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

Fluorine in Silicon - Diffusion, Trapping and Precipitation. X.D.Pi, C.P.Burrows, P.G.Coleman: Physical Review Letters, 2003, 90[15], 155901 (4pp)