Diffusion and aggregation of oxygen vacancies in amorphous silica

Journal of Physics. Condensed Matter : an Institute of Physics Journal
Manveer S MundeAlexander L Shluger

Abstract

Using density functional theory (DFT) calculations, we investigated oxygen vacancy diffusion and aggregation in relation to dielectric breakdown in amorphous silicon dioxide (a-SiO2). Our calculations indicate the existence of favourable sites for the formation of vacancy dimers and trimers in the amorphous network with maximum binding energies of approximately 0.13 eV and 0.18 eV, respectively. However, an average energy barrier height for neutral vacancy diffusion is found to be about 4.6 eV, rendering this process unfeasible. At Fermi level positions above 6.4 eV with respect to the top of the valence band, oxygen vacancies can trap up to two extra electrons. Average barriers for the diffusion of negative and double negatively charged vacancies are found to be 2.7 eV and 2.0 eV, respectively. These barriers are higher than or comparable to thermal ionization energies of extra electrons from oxygen vacancies into the conduction band of a-SiO2. In addition, we discuss the competing pathways for electron trapping in oxygen deficient a-SiO2 caused by the existence of intrinsic electron traps and oxygen vacancies. These results provide new insights into the role of oxygen vacancies in degradation and dielectric breakdown in amorp...Continue Reading

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Citations

Jun 30, 2018·Advanced Materials·Adnan MehonicAnthony J Kenyon
Feb 23, 2019·Frontiers in Chemistry·Andi CukoMonica Calatayud
Sep 19, 2019·ACS Applied Materials & Interfaces·Jonathon CottomAlexander L Shluger
Apr 25, 2019·The Journal of Physical Chemistry. a·Nadire NayirSakir Erkoc

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