Vacancy recovery and vacancy-hydrogen interaction in niobium and tantalum studied by positrons

Positron-lifetime measurements in electron-irradiated pure Nb and Ta show that monovacancy migration occurs at 220 and 260 K, respectively. Hydrogen impurities can be bound to vacancies, as is experimentally observed in Ta at 70 K after low-temperature α-particle irradiation. The vacancy-hydrogen complex formation shifts the vacancy migration to higher temperatures. Vacancy-hydrogen complexes retain the capability to trap positrons. Theoretical calculations performed for hydrogen and positron states at vacancies are in agreement with experimental findings.Peer reviewe

Point Defects in Undoped Semi-insulating GaAs: Correlation Between thermally Stimulated Current and Positron Annihilation Spectroscopies

Point defects and the main electron traps in undoped semi-insulating GaAs grown by vertical gradient freeze and high- and low-pressure liquid encapsulated Czochralski techniques have been studied by positron annihilation (PAS) and thermally stimulated current (TSC) spectroscopies, respectively. We find good correlations between the concentrations of the TSC traps T-2 (0.63 eV) and T-5 (0.35 eV), and the PAS identified-defects As-Ga, and V-As, respectively. A good correlation between the concentration of intrinsic accepters (V-Ga and Ga-As) measured by PAS, and the total acceptor concentration measured by infrared absorption, is also found

Point Defects in Undoped Semi-insulating GaAs: Correlation Between thermally Stimulated Current and Positron Annihilation Spectroscopies

Point defects and the main electron traps in undoped semi-insulating GaAs grown by vertical gradient freeze and high- and low-pressure liquid encapsulated Czochralski techniques have been studied by positron annihilation (PAS) and thermally stimulated current (TSC) spectroscopies, respectively. We find good correlations between the concentrations of the TSC traps T-2 (0.63 eV) and T-5 (0.35 eV), and the PAS identified-defects As-Ga, and V-As, respectively. A good correlation between the concentration of intrinsic accepters (V-Ga and Ga-As) measured by PAS, and the total acceptor concentration measured by infrared absorption, is also found