Effects of Counteranions and Dissolved Oxygen on Chemical ZnO Deposition from Aqueous Solutions

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In the chemical ZnO deposition on Pd-catalyzed glass from aqueous dimethylamineborane (DMAB) solutions, effects of counteranions (NO3-, Cl−, ClO4-, and SO42-) and dissolved oxygen (DO) on the hydrolysis behavior of Zn2+ and the growth regime of ZnO were studied using sodium and zinc salt solutions bubbled with O2, air, or Ar gas. The interaction of the counteranions with H+ and Pd as well as Zn2+ was suggested as an important factor for the chemical ZnO deposition, and it was found that only NO3- can raise the pH of a DMAB solution without DO, affording the continuous ZnO growth. Dissolved oxygen accelerated the ZnO nucleation process on the Pd and had less influence comparable to NO3- on the subsequent growth on the ZnO surface. The ZnO films deposited from Zn(NO3)2–DMAB solutions bubbled with O2, air, or Ar gas were characterized with an X-ray diffractometer, field emission scanning electron microscope, UV-visible spectrophotometer, and Hall coefficient analyzer. The Ar-bubbled solution gave superior ZnO films in terms of crystallinity, growth orientation, surface morphology, and electrical conductivity due to the relatively moderate crystal nucleation compared to in the presence of DO.