A new synthesis route of ZnO nanonails via microwave plasma-assisted chemical vapor deposition

In this work, a new method to obtain zinc oxide nanonails (ZnO-NNs) via microwave plasma-assisted chemical vapor deposition (MAP-CVD) is reported. The ZnO-NNs were grown on cobalt seeds using He as the carrier gas. The cobalt seeds were deposited onto alumina at different distances from the substrate to the precursor material via the sputtering technique. The ZnO-NNs were characterized by SEM, TEM, SAED, HRTEM and EDX. NNs growth was uniform on the substrate surface: the stem of these structures ranged between 250 and 450 nm, the cap ranged between 25-150 nm, and the necks ranged between 30-200 nm. The wide distribution of the NNs dimensions was due to the vapor from the thermal decomposition of ZnO, which is richer in gaseous species of Zn than oxygen, leading to the formation of oxygen vacancies. The rich Zn vapor triggers the growth in a different direction to the shank of the cap forming the NNs, which grows in the direction [1010]. Some structural and experimental aspects are discussed in this paper.