OPTICAL STUDY OF MEV ENERGY HEAVY-ION-INDUCED EFFECTS IN CRYSTALLINE GERMANIUM AND SILICON

An optical study of Ni-ion (60 and 75 MeV) bombarded polished single crystals of Ge ([111], sb-doped, 1 Omega cm) and Si ([111], intrinsic) at room temperature with fluence ranging from 1 X 10(13) to 1 X 10(15) ions/cm(2) has been carried out in the spectral regions of the fundamental optical absorption edge and interband transition. The damage inflicted by the MeV energy ion on the surface and deep inside the bulk of the semiconductors has been monitored by determining the dose dependence of optical constants alpha, R and n in the spectral range 200-2500 nm. Analysis of the results reveals that electronic energy loss arising out of the inelastic ionising collisions of swift heavy ions, in addition to the nuclear energy loss, influence the surface and the bulk properties of the bombarded semiconductors. Formation of divacancies in the bombarded Si is supported by the appearance of an absorption band at around 0.7 eV. The surface effects of ion-implantation at MeV energy are quite different from those at keV energy.