energy

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.

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Negative-U Properties for Point Defects in Silicon

MRS Proceedings ◽

10.1557/proc-2-21 ◽

1980 ◽

Vol 2 ◽

Cited By ~ 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.

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

Crystals ◽

10.3390/cryst10090736 ◽

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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Defects, Diffusion, and Dopants in Li2Ti6O13: Atomistic Simulation Study

Materials ◽

10.3390/ma12182851 ◽

2019 ◽

Vol 12 (18) ◽

pp. 2851 ◽

Cited By ~ 5

Author(s):

Navaratnarajah Kuganathan ◽

Sashikesh Ganeshalingam ◽

Alexander Chroneos

Keyword(s):

Electronic Structures ◽

Atomistic Simulation ◽

Density Functional ◽

High Capacity ◽

Ion Diffusion ◽

Functional Theory ◽

Energy Process ◽

Defect Energy ◽

Li Ion ◽

Isovalent Dopant

In this study, force field-based simulations are employed to examine the defects in Li-ion diffusion pathways together with activation energies and a solution of dopants in Li2Ti6O13. The lowest defect energy process is found to be the Li Frenkel (0.66 eV/defect), inferring that this defect process is most likely to occur. This study further identifies that cation exchange (Li–Ti) disorder is the second lowest defect energy process. Long-range diffusion of Li-ion is observed in the bc-plane with activation energy of 0.25 eV, inferring that Li ions move fast in this material. The most promising trivalent dopant at the Ti site is Co3+, which would create more Li interstitials in the lattice required for high capacity. The favorable isovalent dopant is the Ge4+ at the Ti site, which may alter the mechanical property of this material. The electronic structures of the favorable dopants are analyzed using density functional theory (DFT) calculations.

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