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

TL;DR

This study investigates the recrystallization behavior of nanocrystalline copper and silver films, revealing an inner size effect that accelerates diffusion and influences grain growth during annealing.

Contribution

It demonstrates the accelerated recrystallization linked to the inner size effect of diffusion coefficients in nanocrystalline metal films, with new insights into grain size evolution.

Findings

Bimodal grain size distribution in copper films persists during annealing.

Nanosized grains in silver films grow significantly after short-term annealing.

Diffusion coefficient in films is over 10^-18 m^2/s, indicating enhanced self-diffusion.

Abstract

This paper is devoted to studying the recrystallization of 100 nm thick polycrystalline films of copper and silver. It is found that in copper films deposited by the thermal evaporation method 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, micron-sized crystallites are present even in as-deposited Ag films besides the nanosized fraction. 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{\deg}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