Native defects in Si-doped AlGaN grown by metalorganic vapor phase epitaxy were probed by monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and positron lifetimes were measured, and these were compared with results obtained using first-principles calculation. For Si-doped AlxGa1−xN (4 × 1017 Si/cm3), the vacancy-type defects were introduced at above x = 0.54, and this was attributed to the transition of the growth mode to the Stranski-Krastanov mechanism from the Frank-van der Merwe mechanism. For Si-doped Al0.6Ga0.4N, the vacancy concentration increased with increasing Si concentration, and the major defect species was identified as Al vacancies. A clear correlation between the suppression of cathodoluminescence and the defect concentration was obtained, suggesting the cation vacancies act as nonradiative centers in AlGaN.

Vacancy-type defects in Mg-doped GaN grown by metalorganic vapor phase epitaxy were probed using a monoenergetic positron beam. For a sample fabricated with a high H2-flow rate, before post-growth annealing the major defect species detected by positrons was identified as vacancy-clusters. Evidence suggested that other donor-type defects such as nitrogen vacancies also existed. The defects increased the Fermi level position, and enhanced the diffusion of positrons toward the surface. The annihilation of positrons at the top surface was suppressed by Mg-doping. This was attributed to the introduction of a subsurface layer (<6 nm) with a low defect concentration, where the Fermi level position was considered to decrease due to partial activation of Mg. For samples after annealing, the trapping of positrons by residual vacancy-type defects was observed, and the sample crystal quality was found to depend on that before annealing.

A pulsed, slow positron beam, with a diameter of 200 μm, was extracted into air through a thin SiN window of an atmospheric positron probe microanalyzer (PPMA), and used to measure the ortho-positronium lifetimes τ in polyvinyl alcohol and polycaprolactam sub-μm-thick films. By measuring the variation of τ as a function of relative humidity, the effect of water molecules on the hole sizes, deduced from τ, was examined for the films with consideration to the chain mobility. The results demonstrate the usefulness of the atmospheric PPMA to the in-situ characterization of nanoscopic holes in thin films under practical conditions.

Positron annihilation was used to probe vacancy-type defects in electroless deposited copper films. For as-deposited films, two different types of vacancy-type defects were found to coexist; these were identified as vacancy aggregates (V3-V4) and larger vacancy clusters (∼V10). After annealing at about 200 °C, the defects started to diffuse toward the surface and aggregate. The same tendency has been observed for sulfur only, suggesting the formation of complexes between sulfur and vacancies. The defect concentration near the Cu/barrier-metal interface was high even after annealing above 600 °C, and this was attributed to an accumulation of vacancy-impurity complexes. The observed defect reactions were attributed to suppression of the vacancy diffusion to sinks through the formation of impurity-vacancy complexes. It was shown that electroless plating has a high potential to suppress the formation of voids/hillocks caused by defect migration.

Vacancy-type defects in Ar and B gas cluster ion-implanted Si were probed by monoenergetic positron beams. The acceleration energy of the clusters ranged between 20–60 keV, and the mean cluster size was 2×103 atoms. Doppler broadening spectra of the annihilation radiation were measured, and the vacancy-rich region was found to localize at a depth of 0–13 nm. Measurements of the lifetime spectra of positrons revealed that two different defect species coexisted in the damaged region introduced by Ar gas cluster implantation, and these were identified as divacancy-type defects and large vacancy clusters filled with Ar. The formation of the vacancy clusters was attributed to extremely high temperature and its rapid transients in impact regions of Ar cluster ions. For B gas cluster ion implanted Si, the detected momentum distribution of electrons in the damaged region was broader than that in the defect free Si, suggesting that the trapping of positrons by open spaces adjacent of B clusters.