Research ArticleAPPLIED SCIENCES AND ENGINEERING

Ultratransparent and stretchable graphene electrodes

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Science Advances  08 Sep 2017:
Vol. 3, no. 9, e1700159
DOI: 10.1126/sciadv.1700159
  • Fig. 1 Schematic illustrations and morphological characterizations of MGGs.

    (A) Schematic illustration of the fabrication procedure for MGGs as a stretchable electrode. During the graphene transfer, backside graphene on Cu foil was broken at boundaries and defects, rolled up into arbitrary shapes, and tightly attached onto the upper films, forming nanoscrolls. The fourth cartoon depicts the stacked MGG structure. (B and C) High-resolution TEM characterizations of a monolayer MGG, focusing on the monolayer graphene (B) and the scroll (C) region, respectively. The inset of (B) is a low-magnification image showing the overall morphology of monolayer MGGs on the TEM grid. Insets of (C) are the intensity profiles taken along the rectangular boxes indicated in the image, where the distances between the atomic planes are 0.34 and 0.41 nm. (D) Carbon K-edge EEL spectrum with the characteristic graphitic π* and σ* peaks labeled. (E) Sectional AFM image of monolayer G/G scrolls with a height profile along the yellow dotted line. (F to I) Optical microscopy and AFM images of trilayer G without (F and H) and with scrolls (G and I) on 300-nm-thick SiO2/Si substrates, respectively. Representative scrolls and wrinkles were labeled to highlight their differences.

  • Fig. 2 Comparison of electrical and optical properties of MGGs and graphene.

    (A) Four-probe sheet resistances versus transmittance at 550 nm for several types of graphene, where black squares denote mono-, bi-, and trilayer MGGs; red circles and blue triangles correspond with multilayer plain graphene grown on Cu and Ni from the studies of Li et al. (6) and Kim et al. (8), respectively, and subsequently transferred onto SiO2/Si or quartz; and green triangles are values for RGO at different reducing degrees from the study of Bonaccorso et al. (18). (B and C) Normalized resistance change of mono-, bi- and trilayer MGGs and G as a function of perpendicular (B) and parallel (C) strain to the direction of current flow. (D) Normalized resistance change of bilayer G (red) and MGG (black) under cyclic strain loading up to 50% perpendicular strain. (E) Normalized resistance change of trilayer G (red) and MGG (black) under cyclic strain loading up to 90% parallel strain. (F) Normalized capacitance change of mono-, bi- and trilayer G and bi- and trilayer MGGs as a function of strain. The inset is the capacitor structure, where the polymer substrate is SEBS and the polymer dielectric layer is the 2-μm-thick SEBS.

  • Fig. 3 Exploration of CNTs as a replacement of graphene scrolls.

    (A to C) AFM images of three different densities of CNTs (CNT1<CNT2<CNT3) on graphene. (D) Optical transmittances of G-CNT-G on quartz. (E) Normalized resistance change of G-CNT-G as a function of strain. Transmittance and normalized resistance change of trilayer MGGs are listed as a comparison.

  • Fig. 4 Understanding the strain tolerance of conductivity of various graphene structures.

    (A to H) In situ AFM images of trilayer G/G scrolls (A to D) and trilayer G structures (E to H) on a very thin SEBS (~0.1 mm thick) elastomer at 0, 20, 60, and 100% strain. Representative cracks and scrolls are pointed with arrows. All the AFM images are in an area of 15 μm × 15 μm, using the same color scale bar as labeled. (I) Simulation geometry of patterned monolayer graphene electrodes on the SEBS substrate. (J) Simulation contour map of the maximal principal logarithmic strain in the monolayer graphene and the SEBS substrate at 20% external strain. (K) Comparison of crack area density (red column), scroll area density (yellow column), and surface roughness (blue column) for different graphene structures.

  • Fig. 5 Demonstration of stretchable and transparent all-carbon transistors.

    (A) Scheme of graphene-based stretchable transistor. SWNTs, single-walled carbon nanotubes. (B) Photo of the stretchable transistors made of graphene electrodes (top) and CNT electrodes (bottom). The difference in transparency is clearly noticeable. (C and D) Transfer and output curves of the graphene-based transistor on SEBS before strain. (E and F) Transfer curves, on and off current, on/off ratio, and mobility of the graphene-based transistor at different strains.

  • Fig. 6 Demonstration of stretchable LED control units by all-carbon transistors.

