Nanofabrication of self-organized periodic ripples by ion beam sputtering

Ion beam sputtering can induce the formation of regular self-assembled surface nanostructures on different materials. Several experimental variables, such as the ion energy, the ion incidence angle, the ion fluence, together with the sample surface properties and temperature, have been proven to control in a complex and not completely codified manner the formation of periodically arranged dot, hole or ripple nanopatterns. In this work, we have studied how to apply ion beam sputtering to induce periodic ripples of specific aspect ratio on silicon surfaces, namely ripple height a of about 10 nm and period λ ≤ 50 nm, since these topographies can be appealing for technological applications. Silicon surfaces were irradiated with increasing O+ and Xe+ ion fluences at fixed ion energy and incidence angle. We have verified that some combinations of the chosen parameter values produced the desired structures. The obtained results also indicate that with a further refinement of those parameter values a better control of the aspect ratio of the obtained ripples is possible. Therefore, this work is a contribution to the final aim of exploiting ion beam sputtering as a fast, cost-effective and single-step method to fabricate well-controlled patterns over large surface areas at length scales beyond those of both standard and e-beam lithography.