Fabrication and Characterization of Biplasmonic Substrates Obtained by Picosecond Laser Pulses

Featured Application Fabricated structures can be used as substrates for the SERS technique of Raman spectroscopy. Bimetallic nanostructures have the potential to become the new generation candidates for applications in catalysis, electronics, optoelectronics, biosensors and also for surface-enhanced Raman Spectroscopy (SERS). The bimetallic nanocrystals offer additional properties over the single metal components such as improved electromagnetic properties and corrosion protection. This work presents a simple and inexpensive method to fabricate large area biplasmonic (bimetallic) substrates, employing DC magnetron sputtering, picosecond laser pulses and a digital galvanometric scanner. The aim of this study was to achieve large area homogeneous substrates while having a good and predictable signal amplification by SERS effect. Gold thin films with 200 nm thickness were deposited on optical polished substrates and then irradiated in atmospheric air with lambda = 1064 nm wavelength laser pulses with 8 ps pulse duration and 500 kHz fixed repetition rate. Various laser fluences and laser irradiation speeds were employed in order to optimize the Laser-Induced Periodic Surface Structures (LIPSS) formed on the substrate. The results are presented comparatively for the standalone Cu substrates and for the Cu-Au substrates using Raman spectral analysis on a single signal peak of a Rhodamine 6G solution.