    (A) Circuit of a transistor to drive LED. GND, ground. (B) Photo of the stretchable and transparent all-carbon transistor at 0% strain mounted above a green LED. (C) The all-carbon transparent and stretchable transistor used to switch the LED is being mounted above the LED at 0% (left) and ~100% strain (right). White arrows point as the yellow markers on the device to show the distance change being stretched. (D) Side view of the stretched transistor, with the LED pushed into the elastomer.

  • Table 1 Comparison of the transmittance at 550 nm and the normalized resistance change at designated strains of the two types of graphene structures.

    N/A, not applicable.

    Transmittance
    at 550 nm (%)
    (RR0)/R0
    at 50%
    (RR0)/R0
    at 100%
    Mono-G/G scrolls95.91.96N/A
    Bi-G/G scrolls91.61.223.86
    Tri-G/G scrolls88.50.240.54
    G-CNT1-G94.62.077.29
    G-CNT2-G91.31.394.72
    G-CNT3-G87.40.722.22

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/9/e1700159/DC1

    Experimental section

    Additional supporting information

    fig. S1. Optical microscopy images of monolayer MGG on SiO2/Si substrates at different magnifications.

    fig. S2. SEM images of mono-, bi-, and trilayer MGGs on the SiO2/Si wafers.

    fig. S3. SEM images of graphene film covered with spray-coated CNTs.

    fig. S4. Comparison of two-probe sheet resistances and transmittances @550 nm of mono-, bi- and trilayer plain graphene (black squares), MGG (red circles), and CNTs (blue triangle).

    fig. S5. Sheet resistances of mono-, bi-, and trilayer MGGs.

    fig. S6. Optical transmittances of MGGs and multilayer plain graphene.

    fig. S7. Normalized resistance change of mono- and bilayer MGGs (black) and G (red) under ~1000 cyclic strain loading up to 40 and 90% parallel strain, respectively.

    fig. S8. Calculation of relative areal capacitance change as a function of strain.

    fig. S9. Optical microscopy image of trilayer MGG on SEBS elastomer.

    fig. S10. SEM image of trilayer MGG on SEBS elastomer after strain, showing a long scroll cross over several cracks.

    fig. S11. AFM images of various graphene structures on SEBS elastomer after 100% strain.

    fig. S12. AFM image of trilayer MGG on very thin SEBS elastomer at 20% strain, showing that a scroll crossed over a crack.

    fig. S13. Optical microscopy observation and simulation of graphenes on SEBS under strain.

    fig. S14. Contact resistances of monolayer G/CNTs and Au/CNTs at different gate voltages.

    table S1. Mobilities of bilayer MGG–single-walled carbon nanotube transistors at different channel lengths before and after strain.

    table S2. Summary of recent work on all-carbon transistors.

    movie S1. Demonstration of stretchable LED control units by all-carbon transistors.

    References (5458)

  • Supplementary Materials

    This PDF file includes:

    • Experimental section
    • Additional supporting information
    • fig. S1. Optical microscopy images of monolayer MGG on SiO2/Si substrates at different magnifications.
    • fig. S2. SEM images of mono-, bi-, and trilayer MGGs on the SiO2/Si wafers.
    • fig. S3. SEM images of graphene film covered with spray-coated CNTs.
    • fig. S4. Comparison of two-probe sheet resistances and transmittances @550 nm of mono-, bi- and trilayer plain graphene (black squares), MGG (red circles), and CNTs (blue triangle).
    • fig. S5. Sheet resistances of mono-, bi-, and trilayer MGGs.
    • fig. S6. Optical transmittances of MGGs and multilayer plain graphene.
    • fig. S7. Normalized resistance change of mono- and bilayer MGGs (black) and G (red) under ~1000 cyclic strain loading up to 40 and 90% parallel strain, respectively.
    • fig. S8. Calculation of relative areal capacitance change as a function of strain.
    • fig. S9. Optical microscopy image of trilayer MGG on SEBS elastomer.
    • fig. S10. SEM image of trilayer MGG on SEBS elastomer after strain, showing a long scroll cross over several cracks.
    • fig. S11. AFM images of various graphene structures on SEBS elastomer after 100% strain.
    • fig. S12. AFM image of trilayer MGG on very thin SEBS elastomer at 20% strain, showing that a scroll crossed over a crack.
    • fig. S13. Optical microscopy observation and simulation of graphenes on SEBS under strain.
    • fig. S14. Contact resistances of monolayer G/CNTs and Au/CNTs at different gate voltages.
    • table S1. Mobilities of bilayer MGG–single-walled carbon nanotube transistors at different channel lengths before and after strain.
    • table S2. Summary of recent work on all-carbon transistors.
    • References (54–58)

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mp4 format). Demonstration of stretchable LED control units by all-carbon transistors.

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