SERS Detection of Rhodamine-6G on Ion Beam Nanostructured Ultra-Thin Gold (Au) Films: A Correlation between Fractal Growth, Water Contact-Angle and Raman Intensity

SERS (Surface Enhanced Raman Scattering) detection of rhodamine-6G on gold nanostructures (Au-NS) of various sizes under ion beam irradiation is presented. On a glass substrate, Au thin films of different thicknesses (similar to 2, 3 and 5 nm) were deposited by thermal evaporation. Subsequent irradiation using 10 keV Ar+ at different fluences has been able to modify the size of Au-NS. Ion beam-induced sputtering and diffusion processes control the formation of Au-NS. The reduction in Au content during ion beam sputtering is confirmed by Rutherford Backscattering Spectroscopy (RBS), which also validates tuning the size and structures of Au-NS. The wettable characteristics of Au-NS surfaces are controlled by two competing statistical factors of sputtering and surface diffusion. A correlation between the water contact angle, rms roughness, and the detection of rhodamine-6G (R6G) by SERS is presented. The current study sheds light on the mechanism(s) of SERS chemical detection for wider metallic surfaces.