Spatial elemental investigations in nanostructured alloyed Ag/Au SERS substrates by magnetron sputtering oblique-angle co-deposition towards increased performance and shelf life

This work proposed thorough investigations of Ag/Au alloy SERS substrates at different element compositions that allowed the highest SERS performance. Film-based slanted alloy nanorod arrays were prepared by a magnetron sputtering oblique-angle co-deposition. With silicon substrates mounted at 86 degrees oblique angle, the SERS samples were prepared towards varying alloyed compositions, to be individually separated into 6 x 6 sample grid. Each of which was physically observed by field-emission scanning electron microscopy (FE-SEM), and elementally analyzed by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy. The SERS performance was finally investigated with a confocal Raman spectroscopy. The results showed that the Ag/Au slanted nanorods were partially isolated. The smallest Au sputtering power mostly introduced irregularly shaped nanostructures. The higher the power, the more well-observed the nanorods became. In addition, the increased power source also affected the average dimensions of the nanorods. The EDS contour-plotted results showed the Au percentage gradually decreased from the position closest to farthest from the source, with the atomic Au percentage ranged from 0 up to 40%. Finally, the Raman performance was investigated across all gridded SERS samples and the highest SERS activities were obtained from the sample with the 23% Au content.