The effects of grain boundary scattering on the electrical resistivity of single-layered silver and double-layered silver/chromium thin films

The electrical resistivities both of single-layered Ag films with thicknesses of 9.0–198.0 nm, and double-layered Ag/Cr films deposited onto Ag base films of 9.0 and 99.0 nm thicknesses, with Cr overlayer films which have thicknesses of 11.0–27.0 nm and 26.0–56.0 nm respectively, are studied as a function of film thickness and temperature in the interval 90–300 K. Our analysis has shown that grain-boundary scattering is the dominant mechanism of the excess resistivity both for Ag and Ag/Cr films and the resistivity data could be analyzed in terms of the Mayadas–Shatzkes (M–S) model. Theoretical and experimental values of the R reflection coefficients of the electrons are calculated to be 0.32 and 0.35 for single-layered Ag films, and 0.46 and 0.45 respectively for Ag/Cr films, by taking an average over the whole temperature and thickness range studied. The reflection parameter R is also found to increase slightly with decreasing film thickness. This thickness-dependent variation of the reflection coefficient R indicates that the grain boundary scattering increases with decreasing Ag film thickness. According to our analysis, the observed increase in resistivity of the Ag/Cr films is caused dominantly by increased grain boundary scattering which corresponds to an increased value of the reflection parameter R of the Ag films, ranging from 0.35 to 0.46, and by increased residual resistivity due to deposition of the Cr films, with respect to those of the base Ag films. Interface scattering cannot be responsible for the excess resistivity of the Ag/Cr films.