Accelerated recrystallization of nanocrystalline films as a manifestation of the inner size effect of the diffusion coefficient

Abstract

The work is devoted to the study of recrystallization occurring during short-term annealing of 100 nm thick polycrystalline films of copper and silver. It is found that in copper films deposited by the method of thermal evaporation onto a substrate at room temperature, a bimodal crystallite size distribution with maxima at 15 and 35 nm is observed. The bimodal distribution in copper films is preserved during annealing, which leads to a shift of both peaks of the crystallite size distribution histograms to the larger sizes region. In contrast to Cu, even in as-deposited Ag films, besides the nanosized fraction, micron-sized crystallites are present. Apparently, these grains are formed due to the phenomenon of self-annealing and weakly evolve during heating owing to grain growth stagnation. The nanosized fraction in as-deposited Ag films is represented by crystallites with the most probable size of 25 nm, which increases to 50 nm as a result of short-term annealing at the temperature of 250 °C. The grain-boundary diffusion coefficient was determined, which is more than 10−18 m2/s for both films of metals. The obtained value indicates a multiple intensification of self-diffusion processes in films, the thickness of which allows us to refer them to macroscopic sample.