Femtosecond laser machined nanostructures attracts several emerging fields over the past few decades for their wide range of applications in photonics and microfluidics. Intense femtosecond laser irradiation has revealed to be highly efficient for accurate processing of materials at the nanoscale and surface nano structuring due to the minimum thermal and mechanical damage of the materials during the short pulse irradiation. Our recent results on the study to understand the surface morphological changes under irradiation with ultrashort laser pulses by changing different input laser parameters such as laser fluence, laser pulse number, and incident laser polarization on Silicon and Germanium substrates will be discussed. Field emission scanning electron microscopy images reveal the formation of laser induced periodic sub-wavelength surface structures directly on bulk surface. The uniform periodic surface structures on semiconductor surfaces show prominent surface-enhanced Raman spectroscopy (SERS) applications. Gold films having different thickness are deposited on semiconductor (Si) surfaces on which periodic surface structures are fabricated by using femtosecond laser irradiation. The periodic structures are observed to be uniform over a large area with chain type structure formation of gold and Si. We have studied the influence of gold film thickness on the formation of these surface structures on Si surface by using different gold thickness deposited Si substrates. The conditions for the high enhancement factor in SERS with different gold thickness deposited samples will be presented [1-3].
References:
1) R Kuladeep, C Sahoo, L Jyothi, D Narayana Rao, V Saikiran Journal of Material Science 57, 1863–1880 (2022).
2) V Saikiran, Mudasir H Dar, D Narayana Rao Appl. Surf. Science 428, (2018) 177-185.
3) V. Saikiran, Mudasir H Dar, R. Kuladeep, D. Narayana Rao MRS Advances, Volume 1, Issue 49 (Electronics and Photonics) 2016, pp. 3317-3327.
Giovanni Mattei
