Controlled hydrothermal growth of vertically-aligned zinc oxide nanowires using silicon and polyimide substrates

• Controlled hydrothermal growth of ZnO nanowires on silicon (Si) and polyimide (PI).
• Influence of substrate on grain size of seed layer been investigated.
• Grain roughness and diameter was found to be larger on PI than on Si.
• ZnO nanowires found to have larger diameter on PI than on Si.
• Reported process can be implemented to grow ZnO nanowires on any substrate.

In this paper, hydrothermal synthesis combined with microfabrication techniques is used for growing vertically-aligned zinc oxide (ZnO) nanowires (NWs) on zinc (Zn) seed layers patterned on silicon (Si) and polyimide (PI). The NWs have shown a hexagonal crystalline structure and vertical orientation. The substrate material together with the hydrothermal precursor concentration has shown to influence the diameter and length of the NWs. Atomic force microscopy and scanning electron microscopy have revealed that the substrate material affects the grain size of the deposited seeds and consequently the morphology of the NWs which show a diameter in the range 100–220 nm and 130–400 nm when grown on Si and PI, respectively. NWs grown with an optimised concentration of 2 mM are densely packed and vertically-aligned with a consistent uniform distribution on both types of substrates.

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