Electronic and optical properties of crystalline and amorphous silica from first-principles
(2013)
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- Authors
- Supervisors
- Gonze, Xavier
- Abstract
- (en) Silicon dioxide is a material of particular technological interest for its exceptional combination of properties. Indeed, both its crystalline forms and amorphous phase are widely used in many electronic and optoelectronic technologies. The amorphous form (a-SiO2) is present in many electronic devices as a gate dielectric in MOS transistors. Optical fibers are mostly made of a-SiO2 as it shows a very good optical transmission over a large range of frequencies. In all these applications, defects and impurities play an important role in the actual properties of the devices. In particular, they can cause an attenuation of the optical signal and a decrease of the bandwidth in optical fibers. An accurate understanding of these degradation processes is thus essential for the development of quality glasses as well as for improving their properties. In this work, the electronic and optical properties of pure and defect-containing silica are investigated by means of first-principles approaches. Optical spectra for the pure bulk systems are obtained with good agreement with experiment. A reverse engineering procedure is suggested to accurately determine the band gap of both the crystalline and amorphous phases, thus solving this long-standing problem. The electronic properties of hydrogen states in silica are then investigated. Their configurational, electronic and stability properties are obtained for a large statistical ensemble. Other, more technical topics are also covered in this work. The supercell and plasmon-pole approximations in GW electronic structure calculations are studied in detail in order to assess their reliability. Finally, a recently proposed exchange-correlation functional is carefully analyzed. It is shown to yield much better band gaps within density functional theory but at the expense of a less reliable valence electronic structure.
- Affiliations
Citations
Waroquiers, D. (2013). Electronic and optical properties of crystalline and amorphous silica from first-principles. https://hdl.handle.net/2078.5/163633