Difference in Structure and Electronic Properties of Oxygen Vacancies in α-Quartz and α-Cristobalite Phases of SiO2

Milton, Katherine; Durrant, T. R.; Freire, Teofilo Cobos; Shluger, Alexander L.

doi:10.3390/ma16041382

Cited by 5 publications

(4 citation statements)

References 102 publications

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“…However, this value depends on basis set selection: in the same ref , it was 6.08 eV already in HF/6-31G* calculations that compares, again, satisfactory to our value of 6.6 eV. The Si–Si separations obtained by SML calculation also agree with previous studies. , We omit here the discussion what values are really correct ; the level of HF/6-31G is simply not sufficient for that we only want to show that the described results are reasonable for this level and agree with previous calculations of similar quality.…”

Section: Implementation and Test Calculationssupporting

confidence: 90%

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Seamless Multilayer─A Novel Total Energy Partition Scheme for Embedded and Hybrid Calculations

Mysovsky,

Bogdanov

2023

J. Chem. Theory Comput.

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In this paper, we provide general formulation of a multilayer approach, covering both additive and subtractive quantum mechanics/molecular mechanics (QM/MM) as special cases. After that, we suggest a novel definition of QM/MM total energy based on the consideration of a system divided into three layers. In a simplified form, it is , where layers 1, 2, and 3 represent inner QM, outer QM, and classical MM regions, respectively. The novel formulation is also not limited by only QM/MM combination of methodsin fact, any computational methods can be combined in a hybrid calculation. In this paper, we call the new approach seamless multilayer. Test calculations performed for silica and boric oxide show that the new approach requires no QM/MM interface parameterization as well as no or very simple correction terms for boundary atoms. This can greatly facilitate QM/MM studies of covalent inorganic solids. However, test calculations of α-Al2O3 show that for ionic compounds, the new method requires some additional development.

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Section: Implementation and Test Calculationssupporting

confidence: 90%

“…The Si−Si separations obtained by SML calculation also agree with previous studies. 20,64 We omit here the discussion what values are really correct; the level of HF/6-31G is simply not sufficient for that we only want to show that the described results are reasonable for this level and agree with previous calculations of similar quality.…”

Section: B 2 Omentioning

confidence: 96%

Seamless Multilayer─A Novel Total Energy Partition Scheme for Embedded and Hybrid Calculations

Mysovsky,

Bogdanov

2023

J. Chem. Theory Comput.

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“…Several of these configurations have not been detected experimentally using EPR, most likely because they are metastable or require overcoming high barriers for their formation (see discussion in ref. [80]). However, there is no doubt about the existence of both neutral and positively charged oxygen vacancies in bulk crystalline and amorphous SiO 2 .…”

Section: Oxygen Deficiency In Amorphous Oxidesmentioning

confidence: 99%

On the Structure of Oxygen Deficient Amorphous Oxide Films

Strand,

Shluger

2023

Advanced Science

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Understanding defects in amorphous oxide films and heterostructures is vital to improving performance of microelectronic devices, thin‐film transistors, and electrocatalysis. However, to what extent the structure and properties of point defects in amorphous solids are similar to those in the crystalline phase are still debated. The validity of this analogy and the experimental and theoretical evidence of the effects of oxygen deficiency in amorphous oxide films are critically discussed. The authors start with the meaning and significance of defect models, such as “oxygen vacancy” in crystalline oxides, and then introduce experimental and computational methods used to study intrinsic defects in amorphous oxides and discuss their limitations and challenges. To test the validity of existing defect models, ab initio molecular dynamics is used with a non‐local density functional to model the structure and electronic properties of oxygen‐deficient amorphous alumina. Unlike some previous studies, the formation of deep defect states in the bandgap caused by the oxygen deficiency is found. Apart from atomistic structures analogous to crystal vacancies, the formation of more stable defect states characterized by the bond formation between under‐coordinated Al ions is shown. The limitations of such defect models and how they may be overcome in simulations are discussed.

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“…6), which are undesirable in all classic cases of using oxide films of silicon technology. Cristobalite has a higher density than quartz glass, and the boundaries between amorphous regions and denser crystalline regions represent voids, which can be filled both with impurities from the surface and with a diffusant in the diffusion process [23]. A necessary condition for obtaining high-quality SiO2 is the polishing of the surface of the substrates followed by chemical treatment.…”

Section: B) Defect Formation During Thermal Oxidationmentioning

confidence: 99%

Problems of Masking and Anti-Reflective SiO2 in Silicon Technology

Kukurudziak

2023

East Eur. J. Phys.

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The article examines the problems of thermal oxidation of silicon. Oxidation plays an important role in planar technology, which in turn is the basis of the technology of silicon integrated circuits, photodetectors and other solid-state electronics. During our production of silicon p-i-n photodiodes, a number of systematic types of defects and deterioration of product parameters caused by the degradation of masking or anti-reflective coatings during the manufacturing process were observed. A decrease in the insulation resistance of responsive elements in multi-element photodiodes was observed, which contributed to the increase of dark currents. A decrease in the responsivity of the products due to the degradation of the thickness or structure of the anti-reflective coating during technological operations, etc., was also revealed. It was established that the reason for the decrease in insulation resistance is the formation of inversion layers at the Si-SiO2 interface, the presence of which can be detected when measuring CV-characteristics. It was also established that chemical treatment of substrates with SiO2 in boiling acid solutions helps to reduce the thickness of the oxide. To avoid deviation of the thickness of the film from the condition of minimum reflection, it is necessary to grow a thicker layer of anti-reflective coating. It is noted that when etching the oxide during photolithography or when removing the PSG/BSG in hydrofluoric acid, it is not permissible to remove the cassette with plates from the solution for a long time, as this leads to uneven etching of the film due to the flow of the herb on the surface of the substrate. The causes of defect formation in Si and SiO2 during oxidation are given. Thus, with improper mechanical and chemical processing of the plates, cristobalite inclusions may form in the film during oxidation. Cristobalite has a higher density than quartz glass, and the boundaries between amorphous regions and denser crystalline regions represent voids, which can be filled both by impurities from the surface and by the diffusant in the diffusion process. Also, during oxidation in silicon, packing defects are often formed. Centers of defect genesis can be mechanical damage to the plate surface or growth defects.

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Difference in Structure and Electronic Properties of Oxygen Vacancies in α-Quartz and α-Cristobalite Phases of SiO2

Cited by 5 publications

References 102 publications

Seamless Multilayer─A Novel Total Energy Partition Scheme for Embedded and Hybrid Calculations

Seamless Multilayer─A Novel Total Energy Partition Scheme for Embedded and Hybrid Calculations

On the Structure of Oxygen Deficient Amorphous Oxide Films

Problems of Masking and Anti-Reflective SiO2 in Silicon Technology

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