CORVALLIS, Ore., March 21, 2006 -- A completely transparent integrated circuit made from inorganic compounds was made by researchers at Oregon State University (OSU), who say it is a major step in the field of transparent electronics.
The circuit is a five-stage "ring oscillator," commonly used in electronics for testing and new technology demonstration.
"This is a quantum leap in moving transparent electronics from the laboratory toward working commercial applications," said John Wager, a professor of electrical engineering at OSU. "It's proof that transparent transistors can be used to create an integrated circuit, tells us quite a bit about the speeds we may be able to achieve, and shows we can make transparent circuits with conventional photolithography techniques, the basic patterning methods used to create electronics all over the world."
Transparent electronics, scientists say, may hold the key to new industries, employment opportunities and new, more effective or less costly consumer products. Uses could range from transparent displays in the windshield of an automobile to cell phones, televisions, copiers, "smart" glass or game and toy applications. More efficient solar cells or better liquid crystal displays are possible.
A report on the findings has been accepted for publication in a professional journal, Solid State Electronics. The research was supported by the National Science Foundation, Army Research Office and HP. Recently, OSU also licensed to HP the rights to market new products based on this work, which provides the university a partner to help scale up and commercialize the technology.
Recently, OSU announced the creation of a transparent transistor based on zinc-tin-oxide. The new transparent integrated circuit is made from indium gallium oxide. Both of these compounds, which are amorphous heavy-metal cation multicomponent oxides, share some virtues: high electron mobility, chemical stability, physical durability and ease of manufacture at low temperatures. OSU said they will also be cost-effective and safe -- alternative heavy metals such as gold and silver have been ruled out because of their expense, and others such as mercury, lead or arsenic are avoided due to environmental concerns.
There are still challenges that need to be met, Wager said. The technology needs to be scaled up to larger sizes, all process steps must be functional for manufacturing, physical protection is needed for the new circuits, and new markets and products need to be identified. Work will continue toward developing a "P-channel" device would provide a number of advantages, such as lower power consumption, simple electronic architecture and the ability to do both analog and digital processing.
"What's exciting is that all of the remaining work seems very feasible," Wager said. "It will take some time, but we just don't see any major obstacles that are going to preclude the commercial use of transparent electronics with these
"In a way," Wager added, "it's shocking how fast this field has progressed. We might be able to bring transparent integrated circuits to widespread use in five years or so, a process that took a couple of decades in the early evolution of conventional electronics."
When perfected, the researchers said, some transparent electronics applications may be so cheap and effective that they could be used in "throw away" devices, or to replace conventional circuits that don't even require transparency. They said the electronic capabilities of the materials have already outperformed organic and polymer materials.
Collaborators on the work at OSU include Wager; Doug Keszler, professor and head of the chemistry department; Janet Tate, a professor of physics; and Rick Presley, a master's candidate in electrical engineering.
The project is affiliated with the Oregon Nanoscience and Microtechnologies Institute, a research collaboration involving Oregon's three public research universities -- OSU, Portland State University and the University of Oregon -- as well as the Pacific Northwest National Laboratory, the state of Oregon and the regional business community.
For more information, visit: eecs.oregonstate.edu