Defects present in ZnO nanocrystals prepared by a wet chemical method have been characterized by photoluminescence (PL) and positron annihilation spectroscopy (PAS) techniques. The as-prepared sample was heat treated at different temperatures to obtain nanocrystals in the size range of 19–39 ... (Read more)

Fluorine-vacancy (FV) complexes have been directly observed in the Si_0.94Ge_0.06 layer in a Si-SiGe-Si structure, using variable-energy positron annihilation spectroscopy (VEPAS). These complexes are linked to the significant reduction of boron diffusion in the SiGe layer via... (Read more)

We use positron annihilation spectroscopy to study 2 MeV ⁴He⁺-irradiated InN grown by molecular-beam epitaxy and GaN grown by metal-organic chemical-vapor deposition. In GaN, the Ga vacancies act as important compensating centers in the irradiated material, introduced at a... (Read more)

A laser-pump, positron-probe technique has been developed for measuring the dynamics of laser-induced paramagnetic centers in porous materials. The basis of the technique is the fact that the annihilation rate of ortho-positronium may increase in the presence of unpaired spins. By using an intense... (Read more)

Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material is shown to contain (i) vacancy clusters consisting of four to five missing atoms and (ii) Si-vacancy-related negatively charged defects. The total open volume bound to the... (Read more)

We present a detailed study of the comparative thermal evolutions of H- and D-related defects in silicon implanted with 2×10¹⁶ H or D/cm², or coimplanted with 0.25×10¹⁶ He/cm² and 0.7×10¹⁶ H/cm², in both orders.... (Read more)

We have measured positron lifetime and Doppler broadening in highly As-doped silicon containing thermally generated V-As₃ defect complexes (vacancy is surrounded by three arsenic atoms). We observe positron detrapping from the V-As₃ defect complex and determine... (Read more)

The migration of monovacancies (V⁰) and self-interstitials (I) has been observed in ion-implanted low-doped float-zone silicon by variable-energy positron annihilation spectroscopy. V⁰ and I were created by the in situ implantation of ~20 keV... (Read more)

The effects of nitridation on open volumes in thin HfSiO_x films fabricated by metal-organic chemical vapor deposition were studied using monoenergetic positron beams. It was found that positrons were annihilated from the trapped state by open volumes that exist intrinsically in... (Read more)

Defect centers generated in crystalline silicon by MeV Si implants have been investigated by a combination of photoluminescence, variable-energy positron annihilation measurements, depth profiling by etching, annealing studies, and the dependence on impurities. The broad 935 meV photoluminescence... (Read more)

The impact of TiN deposition on thin HfO₂ films formed on Si substrates was studied using x-ray photoelectron spectroscopy and a monoenergetic positron beam. For the predeposition sample, the positrons implanted into Si were found to diffuse toward the HfO₂/Si interface under... (Read more)

Vacancies are known often to be the dominant type of point defects in perovskite oxides, but their presence can rarely be directly determined. Positron annihilation methods have unique sensitivity to vacancy-related defects and the variable energy positron beam (VEPB) techniques allow near-surface... (Read more)

Vacancy-impurity complexes in polycrystalline Si (poly-Si) used as a gate electrode of the metal-oxide-semiconductor field-effect transistor (MOSFET) were probed using monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and the positron lifetimes were measured for... (Read more)

The impact of nitridation on open volumes in thin HfSiO_x films fabricated on Si substrates by atomic layer deposition was studied using monoenergetic positron beams. For HfSiO_x, positrons were found to annihilate from the trapped state due to open volumes which... (Read more)

Systematic slow positron implantation spectroscopy (SPIS) and atomic force microscopy studies of various 6H-SiC samples are presented to clarify the role of conductivity type, crystal quality, ion implantation (B⁺,Al⁺, and N⁺), and annealing (1.650 °C) in... (Read more)

High-quality single crystals of ZnO in the as-grown and N⁺ ion-implanted states have been investigated using a combination of three experimental techniques—namely, positron lifetime/slow positron implantation spectroscopy accompanied by theoretical calculations of the positron... (Read more)

The structure of the SiO₂/4H-SiC interface produced by dry oxidation has been studied using positron annihilation spectroscopy using energy-variable slow positron beams. Based on the Doppler broadening shape and wing parameter (S-W) correlation, the interface layer was... (Read more)

