Structural and compositional evolutions of InxAl1−xN core–shell nanorods grown on Si(111) substrates by reactive magnetron sputter epitaxy

Abstract

Catalystless growth of InxAl1−xN core–shell nanorods have been realized by reactive magnetron sputter epitaxy onto Si(111) substrates. The samples were characterized by scanning electron microscopy, x-ray diffraction, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. The composition and morphology of InxAl1−xN nanorods are found to be strongly influenced by the growth temperature. At lower temperatures, the grown materials form well-separated and uniform core–shell nanorods with high In-content cores, while a deposition at higher temperature leads to the formation of an Al-rich InxAl1−xN film with vertical domains of low In-content as a result of merging Al-rich shells. The thickness and In content of the cores (domains) increase with decreasing growth temperature. The growth of the InxAl1−xN is traced to the initial stage, showing that the formation of the core–shell nanostructures starts very close to the interface. Phase separation due to spinodal decomposition is suggested as the origin of the resultant structures. Moreover, the in-plane crystallographic relationship of the nanorods and substrate was modified from a fiber textured to an epitaxial growth with an epitaxial relationship of InxAl1−xN[0001]//Si[111] and InxAl1−xN[11]//Si[1 by removing the native SiOx layer from the substrate.