Posted on 07/25/2006 5:08:34 PM PDT by annie laurie
New thin-film semiconductor techniques invented by University of Wisconsin-Madison engineers promise to add sensing, computing and imaging capability to an amazing array of materials.
Historically, the semiconductor industry has relied on flat, two-dimensional chips upon which to grow and etch the thin films of material that become electronic circuits for computers and other electronic devices. But as thin as those chips might seem, they are quite beefy in comparison to the result of a new UW-Madison semiconductor fabrication process detailed in the current issue of the Journal of Applied Physics.
A team led by electrical and computer engineer Zhenqiang (Jack) Ma and materials scientist Max Lagally have developed a process to remove a single-crystal film of semiconductor from the substrate on which it is built. This thin layer (only a couple of hundred nanometers thick) can be transferred to glass, plastic or other flexible materials, opening a wide range of possibilities for flexible electronics. In addition, the semiconductor film can be flipped as it is transferred to its new substrate, making its other side available for more components. This doubles the possible number of devices that can be placed on the film.
By repeating the process, layers of double-sided, thin-film semiconductors can be stacked together, creating powerful, low-power, three-dimensional electronic devices.
"It's important to note that these are single-crystal films of strained silicon or silicon germanium," says Ma. "Strain is introduced in the way we form the membrane. Introducing strain changes the arrangement of atoms in the crystal such that we can achieve much faster device speed while consuming less power."
For non-computer applications, flexible electronics are beginning to have significant impact. Solar cells, smart cards, radio frequency identification (RFID) tags, medical applications, and active-matrix flat panel displays could all benefit from the development. The techniques could allow flexible semiconductors to be embedded in fabric to create wearable electronics or computer monitors that roll up like a window shade.
"This is potentially a paradigm shift," says Lagally. "The ability to create fast, low-power, multilayer electronics has many exciting applications. Silicon germanium membranes are particularly interesting. Germanium has a much higher adsorption for light than silicon. By including the germanium without destroying the quality of the material, we can achieve devices with two to three orders of magnitude more sensitivity."
That increased sensitivity could be applied to create superior low-light cameras, or smaller cameras with greater resolution.
Ma, Lagally, Materials Science and Engineering Assistant Professor Paul Evans, Physics Associate Professor Mark Eriksson, and graduate students Hao-Chih Yuan and Guogong Wang are patenting the new techniques through the Wisconsin Alumni Research Foundation. The team's work was supported in part by grants from the National Science Foundation Materials Research Science and Engineering Center, the Department of Energy and the Air Force Office of Scientific Research.
Ping
"Germanium has a much higher adsorption for light than silicon"
I look forward to flexible solar panels (sheets sounds more like it!) instead of the bulky rigid panels. If you could integrate them into windows, or on architectural panels for commercial buildings it might cut down on the daytime energy costs for heating and cooling. All depends on the cost, and that is not something they discussed.
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is Germanium as plentiful as silicon? Or is it easier to make pure?
Cost is the main reason why solar panels aren't more plentiful today.
These minds that create such amazing technology are astounding. Imagine the applications for a low-energy, high power, flexible chip like this. Thanks for posting the article.
There are companies that are in the process of building inkjetable and flexible displays just as you've posted. The circuits, memory, battery all are "sprayed" on and ultimately will lead to things like that picture from Red Planet. Others will be movie posters...that are actually movies, on posters(obviously short clips but you get the point). It's still out a number of years yet, but it's coming.
If the smarts are small enough, it shouldn't matter whether or not they themselves are flexible or merely affixed to or in flexible things (like buttons or sequins on cloth). The interconnects are another story.
Not sure I'd trust anything coming out of Madison, WI. :-)
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