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Currently, diamonds are widely used in science and technology. However, the properties of diamonds due to their defects are not fully understood. In addition to optical methods, positron annihilation spectroscopy (PAS) can be successfully used to study defects in diamonds. Positrons are capable of detecting vacancies, and small and large clusters of vacancies induced by irradiation, by providing information about their size, concentration, and chemical environment. By mapping in the infrared (IR) range, it is possible to consider the admixture composition of the main inclusions of the whole plate. This article presents the results of a study of defects in synthetic diamond plates, one of which was irradiated by electrons. It presents data about the distribution of the defect concentration obtained by Infrared spectroscopy. PAS with a monochromatic positron beam can be used as a non-destructive technique of detecting defects (vacancy) distribution over the depth of diamond plates. [ABSTRACT FROM AUTHOR]

The thermal evolution of defects inside and beyond the implantation layer in Si wafer exposed to the irradiation with 25 keV C+, N+ and Ar+ ions with different doses has been investigated by positron beam measurements. Two types of defects were detected: the small cavities and divacancies in the implanted layer which thickness corresponding to the projectile range. Cavities were only present for dose 2*1016 and were not observed for 2*1014 and 2*1015 ions/cm2. For the dose of 2*1016 ions/cm2 the defects were detected also beyond the implantation layer indicating the presence of the long range effect. Obtained results indicate on influence of ion type and dose on defect distribution and its thermal evolution beyond the implanted layer. The recovery process was similar for Ar+ and N+ but differ for C+ ion implantation. [ABSTRACT FROM AUTHOR]

Abstract Results of positron annihilation spectroscopy studies of pure gold samples irradiated with various doses of Xe26+ have been reported. The conventional positron lifetime measurements and positron beam tests were performed. Increase of positron lifetime in irradiated samples up to ca. 170 ps is interpreted as the existence of stacking fault tetrahedras in all studied samples. The damaged zone determined in etching experiment equals 9 μm and it is in a good agreement with theoretical results. The long range effect was not found. The positron beam studies provide information about the increase of defect concentration with the growing number of displacements per atom achieved during irradiation. Highlights • Radiation-induced defects are visible in all PAS characteristics. • Stacking fault tetrahedras were recognized. • Existing of long-range effect in gold is not observed. • Defects concentration increases with the number of displacements per atom in near-surface region. [ABSTRACT FROM AUTHOR]

Abstract The paper reports studies of pure, polycrystalline iron samples exposed to proton implantation with energies of 73 keV and 173 keV and doses of 3 × 1015, 1016 and 3 × 1016 cm−2. Additionally, two samples were exposed to multiple implantation with different energies and fluencies. Variable energy positron beam (VEP) was applied to the detection of irradiation-induced defects and their distribution. In turn, elastic recoil detection (ERD) method was used to estimate hydrogen concentration and its range. Analysis of VEP results was performed with VEPFIT code. The strong reduction of positron diffusion lengths in the implanted layers point out the presence of defects with high concentration. The thicknesses of these layers are in good agreement with hydrogen range evaluated by ERD. However, the presence of defects with lower concentration behind implanted zone was also detected when the free fitting was performed. The long range effect cannot be excluded. [ABSTRACT FROM AUTHOR]

Vacancy‐type defects in Mg‐implanted GaN with and without hydrogen (H) implantation are probed by using monoenergetic positron beams. Mg+ and H+ ions are implanted into GaN(0001¯) to obtain 0.1 and 0.7‐µm‐deep box profiles with Mg and H concentrations of 1 × 1019 and 2 × 1020 cm−3, respectively. For the as‐implanted samples, the major defect species is determined to be Ga‐vacancy (VGa) related defects such as VGa, divacancy (VGaVN), and their complexes with impurities. For Mg‐implanted samples, an agglomeration of vacancies starts at 800 °C annealing, leading to the formation of vacancy clusters such as (VGaVN)3. For the samples annealed above 1000 °C, the trapping rate of positrons by vacancies is increased by illumination of a He–Cd laser. This is attributed to the capture of photon‐excited electrons by the defects and their charge transition. For Mg‐ and H‐implanted samples, the hydrogenation of vacancy‐type defects starts after 800 °C annealing. Comparing with the annealing behavior of defects for the samples without H‐implantation, the clustering of vacancy‐type defects is suppressed, which can be attributed to the interaction between Mg, H, and vacancies. [ABSTRACT FROM AUTHOR]