Formation of nanoscale trenches and wires as a pathway to phase-separation in strained epitaxial Ge-Sn alloys

Abstract

We report on the molecular beam epitaxial growth of Ge 0.93Sn 0.07 alloys on Ge (100). A strained planar Ge 0.93Sn 0.07 film forms at the initial stages, as observed and confirmed by AFM and X-ray analysis. Continued deposition leads to formation of 3D Sn islands, which initiates phase-separation in the strained GeSn thin film through a kinetic pathway that leaves behind a pattern of nanoscale trenches and wires that run along 〈100〉directions. This morphological transition only happens in a certain range of temperature, thickness and composition. The morphological features observed in Ge 0.93Sn 0.07 films potentially offer a unique pathway for fabrication of nanostructures.