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University of Wisconsin—Madison engineers fabricated a transistor that operates at a record 38 gigahertz. The team built the high-performance device using huge rolls of flexible plastic.

The transistor transmits data or transfer power wirelessly — a valuable capability for wearable electronics and sensor applications.

Using low-temperature processes, the University of Wisconsin-Madison researchers patterned the circuitry on their flexible transistor; single-crystalline silicon was ultimately placed on a polyethylene terephthalate (more commonly known as PET) substrate.

The engineers blanketed their single crystalline silicon with a dopant, and then added a light-sensitive material, or photoresist layer. Employing an electron-beam lithography technique, a focused beam of electrons created shapes as narrow as 10 nanometers wide.

The team applied the mold to an ultrathin, very flexible silicon membrane to create a photoresist pattern. A dry-etching process — essentially, a nanoscale knife — cut precise, nanometer-scale trenches in the silicon. Wide gates, which function as switches, were added atop the trenches.

With a unique, three-dimensional current-flow pattern, the high performance transistor consumes less energy and operates more efficiently. The narrower trenches enable semiconductor manufacturers to squeeze an even greater number of transistors onto an electronic device.

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