Centered is a photo of a ZnO nanowire array on a 4 inch silicon wafer. It is surrounded by images of the array at different locations and magnifications. Scale bars, clockwise from upper left, correspond to 2 µm, 500 nm, 200 nm, and 1µm.

APPLICATIONS OF TECHNOLOGY:

• Nanoscale solar cells, light emission and display technologies
  

ADVANTAGES:

• Demonstrates a significant step towards commercial viability:
  
  • Cost efficient, low temperature (90° C) process
  • Permits batch fabrication - largest surface area yet reported for oriented nanowire arrays (up to at least 100 times the geometric area of the substrate)
    
  • Uniform average diameters between 30-120 nm and lengths between 0.2-5 µm
    
  • Can be grown on a variety of substrates including sapphire wafers, ITO glass, titanium foil, and flexible polymer films
    
  • Wires are aligned perpendicular to the substrate with a majority of the nanowires in solid contact with the substrate
    
  • Simple two-step procedure
    

ABSTRACT:

Berkeley Lab is offering for license a low temperature, mild solution process for fabricating large areas of homogeneous and dense arrays of nanowires on almost any substrate. Nanowire arrays can play a important role in miniaturizing energy conversion devices like solar cells and a variety of other optical, photonic, and electronic devices.

	Cross-sectinal scanning electron microscopy (SEM) image of a nanowire array grown on a silicon wafer for 1.5 hours.

While nanowires have been grown previously using low temperature processes, the Berkeley Lab technique is the first to achieve dense arrays of high quality nanowires over large surface areas and demonstrates a significant step towards commercial viability.

Peidong Yang and colleagues have synthesized ZnO nanowires with uniform diameters of less than 200 nm and varying less than 10%, and with lengths of 1-5 µm depending on the reaction time. They were grown on 4 inch silicon wafers and 2 inch plastic substrates. The wires are perpendicular to the substrate and most are in contact with the substrate to ensure a current pathway.

STATUS:

• Issued Patent # 7,545,051. Available for licensing or collaborative research.

PUBLICATION:

Greene L.E., Law M., Goldberger J., Kim F., Johnson J.C., Saykally R., Yang P., "Low-Temperature Production of ZnO Nanowire Arrays,” Angewandte Chemie International Edition 2003, 42, 3031-34.

Law, M., Greene, L.E., Johnson, J.C., Saykally, R., Yang, P., “Nanowire dye-sensitized solar cells," Nature Materials, 4, 455, 2005.

REFERENCE NUMBER: IB-1892

SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:

• Fabrication of Highly Luminescent Graded Core/Shell Nanocrystals and Simple Heterostructures (IB-1830)