Large-scale Fabrication of Vertically Aligned ZnO Nanowire Arrays

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Zhong Lin Wang
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Wenzhuo Wu
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Yaguang Wei
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Rene' Meadors

Background: Nanowires (NWs) are metallic or semiconducting particles that have a high aspect ratio, extremely small cross-sectional diameters («1 micron - µm) and lengths as long as tens of microns. Well-aligned one-dimensional NW arrays can be used in photo-electrodes for solar energy conversion because they provide direct electrical pathways, large junction areas and low reflectance properties to assist in light scattering and trapping. Metal oxide NW arrays such as ZnO with large surface areas and short diffusion lengths for minority carriers represent a new class of photo-electrode materials with great promise for photo-electrochemical  hydrogen generation applications and solar converters.

Technology:  Zhong Lin Wang, Yaguang Wei, and Wenzhuo Wu from the School of Materials Science and Engineering have developed an invention that proposes a novel approach for large-scale fabrication of vertically aligned ZnO NW arrays with applicability for any substrate using textured ZnO seed layer. The NWs created by this approach have the same diameter of around 1 µm and are perfectly aligned normal to the substrate with the same height of around 2 µm. The hexagonal shape achieved using this approach demonstrates excellent single crystal growth along a particular direction.

In this approach, a dense layer of aligned ZnO NWs are grown on a substrate using a low temperate hydrothermal process. An optimized, multi-step growth process allows for perfect alignment of ZnO NW grown on top of each other. The NWs grown have top facets that can be patterned and used for subsequent growth of vertically aligned ZnO NWs array. The top facets for the NWs that are formed on a flat surface using this approach can be easily patterned and used for subsequent fabrication of vertically aligned arrays. Using substrates that can sustain high temperature processes also fabrication of vertically aligned nanowire arrays using physical vapor deposition methods.

Potential Commercial Applications: This invention demonstrates a cost-effective method of manufacturing large-scale, well-aligned 1-dimensional ZnO nanostructures at high throughput rates and lower costs. These can be used for different applications ranging from energy harvesting, sensing and electronic devices. The approach also paves the path towards integrating the structures into devices on general substrates.

Benefits / Advantages:

  • ZnO nanostructures that are applicable in energy harvesting, sensing, flexible electronics, optoelectronics, piezo-electronics and plasmonics
  • Allows fabrication of large-scale uniformly patterned nanostructures at higher throughput rates and lower cost
  • Consistent diameter (~1 µm)  and height (~2 µm)
  • The top facets of the grown NWs form a flat surface and can be patterned or used for growth of vertically aligned arrays