Surface-mediated tunable self-assembly of single crystal semimetallic ErSb/GaSb nanocomposite structures

Arrays of metallic nanostructures embedded within a semiconducting matrix are of great interest for applications in plasmonics, photonic crystals, thermoelectrics, and nanoscale ohmic contacts. We report a method for growing single crystal arrays of semimetallic vertical and horizontal ErSb nanorods, nanotrees, and nanosheets embedded within a semiconducting GaSb matrix. The nanostructures form simultaneously with the matrix and have epitaxial, coherent interfaces with no evidence of stacking faults or dislocations as observed by high-resolution transmission electron microscopy. By combining molecular beam epitaxy growth and in situ scanning tunneling microscopy, we image the growth surface one atomic layer at a time and show that the nanostructured composites form via a surface-mediated self-assembly mechanism that is controlled entirely at the growth front and is not a product of bulk diffusion or bulk segregation. These highly tunable nanocomposites show promise for direct integration into epitaxial semiconductor device structures and also provide a unique system in which to study the atomic scale mechanisms for nucleation and growth.