Fractal microstructure of Ag film via plasma discharge as SERS substrates* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11874140, 12064017, and 61765008), the Science and Technology Project of Changzhou, China (Grant Nos. CJ20210130, CJ20190046, and CJ20200073), and the Postgraduate Research and Practice Innovation Program of Jiangsu Province, China (Grant Nos. B200203143 and KYCX20 0433).

Abstract

According to the atmospheric pressure plasma (APP) technology, we propose a rapid synthetic approach of the substrates for enhanced Raman spectroscopy. The plasma is used to modify and etch the surface of silver film, which generates large scale hotspots’ aggregation. By switching the discharge polarity and adjusting the film thickness, different surface morphologies are formed due to the oxidation, reactive etch and accumulation of the plasma product in a certain space. Especially under positive corona discharge condition, dense snake-like microstructures are formed by the gradual connection of individual nanoparticles, which are driven by the influence of the electric field on surface diffusion. In addition, the experiments verify that the corresponding enhancement factor (EF) raises at least five orders of magnitude and the treatment time is about 10 min.