Evolution of the faceting, morphology and aspect ratio of gallium oxide nanowires grown by vapor-solid deposition

Gallium oxide nanostructures with high aspect ratio and variable faceting were synthesized by the chemical vapor deposition method via vapor-solid growth mechanism. Systematic investigation of the growth conditions revealed that these nanowires can be produced under the conditions of high temperature and low precursor flow. The nanowires crystalize as the β-phase Ga ₂O₃, which has the monoclinic crystal structure. Preferred growth was along the [0 1 0] direction, as corroborated with lattice-resolved imaging and crystal plane models. The high degree of faceting is discussed in terms of the evolution of the nanowire cross section morphology, based on the growth rate of the facet boundaries relative to the nanowire surface planes. The obtained nanowires show intense blue emission, characterized by a broad-band photoluminescence spectrum with a maximum at 430 nm and long decay time. This emission arises from the defect-related donor-acceptor pair recombination mechanism, and depends on the nanostructure dimensionality and morphology. The possible influence of controlled nanowire faceting on the observed optical properties is also discussed. Owing to their morphology-dependent optical properties, these nanowires are promising building blocks for electronic and optoelectronic structures and devices.