Sol-gel synthesis and characterization of Ag nanoparticles in ZrO_2 thin films

摘要

ZrO_2 thin films containing silver nanoparticles were prepared using the sol-gel method with Ag to Zr molar ratios [Ag]/[Zr] = 0.11, 0.25, 0.43, 0.67, 1.00, 1.50, and 2.33. After dip coating on glass substrate, coated films were annealed at 200 and 300 ℃ in air. X-ray diffraction peaks corresponding to crystalline Ag were observed, but a specific peak corresponding to ZrO_2 was not observed. At the molar ratio [Ag]/[Zr] = 0.25, the particle size of Ag distributed broadly centered at 17 nm for an annealing temperature of 200 ℃ and at 25 nm for 300 ℃. The films annealed in air at 200 ℃ showed an absorption band centered at 450 nm because of the silver surface plasmon resonance, whereas films heated at 300 ℃ in air caused a red shift of the absorption to 500 nm. The absorption peak was analyzed using the effective dielectric function of ZrO_2-Ag composite films modeled with the Maxwell-Garnett expression.