Ion beam-induced anisotropic plastic deformation of silicon microstructures

Amorphous silicon micropillars show anisotropic plastic shape changes upon irradiation with 30 MeV Cu ions. The transverse plastic strain rate is (2.5±0.2)×10−17 cm2/ion at 77 K, which is about one order of magnitude less than that of silica glass. In contrast, crystalline silicon pillars, irradiated under the same conditions, do not exhibit anisotropic deformation. A viscoelastic and free volume model is used to qualitatively describe the data. By irradiating partially amorphous structures a variety of silicon microshapes can be fabricated.