Thermal stability of Ag films in air prepared by thermal evaporation

The thermal stability of silver films in air has been studied. Pure Ag films, 250 mn in thickness, were prepared on glass substrates by thermal evaporation process, and subsequently annealed in air for I h at temperatures between 200 and 400 degrees C. The structure and morphology of the samples were investigated by X-ray diffraction, Raman spectra and atomic force microscopy. It is found that the crystallization enhances for the annealed films, and film surface becomes oxidized when annealing temperature is higher than 350 degrees C. The electrical and optical properties of the films were studied by van der Pauw method and spectrophotometer, respectively. Reflectance drops sharply as Ag films are annealed at temperatures above 250 degrees C. Film annealed at 250 degrees C has the maximum surface roughness and the minimum reflectance at 600 nm optical wavelength. Film annealed at 200 degrees C has the minimum resistivity, and resistivity increases with the increasing of the annealing temperature when temperature is above 200 degrees C. The results show that both oxidization on film surface and agglomeration of silver film result in infinite of electrical resistivity as the annealing temperature is above 350 degrees C. (c) 2007 Elsevier B.V. All rights reserved.