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Epitaxial lift-off of electrodeposited single-crystal gold foils for flexible electronics

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Science  17 Mar 2017:
Vol. 355, Issue 6330, pp. 1203-1206
DOI: 10.1126/science.aam5830

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Lifting off gold films

A method for growing and removing single-crystal gold films can be used to create a flexible and transparent substrate for devices. Mahenderkar et al. grew gold films on the face of a silicon wafer and then used photoelectrochemistry to undergrow a sacrificial silicon dioxide layer. This layer allowed the gold film to be peeled off with adhesive tape. A 28-nm-thick gold foil showed a minimal increase in sheet electrical resistance after 4000 bending cycles. Flexible films of single-crystal cuprous oxide and of zinc oxide nanowires were then grown on the gold foils.

Science, this issue p. 1203

Abstract

We introduce a simple and inexpensive procedure for epitaxial lift-off of wafer-size flexible and transparent foils of single-crystal gold using silicon as a template. Lateral electrochemical undergrowth of a sacrificial SiOx layer was achieved by photoelectrochemically oxidizing silicon under light irradiation. A 28-nanometer-thick gold foil with a sheet resistance of 7 ohms per square showed only a 4% increase in resistance after 4000 bending cycles. A flexible organic light-emitting diode based on tris(bipyridyl)ruthenium(II) that was spin-coated on a foil exploited the transmittance and flexibility of the gold foil. Cuprous oxide as an inorganic semiconductor that was epitaxially electrodeposited onto the gold foils exhibited a diode quality factor n of 1.6 (where n = 1.0 for an ideal diode), compared with a value of 3.1 for a polycrystalline deposit. Zinc oxide nanowires electrodeposited epitaxially on a gold foil also showed flexibility, with the nanowires intact up to 500 bending cycles.

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