Synthesis of aluminium-doped ZnO nanocrystals with controllable morphology and enhanced electrical conductivity

In this work, aluminium-doped zinc oxide nanocrystals (AZONs) with controllable morphology and enhanced electrical conductivity are successfully prepared via a solvothermal method and a subsequent calcination process. Thus obtained near-spherical AZONs with an average particle size of 40 nm show a minimum volume resistivity of ∼22.38 Ω cm, which is eleven orders of magnitude lower than that of pure ZnO. The remarkable enhancement of electrical conductivity is mainly ascribed to the homogenous incorporation of Al3+ into wurtzite ZnO lattice. In addition, the calcination under hydrogen atmosphere further improves electrical conductivity, which is deemed to be caused by the bonding of hydrogen to the lattice oxygen and oxygen vacancy. All these defects result in the generation of free electrons and therefore increase the charge carrier concentration.