Optoelectronic Characterization of ZnO Nanorod Arrays Obtained by Pulse Electrodeposition

ZnO nanorod arrays have been grown by potentiostatic pulse electrodeposition between a reduction potential and a "rest" potential. The effect of the duty cycle and pulse frequency as well as the heat-treatment in air on the properties of the electrodeposits has been studied. Surface morphology, structural, optical and electrical properties were evaluated. Absorption spectra reveal a high energy bandgap Burstein-Moss shift for the as-grown nanorods, in line with the donor density (1.1 x 10(19) and 9.5 x 10(19) cm(-3)) determined from electrochemical impedance spectroscopy. After annealing, the carrier concentration decreases to 10(17)-10(18) cm(-3), which is accompanied by an increase of the optical quality of the samples, assessed by the narrowing of the full width at half maximum of the near band edge recombination and steeper absorption at similar to 3.3 eV. The donor density and the flatband potential are dependent of the applied duty cycle and pulse frequency. All the analyzed samples evidence deep broad emission bands in the visible region, whose intensity is enhanced after annealing. The defect luminescence is due to an overlap of emitting centers in the red, yellow and green spectral regions, as evidenced and discussed by comparing the steady-state and transient spectroscopies. (c) 2018 The Electrochemical Society.