AFRL Team Demonstrates Effectiveness of In-House Transparent Transistor Technology

  • Published
  • By Molly Lachance
  • AFOSR
ARLINGTON, Va. --  AFRL scientists demonstrated world-record performance of transparent transistors created by a team of in-house sensors scientists. Composed of thin-film nanocrystalline zinc oxide, the novel transistors can function undetected on clear surfaces such as glass or plastic. Lead investigator Dr. Burhan Bayraktaroglu and his team are responsible for developing and testing these transparent devices. The technology's combination of high channel mobility, mechanical flexibility, and high optical transparency at room temperature make it an excellent candidate for supporting a wide range of future Air Force electronics needs and applications.

Potential applications include video image displays and coatings for windows, visors, and windshields; electrical interconnects for integrated, multimode, remote sensing focal plane arrays; high-speed microwave devices and circuits for telecommunications and radar transceivers; and semitransparent, touch-sensitive screens for emerging multitouch interface technologies. Another attractive aspect of this new thin-film type of transistor is that the processing technology used to fabricate the devices is not only relatively simple but also compatible with inexpensive plastic and flexible substrate technology.

The AFRL team discovered that controlling transistor conductivity and transparency is a matter of optimizing the size and density of constituent zinc oxide nanocrystals. The successfully demonstrated films are 90% to 95% transparent, have metallike electrical conductivities, and can withstand high temperatures for long periods without degrading.

Dr. Bayraktaroglu and his team have used these devices to demonstrate the world's first thin-film microwave transistor. They have also perfected the application of zinc oxide films onto various surfaces using a special technique called pulsed laser deposition, which employs an ultraviolet laser beam to first remove zinc oxide nanocrystals from a source and then deposit them as a thin film on the desired surface. Through standard lithography techniques, these films then undergo the processing needed to produce field-effect transistors and transparent conductors.