Damage Growth in Si During Self-Ion Irradiation: a Study of Ion Effects Over an Extended Energy Range

Abstract

Damage nucleation/growth in single-crystal Si during ion irradiation is discussed. For MeV ions, the rate of growth as was well as the damage morphology are shown to vary widely along the track of the ion. This is attributed to a change in the dominant, defect-related reactions as the ion penetrates the crystal. The nature of these reactions were elucidated by studying the interaction of MeV ions with different types of defects. The defects were introduced into the Si crystal prior to high-energy irradiation by self-ion implantation at a medium energy (100 keV). Varied damage morphologies were produced by implanting different ion fluences. Electron microscopy and ion-channeling measurements, in conjunction with annealing studies, were used to characterize the damage. Subtle changes in the predamage morphology are shown to result in markedly different responses to the high-energy irradiation, ranging from complete annealing of the damage to rapid growth. These divergent responses occur over a narrow range of dose (2–3 × 10¹⁴ cm^-2) of the medium-energy ions; this range also marks a transition in the growth behavior of the damage during the predamaging implantation. A model is proposed which accounts for these observations and provides insight into ion-induced growth of amorphous layers in Si and the role of the amorphous/crystalline interface in this process.