Solid-state synthesis of Cu$_6$Sn$_5$ intermetallic in Sn/Cu thin films

The study results of solid-state synthesis of the Cu$_6$Sn$_5$ intermetallic in the Sn/Cu thin-film systems during vacuum annealing from room temperature to $300^\circ$C are presented. The initiation and finishing temperatures of the solid-state reaction between the Cu and Sn nanolayers and the phase composition of the reaction products were determined. The synthesized thin films were monophasic and consisted of the hexagonal $\eta$-Cu$_6$Sn$_5$ phase. It is assumed that the initiation temperature of the solid-state reaction in Sn/Cu thin films is associated with the start temperature of the reverse polymorphic transformation $\eta' \rightarrow \eta$ between the monoclinic and hexagonal Cu$_6$Sn$_5$ phases.