Possible application of laser-induced backside dry etching technique for fabrication of SERS substrate surfaces

Laser-induced backside dry etching (LIBDE) method has proved to be capable of micro- and nanomachining of transparent materials. In present study the applicability of this technique was tested to prepare surface structures that are suitable for surface enhanced Raman scattering (SERS) spectroscopy. Fused silica plates were coated with 16 nm thick silver layer by pulsed laser deposition (PLD) method. The metal absorbing film was irradiated and removed by 10 ArF excimer laser (λ = 193 nm, FWHM = 20 ns) pulses perpendicularly through the transparent samples at 1200 mJ/cm2 fluence. The remaining part of the silver coating was dissolved chemically shortly after the experiment using nitric acid. After this the etched holes were re-coated with 10, 20 and 40 nm thick silver layers by PLD, respectively. SERS activity of the different parts of the holes was investigated by a Thermo Scientific DXR Raman Microscope at 785 nm wavelength using 10−3 M aqueous solution of Rhodamin 6G as reference sample. SERS spectra were recorded at different areas of the holes having various roughness parameters. It was found that the intensity of the main peaks depended significantly on the surface morphology of the tested area and the thickness of its silver coating.