UCL logo

UCL Discovery

UCL home » Library Services » Electronic resources » UCL Discovery

First-principles studies of surface defects of model metal-oxide semiconductors

Beglitis, N.; (2011) First-principles studies of surface defects of model metal-oxide semiconductors. Doctoral thesis , UCL (University College London). Green open access


Download (14MB)


In this thesis, three di�fferent model metal-oxide semiconductor systems will be discussed. First, the impact of hydroxyl vacancies, OHvac, on the geometry, electronic structure, and mechanical properties of single-walled aluminosilicate, (Al2SiO7H4)N, and aluminogermanate, (Al2GeO7H4)36, nanotubes is investigated. It is found that, with the exception of one OHvac localised on the outer wall of the (Al2GeO7H4)36 tube, these defects induce occupied and empty states in the band gap. Those states are found to be highly localised both in energy and in real space. Different magnetisation states are also found, depending on both the chemical composition and the specifi�c side with respect to the tube cavity. The focus of the thesis then shifts to one of the most important and well-studied metaloxide surfaces, the rutile TiO2(110) surface. The reactivity of the surface is revisited, in view of the discrepancy between theory and experiment on the interaction between molecular oxygen and surface hydroxyls. This discrepancy is resolved by proposing that excess charge, associated with the oxygen vacancy and originating from Ti interstitials, is present on the surface. This surface charge opens new reaction channels not theoretically possible otherwise. The study utilises hybrid Density Functional Theory (DFT) calculations and Scanning Tunneling Microscopy (STM) simulations to provide evidence for the proposed surface charging. The last part of the thesis focuses on another surface of TiO2, the (011) surface. TiO2(011) has recently attracted attention due owing to its reported high photocatalytic activity. Several proposed structures of the surface are inconsistent with each other. Recent developments, based on Surface X-Ray Diffraction (SXRD) data and DFT simulations, now agree on a new structure. In this part a review of the various structures is provided and further evidence is given on the validity of the new proposal by providing further insight on the appearance of the surface on the STM.

Type: Thesis (Doctoral)
Title: First-principles studies of surface defects of model metal-oxide semiconductors
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: http://discovery.ucl.ac.uk/id/eprint/1324515
Downloads since deposit
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item