Experimental and computational insights in the growth of gallium-doped zinc oxide nanostructures with superior field emission properties

Abstract

Well-aligned, single-crystalline Ga-doped zinc oxide nanopagoda arrays were fabricated on silicon substrates via a metal–organic chemical vapor deposition method. Gallium atoms played a crucial role in transforming the lateral facets of nanorods from {100} to two sets of facets: ({111}, {11}) and ({201}, {10}), which eventually led to a pagoda shape. Based on computational simulation results, gallium lowers the surface energies of the ({111}, {11}) and ({201}, {10}) planes but increases that of the {100} plane. We proposed a new growth model, which involves the change of surface energy calculated by computational simulation due to Ga doping, to interpret why the smooth {100} planes of nanorods transform to corrugated ({111}, {11}) and ({201}, {10}) planes of nanopagodas. The nanopagodas not only possess excellent crystal quality but also exhibit remarkable field emission properties. Field emitters made of Ga-doped ZnO nanopagodas had a low turn-on field due to the decrease of work function and the increase of conductivity caused by Ga; simultaneously, the interesting pagoda shape enhanced significantly the field emission β values by 18 times.