Study of optical and electrical properties of Ag films deposited on different substrates

Ag films with the normal thickness (d) ranging from 25 nm to 200 nm were deposited on anodic aluminum oxide (AAO) templates (200 nm pore diameter) and quartz substrates by thermal evaporation technique. The effects of thickness on the structure, optical and electrical properties are investigated. The microstructure is studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical and electrical properties are measured by spectrophotometer and Van der Pauw method, respectively. The results show that the crystalline performance of the Ag films on quartz substrates (QuartzAg) is better than that of the Ag films on AAO templates (AAOAg). When d=200 nm, the nanoparticles in AAOAg film pile up. Total reflectance (R) of both AAOAg and QuartzAg films increases with the increase of d. But R of AAOAg film is much lower than that of QuartzAg film. As d is 109 nm, R of QuartzAg film is higher than 95% in the visible and near infrared optical regions, while R of AAOAg film is only 40%. The QuartzAg film with 25 nm thickness is conductive, but d of the conductive AAOAg film must be larger than 37 nm. At the same d, the sheet resistance of AAOAg film is higher than that of QuartzAg film. The difference of sheet resistance between AAOAg and QuartzAg films decreases from 4.90 Ω/ to 0.37 Ω/ as d increases from 37 nm to 200 nm.