Shape-controlled synthesis of one-dimensional AlxGa1−xN nanotower arrays: structural characteristics and growth mechanism

Abstract

Tower-like AlxGa1−xN nanostructures with flat tops/sharp tips have been synthesized by catalyst-template-free chemical vapour deposition. Structural and morphological properties have been systematically investigated by x-ray diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. It has been found that typical tower-like nanostructures exhibit quasi-hexagonal nanocolumns stacking in layer-by-layer behaviour. The morphology of AlxGa1−xN nanotowers is strongly dependent on the evaporation temperature of precursors. A high evaporation temperature of precursors would induce the formation of a nanotower with large diameter and a flat top, and a low evaporation temperature of precursors would lead to the formation of a nanotower with small diameter and a sharp tip. The formation of AlxGa1−xN nanotowers has been proposed to be two-dimensional growth of hexagonal nanocolumns and one-dimensional stacking in the direction perpendicular to the previous nucleated section due to the existence of an Ehrlich–Schwoebel barrier. Raman scattering analysis reveals the hexagonal behaviour of tower-like nanostructures. The obtained nanotowers might have potential applications as functional blocks in future nanodevices.