We have used positron annihilation spectroscopy to study vacancy defects in ZnO single crystals grown by various methods from both commercial and academic sources. The combination of positron lifetime and Doppler broadening techniques with theoretical calculations provides the means to deduce both the identities and the concentrations of the vacancies. The annihilation characteristics of the Zn...

: We present phonon thermal conductance calculations for silicon nanowires (SiNWs) with diameters ranging from 1 to 5 nm with and without vacancy defects by the non-equilibrium Green's function technique using the interatomic Tersoff-Brenner potentials. For the comparison, we also present phonon thermal conductance calculations for diamond nanowires. For two types of vacancy defects in the SiNW...

Motivated by recent developments in solid electrolytes based on lithium phosphorous oxynitride (LiPON) materials, we carried out computer simulations in order to develop an understanding of the detailed mechanisms of ionic transport. Starting with crystalline Li3PO4, we investigated some possible structures of isolated defects associated with extrinsic Li ion vacancies and interstitials. In par...

Cuprous oxide (Cu2O) is an attractive material for solar energy applications, but its photoconductivity is limited by minority carrier recombination caused by native defect trap states. We examine the creation of trap states by cation vacancies, using first principles calculations based on density functional theory (DFT) to analyze the electronic structure and calculate formation energies. With...

In this work, we have systematically studied the role of point defects in recombination time monolayer MoS$_2$ using time-dependent ab initio non-adiabatic molecular dynamics simulations. Various types defects, such as S vacancy, interstitial, Mo vacancy and interstitial been considered. We show that strongly accelerate electron-hole recombination, especially atoms do by 3 orders magnitude high...

Arsenic vacancies in LaFeAsO-derived superconductors are nominally non-magnetic defects. However, we find from a microscopic theory in terms of an appropriately modified Anderson-Wolff model that in their vicinity local magnetic moments form. They can arise because removing an arsenic atom breaks four strong, covalent bonds with the neighboring iron atoms. The moments emerging around an arsenic...

Positron lif etimes and Do ppler broadening of the annihi l atio n line mea surements were perf ormed to study the vacancy typ e defects in polycrystallin e GeT e and (GeT e) ( 1 À x ) (A gBiT e2 ) x ( = 0 0 0 3 0 05 0 1 0 15 0 2, and 1) solid solutio ns. The values of lif etimes obtained are explaine d as due to positron and p ositronium saturated trapping at vacancies and vacancy clusters. T ...

Nanodiamonds (NDs) containing silicon vacancy (SiV) defects were evaluated as a potential biomarker for the labeling and fluorescent imaging of neural precursor cells (NPCs). SiV-containing NDs were synthesized using chemical vapor deposition and silicon ion implantation. Spectrally, SiV-containing NDs exhibited extremely stable fluorescence and narrow bandwidth emission with an excellent signa...

We report on 18O tracer diffusion experiments and model calculations for the study of cation vacancy migration in oxide crystals. The model takes advantage of the electrostatic coupling forces between anion and cation defects that allow the evolution of the cation vacancy profile to be observed by anion tracer experiments. Applied to SrTiO3, the ambipolar diffusion of strontium vacancies with H...

Isolated point defects possessing a high spin ground state and below-band-gap excitation may play a key role in realizing solid state quantum bits in semiconductors which are the basic building blocks of quantum computers. The silicon vacancy in silicon carbide provides these features, making it a feasible candidate in this special and emerging field of science. However, the exact nature of the...