Ga-doped ZnO self-assembled nanostructures obtained by microwave-assisted hydrothermal synthesis: Effect on morphology and optical properties

Abstract

Highly homogeneous gallium doped ZnO assembled nanostructures comprised by thin hexagonal platelets showing a striking preferred orientation along the ab plane have been obtained by an ultra-fast and eco-friendly microwave-assisted hydrothermal synthesis method. Although the incorporation of gallium into the ZnO lattice is found to be relatively low, namely ≤1 mol.%, the gallium nitrate addition plays a key role in the size and morphology of the obtained ZnO nanostructures. The observed morphology is attributed to the selective adsorption of the gallium species on the basal planes of ZnO, which inhibits the growth along the ± [0001] direction. Additionally, the optical band-gap and the fluorescence emission are modified upon gallium addition. The observed changes in the optical properties are ascribed to both the decreased crystal size and to the gallium incorporation into the ZnO structure, which lead to the modification in the energy levels.