Diffusion of Au into Sn thin films studied by the attenuated total reflection method

The diffusion of Au into Sn thin films has been measured from 20 to 40 0C. Diffusion rates were determined using the method of attenuated total reflection which measures the absorption resonance in the reflection spectrum caused by plasmon excitation on the dielectric-metal interface. By observing the incident angle at which the reflection is a minimum, the thickness of the unreacted Au layer can be determined, and thus the thickness of the alloy phase in each stage can be calculated. The diffusion rate at 20 0C is found to be D = 1.9 x 10-14 cm2 s-1, and the activation energy for the formation of AuSn is 22.6 kcal/mole