Unusual dislocation activity in Ge containing Sn particles

Abstract

We report an unexpectedly high dislocation activity around Sn inclusions in the Ge matrix below the brittle-to-ductile (BDT) transition temperature of Ge as observed using transmission electron microscopy. These dislocations nucleate at the Sn/Ge interface in form of dislocation loops upon solidification of Sn inclusions on cooling. The Sn inclusions solidify ~130 °C below the BDT of Ge. The novel feature is the unusual extent of dislocation loops so far from the inclusions, especially since the mobility of dislocations is limited in Ge below BDT. Considering the velocity of dislocation in Ge below the BDT to be ≈10−11 ms−1, it is normally not enough to increase the loop size from ≈1 nm to more than 300 nm in the short solidification time. We propose that in addition to diffusive type heat propagation, the sudden energy release upon solidification of Sn in Ge matrix can also be carried away by the expanding dislocation loops, thereby enhancing the velocity of dislocations significantly below the BDT. The role of expanding dislocation loops at Sn/Ge interface upon solidification of inclusions is thus fundamentally significant in understanding the rapid dissipation of latent heat from nanocrystalline inclusions embedded in a matrix.