Unveiling the identity, spatial configuration, and microscopic structure of point defects is one of the key challenges in materials science. Here, we demonstrate that quantitative scanning transmission electron microscopy (STEM) can be used to directly observe Sr vacancies in SrTiO3 and to determine the atom column relaxations around them. By combining recent advances in quantitative STEM, incl...

This paper estimates a model of two-sided search using micro-level data for a well-defined labour market. It examines the assumption of random matching and contrasts it with the stock-flow (or non-random) matching model of Coles and collaborators. Given a dataset of contacts, matches, and complete labour-market histories for both sides of the market, we estimate hazard functions for both (unemp...

The microscopic mechanism leading to stabilization of cubic and tetragonal forms of zirconia (ZrO2) is analyzed by means of a self-consistent tight-binding model. Using this model, energies and structures of zirconia containing different vacancy concentrations are calculated, equivalent in concentration to the charge compensating vacancies associated with dissolved yttria (Y2O3) in the tetragon...

A novel oxygen vacancy assisted transition metal (TM) diffusion mechanism is proposed for the first time to explain the near-surface phase transformation in lithium excess transition metal layered oxides. Oxygen vacancies and TM migration have been observed at nm scale spatial resolution by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy. Formation of (dilute) ox...

Ab initio density functional theory and ballistic transport theory are applied to the calculation of tunneling current through ultra-thin SiO2 gate dielectrics. The Si/SiO2/Si model interface has been constructed by orienting a crystalline SiO2 (β−cristobalite) slab such that the misfit with Si (001) was minimized and no dangling bonds appear at the interface. The structure was then sandwiched ...

A possible mechanism for shock-induced failure in aluminium involves atomic vacancies diffusing through the crystal lattice and agglomerating to form voids, which continue to grow, ultimately resulting in ductile fracture. We employ orbital-free density functional theory, a linear-scaling first-principles quantum mechanics method, to study vacancy formation, diffusion, and aggregation in alumin...

Oxygen vacancies have been considered as the origin of threshold voltage instability under negative bias illumination stress in amorphous oxide thin film transistors. Here we report the results of first-principles molecular dynamics simulations for the drift motion of oxygen vacancies. We show that oxygen vacancies, which are initially ionized by trapping photoexcited hole carriers, can easily ...

The influence of local magnetic moment formation around three kinds of vacancies on the electron conduction through metallic single-wall carbon nanotubes is studied by use of the Landauer formalism within the coherent regime. The method is based on the single-band tight-binding Hamiltonian, a surface Green function calculation, and the mean-field Hubbard model. The numerical results show that t...

We have applied a low-energy positron beam and secondary ion mass spectrometry to study defects in homoepitaxial and heteroepitaxial GaN layers. Positron experiments reveal high concentrations of Ga vacancies in nominally undoped n-type GaN, where the conductivity is due to unintentional oxygen incorporation. Ga vacancies are observed in both homoepitaxial and heteroepitaxial layers, indicating...

Reduction behaviors, oxygen vacancies and hydroxyl groups play decisive roles in the surface chemistry and catalysis of oxides. Employing isothermal H2 reduction we simultaneously reduced CeO2 nanocrystals with different morphologies, created oxygen vacancies and produced hydroxyl groups. The morphology of CeO2 nanocrystals was observed to strongly affect the reduction process and the resultant...