Diffusion of Al into Au thin films studied by the ATR method

Alloy formation in Au-Al thin films has been studied by the attenuated total reflection (ATR) method in the 64-80 degrees C temperature range. In this optical method, the coupling of incoming light with a surface plasmon at the metal-dielectric interface appears as a sharp minimum in the reflectance spectrum of p-polarized light. The angular position of this minimum is very sensitive to the optical constants of the metal near the interface. This makes the method suitable for studies of diffusion in metals. In the presence of unreacted aluminum, the energy of activation for the growth of Au(2)Al is found to equal 22.9 kcal/mole.