Effect of Zr contents and covering Ag layer on Microstructure and SERS properties of Cu nanoparticles / Cu-Mo-Zr alloy films on flexible substrates

Cu-Mo-Zr alloy films with different Zr contents were prepared by magnetron sputtering. The microstructure and SERS properties of alloy films were characterized by SEM, TEM, XRD and Raman spectroscopy. A large number of Cu nanoparticles are formed spontaneously on the surface of alloy film after annealing. Moreover, the number, size and particle spacing of Cu nanoparticles are found to be highly sensitive to annealing temperature, annealing time, Zr content and film thickness. Results of the local electric field between Cu particles on the alloy films surface simulated by FDTD reveal that larger particles and smaller spacing can produce stronger local electric fields. Furthermore, a 10 nm Ag layer coating on the alloy film has a significant effect on the size, spacing of Cu particles, and the synergistic enhancement between Ag layer and Cu nanoparticle can significantly increase the local electric field thereby improving the SERS performance of Cu-Mo-Zr alloy films. The Raman signal of 10-13 mol/L Rhodamine 6G solution can be detected by using Ag layer/Cu-30 at% Mo-22.9 at% Zr alloy films as SERS substrates. The present study provides a method for preparing SERS substrates with low cost, high sensitivity and excellent repeatability.