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Schematic diagram of an all CVD graphene switch from (a) a cross sectional view and (b) a top view. The device consists of two layers of CVD-grown graphene. The bottom graphene is placed on a conductive substrate which functions as a bottom contact. The top graphene film is patterned into a beam with a length and width of and , respectively, and suspended above the bottom contact by a gap, . The top graphene beam is held in place via two top metal contact electrodes. The switch is activated through the application of a bias between top and bottom contacts.
Schematic side and top views [(a)–(d), left], photomicrographs [(a)–(c), right], and scanning electron micrographs [(d), right] of the fabrication process. (a) A large area CVD grown graphene layer is transferred by PMMA transfer onto a highly-doped Si substrate. (b) An insulating silicon dioxide layer is grown using PECVD, gold on chrome contact pads are patterned, and a second graphene layer is transferred on top using the same PMMA transfer method. (c) PMMA is spun on the surface and patterned to create beam structures, this is the “before” state. Using PMMA as an etch mask the pattern is transferred to the top graphene layer using oxygen plasma, this is the “after” state. (d) Finally, PMMA is stripped and the oxide layer is etched away to release the final structure.
Current-Voltage characteristics between the top and bottom contacts for a , device showing multiple switching transitions: (1) first scan, (3) third scan (plotted only from 0 to 5 V), and (4), the fourth and final scan.
Electrical and physical evidence of mechanical failure in large area CVD graphene switches. (a) I-V data of the graphene beam measured across the top contacts before and after switching measurements. (b) Scanning electron micrograph of a shorted device after testing. Inset is a magnified image of tear in graphene beam. Note that this image is flipped left-to-right relative to Fig. 2(d) (right).
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