Two-dimensional angular correlation of annihilation radiation (2D-ACAR) and coincidence Doppler broadening (CDB) of annihilation radiation measurements have been performed on electron-irradiated n-type 3C-SiC in which isolated silicon vacancies are responsible for positron trapping.... (Read more)

Electron-positron momentum distributions associated with vacancy defects in 6H-SiC after irradiation with 2-MeV electrons and annealing at 1000 °C have been studied using angular correlation of annihilation radiation measurements. It was confirmed that the above vacancy defects have... (Read more)

We show direct evidence, obtained by positron annihilation spectroscopy, for the complexing of fluorine with vacancies in silicon. Both float zone and Czochralski silicon wafers were implanted with 30 keV fluorine ions to a fluence of 2×10¹⁴ ions/cm², and studied in the... (Read more)

Using positron annihilation measurements we observed the formation of thermal vacancies in highly As and P doped Si. The vacancies start to form at temperatures as low as 650 K and are mainly undecorated at high temperatures. Upon cooling the vacancies form stable vacancy-impurity complexes such as... (Read more)

The effect of vacancies on the behavior of F in crystalline Si has been elucidated experimentally for the first time. With positron annihilation spectroscopy and secondary ion mass spectroscopy, we find that F retards recombination between vacancies (V) and interstitials (I) because V and I trap F to form complexes. F diffuses in the V-rich region via a vacancy mechanism with an activation energy of 2.12±0.08 eV. After a long annealing time at 700ºC, F precipitates have been observed by cross-section transmission electron microscopy which are developed from the V-type defects around the implantation range and the I-type defects at the end of range. (Read more)

We apply positron annihilation spectroscopy to identify V_N–Mg_Ga complexes as native defects in Mg-doped GaN. These defects dissociate in postgrowth annealings at 500–800 °C. We conclude that V_N–Mg_Ga complexes contribute to... (Read more)

The identification of atomic defects in solids is of pivotal interest for understanding atomistic processes and solid state properties. Here we report on the exemplary identification of vacancies on each of the two sublattices of SiC by making use of (i)?electron irradiation, (ii)?measurements of... (Read more)

Annealing behavior of vacancies and the Z_1/2 levels in n-type 4H–SiC epilayers after 2 MeV electron irradiation has been studied using positron annihilation and deep-level transient spectroscopy. Isochronal annealing studies indicate that silicon vacancy-related defects... (Read more)

The depth distributions of oxygen-related defects in separation-by-implanted oxygen wafers were determined from measurements of Doppler broadening spectra of the annihilation radiation. Vacany–oxygen complexes were introduced by implanting 180-keV oxygen at (2–6)×10¹⁷ ... (Read more)

The annealing behavior of defects in n-type 6H SiC epilayers irradiated with 2 MeV electrons have been studied using positron annihilation and deep level transient spectroscopy. Vacancy-type defects are annealed at 500–700 °C and 1200–1400 °C. From the analysis of... (Read more)

n-type 6H silicon carbide has been studied using positron lifetime spectroscopy with isochronal annealing temperatures of 400, 650, 900, 1200, and 1400 ?C. In the as-grown sample, we have identified the V_Si vacancy, the V_CV_Si divacancy, and probably the V_C... (Read more)

Isochronal annealing investigations in electron-irradiated 6H-SiC were correlated with temperature-dependent measurements of positron lifetime. It turned out that the positron trapping at temperatures up to 300 K was dominated by the trapping in shallow positron traps. These defects were already... (Read more)

Positron lifetime and electron spin resonance (ESR) measurements were performed for 1-MeV electronirradiated cubic silicon carbide (3C-SiC). From a comparison of the annealing behaviors of positron lifetime and ESR signal, we identified the annihilation of positrons localized at single-negative silicon vacancies. The positron lifetime at silicon vacancies was first determined experimentally to be 188|±|4 ps. This value agrees well with the theoretical positron lifetime for silicon vacancies [G. Brauer et al. Phys. Rev. B 54, 2512 (1996)]. The trapping coefficient of singlenegative silicon vacancies was also derived. (Read more)

Positron-lifetime and Doppler-broadening spectroscopies were used to investigate vacancies formed by 2.2- and 10-MeV electrons. Carbon vacancies yield a positron lifetime of 160 ps, only 15 ps longer than the bulk lifetime, and the Doppler-broadening S parameter is very close to that for the bulk.... (Read more)