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

摘要

A new optical method for the indirect determination of binary diffusion coefficientsof metals in binary nanoalloys is presented. Beginning with an initial nanobilayerof two pure metals, the method is based on the measurement of thevisible-light surface plasmon resonance (SPR) characteristic of the final alloynanolayer as a function of the diffusion process that occurred due to heattreatment at a constant temperature for a definite time. The theory behind isdescribed and an algorithm is developed that takes the initial thickness of thedeposited metal layers and the measured SPR angle of the final sample as inputand accordingly calculates the binary diffusion coefficient. The proposed algorithmhas been coded in the MATLAB simulator and applied to a fabricated initialAu–Ag bi-nanolayer (Au thickness 23 nm and Ag thickness 15 nm) which issubjected to a specific heat-treatment process (1 h at 100℃). The binary diffusioncoefficient is estimated as 6.94 ×10~(-17)cm~2 s~(-1), in agreement withreported 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.