Atomic Pathways of Solute Segregation in the Vicinity of Nanoscale Defects

Using GeSn semiconductor as a model system, this work unravels the atomic-level details of the behavior of solutes in the vicinity of a dislocation prior to surface segregation in strained, metastable thin layers. The dislocations appear in the 3D atom probe tomography maps as columnar regions, 3.5-4.0 nm wide, with solute concentrations 3-4 times higher than the sounding matrix. During the initial stage of phase separation, the migration of solute atoms toward the dislocation is associated with a gradual increase in Sn concentration and in density of atomic clusters, which reach 175-190 per 10(3) nm(3) with 12-15 atoms/cluster close to dislocations. The latter provide, at advanced stages, fast diffusive channels for Sn mass-transport to the surface, thus bringing the matrix around the dislocation to the equilibrium concentration. In parallel, an increase in solute concentration (similar to 0.05 at. %/nm) and in the number of atomic clusters (12-16 clusters/33 nm) is observed along the dislocation core.

Automated summary

This study using GeSn semiconductor as a model system reveals the atomic-level details of solute behavior near a dislocation before surface segregation in strained, metastable thin layers. The migration of solute atoms towards dislocations during the initial phase separation leads to an increase in Sn concentration and density of atomic clusters.