It was found that, in H-containing float-zone material which had been irradiated with reactor neutrons to a dose of 1.2 x 1018/cm2, about 20% of the neutron-induced V-type defects were decorated with H atoms. A very striking so-called false annealing of V-type defects at 200C was found, due to H passivation. At temperatures between ambient and 200C, the annealing out of V2 defects became slower, and the apparent concentration of secondary V2 defects reached its maximum value at lower temperatures because some of the V2 defects were also decorated with H. The maximum concentration could be independent of H, and be related only to the neutron dose or to the concentration of V2 defects in disordered regions. It was observed that H promoted the annealing out of V-type and secondary V2 defects, and impeded the formation of multi-vacancy clusters. At 600C, the reappearance of V-type defects was attributed to the breaking of Si-H bonds in neutron-irradiated samples which contained H and to the so-called 600C acceptor in the case of neutron-irradiated samples which had been grown in an Ar atmosphere.

X.T.Meng: Solid State Communications, 1994, 90[7], 455-60