VACANCY ANNEALING IN HE AND H2 IRRADIATED MO OBSERVED BY THERMAL HELIUM DESORPTION SPECTROMETRY

Thermal helium desorption spectrometry (THDS) provides a sensitive tec hnique for measuring the concentration of vacancy type defects at low defect concentrations. This technique has been utilized to measure vac ancy annealing curves for single crystalline Mo(110) irradiated with 3 keV He, 1 keV He and 3 keV H-2 ions. In order to extract the vacancy migration energy E(V)M from the measured data, the annealing curves ha ve been analysed by using a simple diffusion model. The value of E(V)M obtained is 1.23+/-0.05 eV. In addition. an attempt has been made to examine the influence of hydrogen on the annealing behaviour of vacanc ies in Mo. It appears that hydrogen does not have any measurable influ ence on the vacancy annealing curves. The dissociation energy of hydro gen bound to vacancies in Mo is found to be less than 1.4 eV.