Collision Cascades, Ionization, Spikes And Energy Transfer

Mechanical Property Characterisation of Crystalline, Ion Implantation Amorphised and Annealed Relaxed Silicon with Spherical Indenters

Silicon single crystals have been ion implanted with Si ions at various energies and doses sufficient to achieve amorphisation to a depth of more than 1μm. This surface was subsequently annealed at 450°C for 30 minutes in vacuum to relax the implanted amorphous silicon. Mechanical properties of the different materials (crystalline, amorphous and annealed) were measured using a nominally 10 μm radius diamond tipped indenter and two indenting procedures; continuous loading and load partial-unloading. The crystalline material exhibited similar force-displacement behaviour to that observed by Weppelmann et al. [1] including a critical pressure to induce deformation on loading and a "pop-out" event during unloading. The amorphous and annealed materials showed a greater degree of plastic deformation but did not exhibit "pop-out" behaviour at lower loads (200 mN). The results are analysed to determine the difference of mean pressure with depth of penetration for all the materials. The onset of ductility was 5.5 to 6 GPa for the amorphous material and 10.9 GPa for the crystalline material. The depth dependence of hardness for the amorphous and annealed material showed substantial evidence of work hardening whereas the crystalline material did not.