First-principles study of defects in amorphous-SiO2/Si interfaces
| Autor: | Pei Li, Xu Zuo, Pei Yao, Yu Song, Zehua Chen, Fu-Jie Zhang, Jianwei Wang |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Fermi contact interaction Band gap Fermi level Dangling bond General Physics and Astronomy 02 engineering and technology Surfaces and Interfaces General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Molecular physics 0104 chemical sciences Surfaces Coatings and Films symbols.namesake Vacancy defect Density of states symbols Charge carrier 0210 nano-technology Hyperfine structure |
| Zdroj: | Applied Surface Science. 483:231-240 |
| ISSN: | 0169-4332 |
| Popis: | Defects in amorphous-SiO2/Si (a-SiO2/Si) interfaces influence greatly the performance and reliability of Si-based devices. The major interfacial defects that exhibit electronic activity are silicon dangling bonds (so-called Pb defects), which can trap charge carriers and contribute to interfacial charge build-up. In this study, the Pb0 and Pb1 defects at the most technically important a-SiO2/Si(100) interface are investigated quantitatively by using first-principles calculations with realistic interfacial models. Atomistic models of the interface are generated by classical molecular dynamics simulations of Si oxidation with a-SiO2 followed by first-principles structure optimization, and they can reproduce the experimental interfacial properties of the short-range structure parameters, Si oxidation state distribution, and band gap transition. The Pb0 and Pb1 defects are modeled atomistically within the interfacial models, and their g-values and hyperfine parameters are calculated quantitatively by the GIPAW (gauge including projector augmented waves) method. The Fermi contact and hyperfine axis (hf axis) calculated with the Si vacancy model for the Pb0 defect agree well with those obtained experimentally, and the hf axis is coincident with the dangling bond direction determined from the calculated g-tensor and spin density. The Fermi contact and hf axis are calculated for the Pb1 defect with three different models, namely dimer, bridge, and asymmetrically oxidized dimer (AOD), of which the AOD model leads to calculated results that agree well with the experimental ones. However, the AOD model is found to be sensitive to the local structure distortion associated with the softness of the oxygen bridge. What is known as the half AOD is then introduced by deoxidizing one of the two oxygen bridges of the AOD; this may serve as another atomistic model of the Pb1 defect according to the good agreement between the calculated Fermi contact, g-values, and hf axis and the experimental ones. The electronic structures are calculated with the atomistic defect models and show that both defects induce (i) two spin-asymmetric midgap levels in the Si band gap in the neutral state and (ii) spin-symmetric levels in the charged states. The charge transition levels of the defects are calculated with a correction method that is specific to surface/interfacial charge defects, and the calculated levels agree semi-quantitatively with those determined experimentally. The calculated +/0 and 0/− levels are in the Si band gap, with the 0/− level energy being higher than the +/0 one. This implies that both Pb0 and Pb1 defects can trap holes or electrons depending on the position of the Fermi level. |
| Databáze: | OpenAIRE |
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