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Process enables nanocircuits to stick to any substrate

Posted: 03 Aug 2011 ?? ?Print Version ?Bookmark and Share

Keywords:nanocircuits? substrate? silicon wafer?

Stanford University researchers have found a new way of fabricating nanowire-based circuits. The researchers were able to demonstrate a wafer-scale lift-off process that can be used to fabricate nanowire circuits onto reusable silicon wafers. The fabricated circuits can then be transferred to any substrate in any shape.

The research team, led by Xiaolin Zhen, believes that flexible circuitry can be used to create anything from paper-thin displays and solar cells to biomedical sensors that attach directly to the tissue being monitored.

"Devices can be transferred without sustaining any damage," said Zheng. "And the detachment process can be done at room temperature in just a few seconds."

Zheng worked on the fabrication with doctoral candidates Chi Hwan Lee and Dong Rip Kim.

The key to the novel process is depositing a sacrificial nickel layer atop a donor silicon wafer, which has been pre-coated with insulating silicon dioxide. Next, a flexible polymer just 800nm thick is deposited on the nickel, after which the nanowire circuitry (including FETs, diodes and resistors) is fabricated. Once the circuitry is finished, the wafer is submerged into water, which removes the nickel and the circuitry that is on the polymer substrate. The whole assembly can then be transferred to nearly any target substrate including paper, plastic, glass or metal.

nanowire-based circuits

After fabrication on a silicon wafer, nanowire-based circuits can be lifted off and transferred to any substrate in any shape.

"The lift-off process only separates the nickel from the silicon wafer," said Zheng. "The nickel can be etched afterwards to leave the polymer."

The silicon wafer is undamaged by the whole process, allowing it to be repeated over-and-over with the same waferthe donor silicon wafer is merely recoated with nickel before each reuse.

The detached circuitry uses nanowires just two microns long, allowing circuits to be deposited on nearly any shaped target substrate without substantial damage from crimping. The circuits can also be detached and reused, such as for biological sensors deposited on tissuelike the heartthen later removed and reused with other patients.

- R. Colin Johnson
??EE Times





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