Virgin MgO (110) single crystals have been implanted with 30 keV ~3He~+ ions to a dose of 5X10~15 cm~-2. After implantation the samples have been annealed under air for 30 min in a tube oven. The annealing behaviour of the defects and ~3He has been monitroed by three experimental techniques: positron beam Doppler broadening, neutron depth profiling (NDP) and optical absorption in the UV to near-IR region. The observations in MgO lead to the conclusion that below 1000 deg C the vacancy like defects are stabilised by the implanted He atoms. Above this temperature He may dissociate from these small defects, alowing the formation of larger vacancy clusters. direct c 1999 Elsevier Science B.V. All rights reserved.
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