RBS-channeling studies on damage production by MeV ion implantation in Si(111) wafers

Abstract

Little experimental data are available concerning the accumulation of damage in MeV ion irradiated crystalline samples, as most of the work has been performed at energies below 1 MeV. In the present work, Si(111) wafers have been irradiated at room temperature with 2 MeV Cu and Ag ions, and 2.5 MeV Au ions at fluences between 5×10 12 and 1.5×10 15 ions cm −2. The damage depth profiles were extracted from RBS-channeling spectra using the two-beam model. Two different approaches were used for determining the dechanneled fraction of the beam χ D( z), and a comparison was made between them. The results show that the structural damage accumulation strongly depends on the ion mass, and increases with the ion fluence, and that it is a non-linear phenomenon. The mechanisms responsible for the damage growth and amorphization of Si samples is well described by the so-called nucleation and growth model, and our results indicate that mainly a three-dimensional growth mechanism takes place when irradiating with Ag and Au ions, and a two-dimensional one occurs for Cu implantation.