Optical band gap blue shift and stokes shift in Al-doped ZnO nanorods by electrodeposition

A preparation process for Al-doped ZnO nanorod arrays by electrodeposition from an aqueous solution of Zn(NO3)2, NH4NO3 and Al(NO3)3 was established. The inevitable growth of the layered nanostructures due to the use of Al(NO3)3 was suppressed by the use of NH4NO3. Consequently, the use of the additives results in the fabrication of the high quality ZnO nanorod arrays. In addition, the properties of ZnO nanorods such as the diameter, density, distance, and weight ratio of Al/Zn were adjusted by controlling the Al(NO3)3 concentration in the electrolyte. The increase of the carrier concentration as a result of Al doping leads to the blue shift of the optical band gap in ZnO nanorods (3.64-3.65 eV), which is ascribed to the Burstein-Moss effect. The Stokes shift of Al-doped ZnO nanorods is in the range of 215-225 meV, indicating a large nonradiative recombination in the nanorods.