• Low cost: This method uses basic equipment and an inexpensive, commercially available material to produce the pointed-tip arrays.
  
  
• Versatile: The template can be formed on a wide variety of substrates (e.g., glass, quartz, sapphire) and can be coated with various materials (e.g., zinc oxide [ZnO] and other semi-conductors, metal).
  
  
• Scalable: Unlike other methods which yield arrays of limited size, this process has the potential for large-scale (>4") fabrication of pointed-tip arrays.
  
  
• Simple: This three-step process is an easy alternative to materials synthesis and etching techniques, which are the current standards for making pointed-tip arrays.
  
  
• Consistent: The method yields a template of needle-like tips uniformly aligned and with a high aspect ratio
  

This technology is expected to provide a low-cost electron source useful in a wide range of electronics and mechanical equipment applications:

• Field emission displays
  
  
• Field emission devices
  
  
• Photocathodes
  
  
• Scanning tunneling microscopes
  
  
• Atomic force microscopes
  
  
• Far ultraviolet (UV) photo-lithography
  
  
• Low-power propulsion systems

Micron- and submicron-sized pointed structures are used in electrical and mechanical equipment applications where sharp tips are needed. However, existing methods to produce these structures—materials synthesis and etching—are plagued with difficulties. The equipment (e.g., deep reactive ion etching) can be very expensive, and the resulting arrays are small with tips/cones of varying heights and aspect ratios. However, a researcher at NASA Goddard Space Flight Center has developed a new, cost-effective process for producing large numbers of uniform point structures.

This innovative, low-cost process involves dropping or spinning a ferrofluid (i.e., a liquid containing Fe₂O₃ particles) onto a glass, quartz, or other substrate. A magnetic field is then applied using simple permanent or electro-magnets, causing the ferrofluid to form pointed structures that are uniformly aligned with a maximized aspect ratio. The ferrofluid then is dried at room temperature. The result is a template that can serve as a substrate for subsequent film growth through any standard thin-film deposition technique, including evaporation, sputtering, or chemical vapor deposition. (Templates have survived vacuum testing at 10^–6 Torr.) The conformal films applied to the template will reflect its pointed structure.

NASA’s ferrofluid technique may be particularly useful for creating emitters to be coated by wide bandgap semiconductors, which can absorb and emit electrons in the ultraviolet light bands. These materials, such as readily available ZnO, are an excellent alternative for the traditional large, high-voltage photocathode systems. Coating the templates created with Goddard’s technology with ZnO or other oxides avoids the oxidizing properties associated with metals typically used in photocathodes (e.g., tungsten, chromium). Therefore, the photocathodes are less susceptible to contamination, decay, and radiation damage and may be more chemically and structurally stable.

This technology is part of NASA’s Innovative Partnerships Program Office, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to consider licensing the Submicron-Sized Tips (GSC-14871-1) for commercial applications.

For information and forms related to the technology licensing and partnering process, please visit the Licensing and Partnering page. (Link opens new browser window)

If you are interested in more information or want to pursue transfer of this technology, please contact:

Innovative Partnerships Program Office
NASA Goddard Space Flight Center
Phone: (301) 286-2198
E-mail: submicron-tips@gsfc.nasa.gov