Substructure of intermetallic thin-film Cu$_{3}$Sn

The crystalline structure of intermetallic Cu$_{3}$Sn synthesized by successively condensing thin layers of copper and tin on a substrate at 150$^{\circ}$C has been studied. Cu$_{3}$Sn compound exists in a very narrow homogeneity range and has a long-period close-packed ordered D0$_{19}$ superstructure. It has been found that the crystal lattice exhibits many slip traces associated with dislocation motion. The dislocation motion is due to the stressed state of the crystal, which can be characterized as uniform extension. Electron micrographs show that slip traces in the Cu$_{3}$Sn crystal are parallel to the ($\bar{11}$21) and (11$\bar{2}$1) planes belonging to pyramidal slip system II, which is a main slip system along with pyramidal and basal ones. Slip traces result from the motion of partial dislocations, as indicated by the amount of slip, which is equal to half the interplanar distance. Since the crystal is ordered, slip is accomplished by a pair of superpartial dislocations and a slip trace may be a superstructural or complex stacking fault.