Surface Modification and Applications Laboratory (SMAL)

Research Areas

Ion beam induced surface nanostructuring

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.

Self assembly of colloidal droplets

Self-assembly is a process which generates structural organization of particles at all scales in the absence of any additional external forces. Evaporation of nanofluid droplets commonly termed as Coffee Ring Effect is such a process where particles accumulate at the edge of the droplet. Interesting desiccation patterns are formed after complete evaporation of the droplets. This pattern formation is affected by factors such as type, concentration and shape of the nanoparticles, temperature, humidity and nature of the substance.

In our group, we examine the effect of nanoscale roughness of substrate on the deposition pattern. Interactions involved in the process such as DLVO interaction and capillary interaction as a consequence of varying roughness are examined. We also explore magnetic nanoparticle arrangement under varying magnetic fields utilizing the evaporative self-assembly process.

Light interactions at structured interfaces

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.

Research Funding Received(External)

  1. DST-SERB Project No. CRG/2018/001258, Influence of self-affine and periodic surface fluctuations on 'Coffee ring effect, INR 47.01400 Lakhs (2019 - 2022)

  2. DST-SERB Project No. SR/S2/CMP-0112/2012, Investigation of pattern formation in binary alloy systems, INR 39.38750 Lakhs (2013 - 2016)

  3. CSIR Project No. 03/1289/13/EMR-II, Scaling and related studies on chemically eroded surfaces, INR 8.44000 Lakhs (2014 - 2017)

Funding Agencies