We apply a combination of positron annihilation spectroscopy and scanning tunneling microscopy to show that thermally generated P vacancies diffuse from the InP surface toward the bulk. The defect observed in the bulk can be identified as a complex consisting of a P vacancy and a Zn impurity. We infer that this pair is formed when the diffusing positive P vacancy is trapped at the Zn dopant. A ...

We have studied the role of defects on the magnetic properties of carbon materials using first-principles density functional methods. We show that, while the total magnetization decreases both for diamond and graphite with increase in vacancy density, the magnetization decreases more rapidly for graphitic structures. The presence of nitrogen nearby a vacancy is shown to produce larger macroscop...

The correlation between thermal vacancy characteristics and D03 ordering in ball-milled nanocrystalline (Fe3Si)95Nb5 was studied by combined measurements of x-ray diffraction and positron annihilation. Structural stabilization due to grain boundary segregation of Nb enables high-temperature positron lifetime measurements up to 1023 K from which vacancy formation parameters identical to those in...

We report the realization of the optically induced inverse population of the ground-state spin sublevels of the silicon vacancies (V(Si)) in silicon carbide (SiC) at room temperature. The data show that the probed silicon vacancy spin ensemble can be prepared in a coherent superposition of the spin states. Rabi nutations persist for more than 80 μs. Two opposite schemes of the optical alignment...

Electrical properties of semiconductor materials are greatly influenced by point defects such as vacancies and interstitials. These defects are common and form during the growth and processing of the material. Positron annihilation spectroscopy is a method suitable for detecting and studying vacancy-type lattice defects. In this work, the formation, properties, and annealing of vacancy defects ...

With particular focus on bulk heterojunction solar cells incorporating ZnO nanorods, we study how different annealing environments (air or Zn environment) and temperatures impact on the photoluminescence response. Our work gives new insight into the complex defect landscape in ZnO, and it also shows how the different defect types can be manipulated. We have determined the emission wavelengths f...

Perturbed angular correlation of gamma rays was applied to determine properties of equilibrium defects in B2 NiAl near the stoichiometric composition. Point defects were detected through quadrupole interactions they induce at In probe atoms on the Al sublattice. Well-resolved signals were observed for probe atoms having zero, one or two Ni-vacancies (VNi) in the first neighbor shell. The fracti...

The presence of defects in a regular structure of graphene and carbon nanotubes (CNTs) can significantly influence their mechanical properties. In this work, the effect of an absence of a carbon atom (vacancy defect) on the strength of a graphene sheet and a single walled carbon nanotube (SWCNT) is studied using quasi static molecular dynamics (QSMD) simulations. Results show that a graphene sh...

We discuss how electronic-structure calculations can be used to identify the dominant point defects that control the growth and dissolution of the oxide barrier layer formed if a metal comes into contact with a corrosive environment. Using the example of the Zn/ZnO/H(2)O interface we develop and apply a theoretical approach that is firmly based on ab initio computed defect formation energies an...

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...