Single and Co-Doping of ZnO Nanowires with Al and Cl Using One Precursor by Chemical Bath Deposition

The simultaneous cationic and anionic co-doping of ZnO nanowires grown by chemical bath deposition offers great promise to optimize the performance of engineering devices, but its development has not been achieved yet. Here, we explore the single doping with Al and Cl using Al(NO3)3 and NH4Cl as chemical additives to investigate their effect on the morphology and properties of ZnO nanowires, and we extend the approach to their simultaneous co-doping using AlCl3 as the only chemical additive. The single and co-doping processes of ZnO nanowires with Al and Cl are achieved in the high-pH region regardless of the chemical additive, where Al(OH)4- complexes and Cl- ions are predominantly formed and readily adsorb on the positively charged m-plane sidewalls through attractive electrostatic forces. Using the simultaneous co-doping approach, we reveal significant interplay effects between Al(III) and Cl(I) species through competitive adsorption and incorporation processes. Both Al(III) and Cl(I) species act as capping agents, but the former predominantly affect the morphology of ZnO nanowires over the latter and its presence on their surfaces is more pronounced. The incorporation of Al dopants is further found to be larger than the incorporation of Cl dopants owing to energetic considerations. Interestingly, the thermal annealing under oxygen atmosphere usually performed to activate the Al doping of ZnO nanowires results in the opposite migration processes of Al dopants toward the bulk and of Cl dopants toward their surfaces. Eventually, the formation of hydrogen-related defects including interstitial hydrogen and VZn-nH complexes is more impacted by Al doping than by Cl doping. These findings report the simultaneous cationic and anionic co-doping of ZnO nanowires with Al and Cl using one single chemical additive as an additional way to tune their physical properties and facilitate their integration into engineering devices.

Automated summary

The simultaneous cationic and anionic co-doping of ZnO nanowires with Al and Cl using one single chemical additive offers a promising way to optimize their physical properties and facilitate their integration into engineering devices. In this study, we investigate the effect of single doping with Al and Cl and extend the approach to their simultaneous co-doping. The co-doping process reveals significant interplay effects between Al(III) and Cl(I) species through competitive adsorption and incorporation processes.