Tailoring the spring constant of Si nanorod structures using swift heavy ion irradiation

This study reports a post-deposition technique of engineering the mechanical properties of cantilever-like silicon nanorods by using swift heavy ion irradiation. Slanted silicon nanorods grown by glancing angle deposition technique on a patterned Si(1 0 0) substrate are irradiated by 100 MeV Ag+8 ions at a fluence of 1014 ions cm−2. The average spring constant (k) of the nanorods determined by force–distance spectroscopy reduces to 65.6 ± 20.8 Nm−1 post-irradiation as compared to 174.2 ± 26.5 Nm−1 for pristine nanorods. Scanning electron micrographs show bending of the Si nanorods after irradiation. Micro-Raman and high-resolution transmission electron microscope studies on pristine and irradiated Si nanorods confirm the transformation of nanocrystalline regions present in pristine nanorods to amorphous phase on irradiation. This structural transformation and bending of the nanorods are responsible for the observed changes in the mechanical properties post-irradiation. The technique offers a simpler possibility of tailoring mechanical properties of nanostructures post-deposition by ion irradiation.