Kinetics of intermetallic compound formation in thermally evaporated Ag-In bilayers

Abstract

The kinetics of intermetallic compound (IMC) formation in thermally evaporated Ag-In bilayers, with In on top of Ag, was investigated using X-ray diffractometry, applied to the surfaces of the bilayer specimens, as well as scanning electron microscopy, applied to cross-sections of the bilayer specimens, prepared by a focused ion beam instrument. IMC formation was followed at room temperature as well as at elevated temperatures of 50 ° C , 60 ° C, and 70 ° C. Two distinct growth regimes were observed coinciding with the availability of pure In. The AgIn2 IMC nucleated initially, followed by nucleation of the Ag2In IMC. The growth of AgIn2 was found to be controlled by both diffusional processes as well as interfacial reactions. The growth of the Ag2In IMC is dominantly diffusion-controlled. An interdiffusion coefficient of D = 1.1 ± 3.9 · 10−4 cm2 s−1 exp (− 60.5 ± 9.2 kJ mol−1 R−1 T−1 ) was obtained for the Ag2In IMC. The observations were discussed in terms of the interplay of thermodynamic and kinetic constraints.