Spatial effects in the 800Â keV 3He implantation in W followed by isochronal annealing at 900Â K

The effect of fluence on the depth distribution of vacancy clusters in the track region of room temperature 800 keV 3He atom implanted tungsten further annealed up to 900 K has been investigated using an Object Kinetic Monte Carlo (OKMC) approach. The results show that the width and the position of the maximum size of the depth distribution strongly depend on the implantation fluence. For the high implantation fluence, the vacancy clusters are the largest in the first 100 nm close to the surface, whereas, for the low implantation fluence, the distribution is more uniform in size between 100 and 300 nm from the surface. The vacancy clusters are always smaller very close to the surface, and this whatever the fluence. The trends observed are in good agreement with the experimental Positron Annihilation Spectroscopy (PAS) results.