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
  • Fig. 1 Schematic for epitaxial lift-off of single-crystal Au foil.

    (A) Miscut n-type Si(111) wafer without the native oxide layer. (B) Epitaxial electrodeposition of Au on Si(111) from a 0.1 mM HAuCl4 solution at –1.9 V versus Ag/AgCl with prepolarized electrode. (C) Photoelectrochemical oxidation of Si under irradiation of light in 0.5 M H2SO4 solution at 0.75 V versus Ag/AgCl. (D) A polymer adhesive (tape/hot glue) is applied to the surface of Au to aid the foil separation. (E) A sacrificial SiOx interlayer is etched using dilute (5%) hydrofluoric acid to separate the foil from the Si substrate. (F) Single-crystal Au foil completely detached from the Si surface.

  • Fig. 2 Electron microscopy of the single-crystal Au, epitaxial Cu2O, and epitaxial ZnO.

    (A and B) High-resolution TEM cross section of epitaxial Au on Si without the SiOx interlayer for the as-deposited film (A) and with the SiOx layer after photoelectrochemical oxidation of Si (B). (C to F) Surface morphology of Au foils deposited for 5 min (7 nm) (C), 10 min (11 nm) (D), 20 min (21 nm) (E), and 30 min (28 nm) (F). (G) Electrodeposited epitaxial Cu2O on 30-min Au foil. (H) Electrodeposited ZnO nanowires on 10-min Au foil subjected to 500 bending cycles.

  • Fig. 3 X-ray diffraction and pole figures to study the in-plane and out-of-plane orientation.

    (A) Out-of-plane orientation of electrodeposited Au(111) on Si(111). (B) Out-of-plane x-ray diffraction showing satellite peaks (Laue oscillations) caused by constructive and destructive interference. (C) Out-of-plane orientation of Au(111) foil, electrodeposited Cu2O on 30-min Au foil, and electrodeposited ZnO on 10-min Au foil. (D to G) In-plane orientation was determined using (220) pole figure of Si(111) (D), (220) pole figure of Au(111) foil (E), (220) pole figure of Cu2O(111) on Au(111) foil (F), and (102) pole figure of ZnO(002) on Au(111) foil (G). The radial lines in the pole figure correspond to 30° increments of the tilt angle.

  • Fig. 4 Transmittance, sheet resistance, and flexibility of Au foils with diode and OLED fabrication.

    (A) Wafer-size Au foil with diameter of 50.8 mm and thickness of 28 nm. (B) Transmittance and sheet resistance of Au foils as a function of thickness. (C) Sheet resistance of Au foils with thicknesses of 11, 16, and 28 nm as a function of bending cycles with a bending curvature of 3 mm. (D) Current-voltage response of Au foil/RuII(bpy)3/InGa junction, showing rectifying behavior. Inset: Red-orange electrogenerated chemiluminescence of RuII(bpy)3BF4 OLED on flexible 28-nm-thick Au foil. (E) Current-voltage response of Cu2O diode on Au foil (epitaxial) and stainless steel (polycrystalline) substrates. (F) Dark saturation current density (Js) and diode quality factor (n) of epitaxial and polycrystalline Cu2O diodes measured using log(J) versus V at forward bias.

Supplementary Materials

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

    Naveen K. Mahenderkar, Qingzhi Chen, Ying-Chau Liu, Alexander R. Duchild, Seth Hofheins, Eric Chason, Jay A. Switzer

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S11
    • References

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