Surface morphology evolution behavior and SERS performance of Mo-Ag-Cu-Co films

Mo-Ag-Cu-Co films were fabricated by co-sputtering Ag/Mo and Co/Cu composite targets. Results show that a large number of particles grew on the surface of Mo-Ag-Cu-Co films before and after annealing. The number, size and components of these self-grown particles could be adjusted and controlled by changing annealing temper-atures. The differences in diffusion of Ag, Cu, Co and Mo in Mo-Ag-Cu-Co films is the major mechanism of forming nanoparticles with different components. As the annealing temperature was lower than 260 ?C, the self -formed particles were Ag single-crystal particles due to the stronger diffusion ability of Ag at low annealing temperatures. The stronger diffusion ability of Cu promotes the formation of AgCu particles after annealing at higher temperatures. However, the number of Ag atoms is much more than that of Cu atoms, which results in the presence of Ag particles. It was the first time that the monodispersed Ag particles and Ag-Cu particles were obtained on alloy films by magnetron sputtering without any template. These alloy films as SERS substrates presented excellent SERS performance and detected the characteristic Raman spectrum of 5 x 10(-12) mol/L rhodamine 6g (R6G) solution, which could be ascribed to the enhanced electromagnetic field among hetero-geneous particles.