Fig. 1From: A Novel SERS Substrate Platform: Spatially Stacking Plasmonic Hotspots FilmsSEM images taken from the boundaries of the fabricated samples where the single- and dual-layer porous Au film structures can be clearly observed. The sputtering time of each layer of porous Au films changes from 19 to 75 s. a 19 s, b 28 s, c 37.5 s, d 47 s, e 56 s, and f 75 s. Annealing temperature: 200 °C. Scale bar is 500 nmBack to article page