Influence of the finite-size effect on the cluster ion emission of silicon nanostructures

The finite-size effect increasing the emission of polyatomic cluster ions from silicon nanostructures as compared to a macroscopic sample has been studied. This study has been performed for the first time in periodic structures with $10$- and $50$-nm-wide combs fabricated by electron beam lithography with subsequent plasma chemical etching. It has been shown that the yield of polyatomic cluster ions from structures with the comb whose effective width is comparable with the projective range of a bombarding bismuth ion in silicon is much higher than the yield from macroscopic samples, e.g., by more than a factor of $5$ for $^{28}$Si$^-_{10}$ ($m/z=280$). This effect has been explained by a partial limitation of dissipation channels for the energy released by the bombarding ion in the volume of the structure, which stimulates a more efficient development of nonlinear collision cascades in such a volume and, as a result, increases the yield of polyatomic cluster ions.