The influence of AZO films on morphology and surface plasmon resonance properties of Ag particles

Ag particles based Al-doped zinc oxide (AZO) films on glass substrates were prepared by magnetron sputtering method and then thermal annealing treatment. The crystallization quality and surface morphology of AZO films and thermal annealing treatment have an important effect on the thermal diffusion growth of Ag particles, which can greatly determine the morphology, size distribution and surface plasmon resonance (SPR) properties of Ag. Compared with spherical Ag particles, the elongated Ag elliptical particles formed on AZO films with better crystalline quality and smaller surface roughness after annealing exhibit red shift of SPR peaks. An effective finite difference time domain (FDTD) model is built to investigate the SPR mechanism of elongated elliptical Ag particles. It is found that elongated elliptical Ag particles are more likely to exhibit SPR properties in long wavelengths intensely depending on transverse surface plasmon (TSP) and longitudinal surface plasmon (LSP) modes. The large average particle size and decrease of inter-particle spacing of elongated elliptical Ag particles corresponding to LSP mode lead to the redshift of SPR. Moreover, the elongated elliptical Ag particles with large long axis distance could be more conductive, and RS value of those Ag based AZO film reaches to 9.6 Ω/sq after annealing at 350 °C.