A Novel Optical Method for Nondestructive Determination of Binary Diffusion Coefficients in Metal Nanoalloy Films

Abstract

A new optical method for the indirect determination of binary diffusion coefficients of metals in binary nanoalloys is presented. Beginning with an initial nano‐bilayer of two pure metals, the method is based on the measurement of the visible‐light surface plasmon resonance (SPR) characteristic of the final alloy nanolayer as a function of the diffusion process that occurred due to heat treatment at a constant temperature for a definite time. The theory behind is described and an algorithm is developed that takes the initial thickness of the deposited metal layers and the measured SPR angle of the final sample as input and accordingly calculates the binary diffusion coefficient. The proposed algorithm has been coded in the MATLAB simulator and applied to a fabricated initial Au–Ag bi‐nanolayer (Au thickness 23 nm and Ag thickness 15 nm) which is subjected to a specific heat‐treatment process (1 h at 100 °C). The binary diffusion coefficient is estimated as 6.94 × 10−17 cm2 s−1, in agreement with reported values for thin films. The novel method is nondestructive, simple, fast, and highly sensitive to changes of concentration profiles throughout multilayers, a few tens of nanometer that exhibit the SPR phenomenon.