Ag Surface Outflow Kinetics in Ag/AlN Nanomultilayers

Abstract

The heat‐induced microstructure evolution of nanomultilayers (NMLs) with metallic components is widely studied due to its critical importance in ensuring the reliable application of these nanomaterials. The thermal degradation of NMLs is controlled by mass transport of one of the NML components from the NML volume to its surface. The outflow occurs at temperatures well below the melting point of metal, offering new opportunities for the engineering of innovative NML‐based brazing fillers. A combined experimental‐modeling approach for the quantitative analysis of silver (Ag) outflow kinetics in Ag/AlN NMLs is presented. The method is based on in situ monitoring of the X‐ray diffraction intensity evolution of Ag acquired from the near‐surface region of NML (grazing incidence geometry) upon annealing in the temperature range of 230–425 °C (atmosphere of N2). The experimental data are compared to model predictions of Ag diffusion. It is assumed that Ag diffusion is driven by the relaxation of residual stresses in Ag nanolayers. Due to the multilayer geometry, the surface outflow kinetics are mainly defined by the kinetics of Ag diffusion along Ag/AlN interphase boundaries. The parameters defining the Ag surface outflow kinetics, i.e., diffusion coefficients and activation energy for diffusion, are derived.