Study of crystal damage by ion implantation using micro RBS/Channeling

The combination of microbeam implantation and in-situ micro RBS/Channeling analysis in the Rossendorf nuclear microprobe facility enables crystal damage studies with high current densities not achievable in standard ion implantation experiments. Si(100) samples were implanted with 600 keV Si+ ions and a fluence of 1 x 1016 Si/cm². Using a beam spot of 200 µm x 200 µm current densities from 4 to 120 µA/cm² were obtained. The substrate temperature was varied between RT and 265 °C. The implanted regions were subsequently analysed by micro RBS/Channeling with a 3 MeV He+ beam having a spot size of 50 µm x 50 µm.
Crystal damage up to amorphisation was obtained in dependence on the substrate temperature. Above a critical temperature TC no amorphisation occurs. TC was determined for each series of samples implanted with the same ion current density j. It was found that the empirical Arrhenius relation j ~ exp(- Em/ kTC), known from standard implantation experiments, is also valid at high current densities. The observed Arrhenius law can be derived from a model of epitaxial crystallisation stimulated by defect diffusion.