ABSTRACT
Ag-Co films with ultra-high resistivity were prepared on polyimide by magnetron sputtering. The effect of Co content and annealing temperatures on the resistivity and microstructure of Ag-Co films has been thoroughly investigated and the relation between resistivity and microstructure has been discussed. Results show that thicker Ag-Co films without annealing present lower resistivity due to better crystallinity. However, thin Ag-Co films (≤21 nm) annealed at 360 °C present ultra-high film resistivity because of the formation of diffusion pits on the film surface which blocks the transmission of electrons in films to increase film resistivity. Inversely, the resistivity of thick Ag-Co films (≥45 nm) annealed at 360 °C is much less than that annealed at lower than 260 °C owing to no diffusion pits. Furthermore, the addition of Co inhibits the growth of Ag grains and limits the migration of electrons in Ag-Co films further, also resulting in the increase of Ag-Co films' resistivity.
ABSTRACT
Mo-48.2% Ag films were fabricated by direct current (DC) magnetron sputtering and annealed in an argon atmosphere. The effects of annealing on the surface morphology, resistivity and surface-enhanced Raman scattering (SERS) performance of Mo-48.2% Ag films were investigated. Results show a mass of polyhedral Ag particles grown on the annealed Mo-48.2% Ag films' surface, which are different from that of as-deposited Mo-Ag film. Moreover, the thickness and the resistivity of Mo-48.2% Ag films gradually decrease as the annealing temperature increases. Furthermore, finite-difference time-domain (FDTD) simulations proved that the re-deposition Ag layer increases the "hot spots" between adjacent Ag nanoparticles, thereby greatly enhancing the local electromagnetic (EM) field. The Ag layer/annealed Mo-48.2% Ag films can identify crystal violet (CV) with concentration lower than 5 × 10-10 M (1 mol/L = 1 M), which indicated that this novel type of particles/films can be applied as ultrasensitive SERS substrates.
