DAMAGE PRODUCTION IN SI BY MEV CARBON CLUSTER IRRADIATION

Monocrystalline silicon has been irradiated by MeV carbon clusters (C-n, n=1,2,3,4) with fluences up to 3 x 10(16) C atoms per cm(2). The produced defect concentration in a depth between 100 and 200 nm below the sample surface has been measured by channeling RBS. For energies above approximately 0.5 MeV per carbon atom the polyatomic particles produce less defects per incident atom than single C ions of the same velocity This effect increases with energy and cluster size. The largest reduction of the produced defects per atom measured so far is 40% for the C-2, molecule at an energy of 4 MeV per C atom. A possible explanation for the effect is an increase in the defect annealing rate caused by the larger primary point defect concentration and the enhanced deposited energy density along a particle track.