Surface Modification and Applications Laboratory (SMAL)

Ion beams are used in a manifold of ways to engineer surfaces of semiconductors, metals, insulators, polymers, 2D materials., etc. which have wide applications in areas like plasmonics, solar cells, magnetism, electronics and biophysics. The patterning becomes possible since bombarding a solid surface with energetic ions produces self-organized nanopatterns depending upon the ion beam parameters. Being a single step clean process with easily tunable beam parameters, it can create patterns in wafer scale area within a extremely small time interval.

We study the pattern formation processes for single and multi-elemental surfaces which essentially comprises of a competitive process between a negative surface tension and a surface relaxation mechanism. For non-elemental surfaces, however, the individual elemental diffusivities and sputtering yields bring in an extra factor of instability. This instability in binary compound triggers to form nanopatterns with compositional and topological fluctuations on its surface.

Light upon interacting with different media undergoes various phenomenon like transmission, refection, absorption, TIR, etc. The situation however gets different when light interacts with metal nano structures. The electric field interacts with the free electron plasma of the conductor resulting in collective oscillation of the electrons which is known as Localized surface plasmon resonance (LSPR). Owing to this a high electric field is generated around metal nano-structures which is exploited in various applications i.e EOT (extra-ordinary transmission), surface enhanced Raman scattering (SERS) and several others.

Our study focuses on the optical response of such metal nano-structures including its transmission, reflection and surface enhanced Raman scattering behavior. We fabricate different kinds of metal nano-structured templates or pre-patterned solid material templates by using low energy ion beams as well as chemical etching methods.