Amorphization of Silicon by Ion Irradiation: The Role of the Divacancy

Abstract

ABSTRACTFixed fluence ion irradiation of silicon is shown to produce either defected crystal or amorphous silicon depending on the ion flux employed. The amorphous threshold flux, defined as the minimum flux required to generate a continuous amorphous layer for a fixed fluence irradiation, is measured as a function of irradiation temperature. This critical flux for amorphization is shown to satisfy an Arrhenius expression with a unique activation energy of ∼1.2eV, which corresponds to the migration/dissociation energy of the silicon divacancy. These observations lead to the conclusion that the stability of the silicon divacancy controls the competition between defect production and dynamic defect annealing, and hence the crystalline to amorphous phase transformation.