Control of Ni-Sn interfacial reactions through reactant design

The reaction of modulated elemental films containing Ni and Sn was studied as a function of composition and annealing temperature. In contrast to bulk diffusion couples where Ni3Sn4 is found to interfacially nucleate regardless of overall composition, the identity of the first compound nucleated from the modulated reactants is controlled by the initial composition of the reactant. Ni3Sn4 was observed to nucleate on deposit for films with compositions close to that of this binary compound. Ni3Sn2 and Ni3Sn were the first crystalline compounds nucleated from films near their respective compositions. These films were amorphous on deposit, however, requiring annealing temperatures of 400 °C to nucleate these binary compounds. Films prepared with compositions between those of the known binary compounds were amorphous on deposit and directly formed the expected thermodynamic mixtures of the known binary compounds without any crystalline intermediates. The previously reported metastable compound NiSn was not observed in this investigation.