Graphene transfer over an array of tip-well structures on SiO2/Si substrate for harvesting energy from graphene vibrations

Due to graphene’s ultimate thinness, its flexibility is 1000 times that of the best silicon nitride cantilevers causing it to move under the influence of even pico-Newton size forces. Due to this property, graphene shows great promise in vibration energy harvesting. In our effort to make a device for harvesting energy from graphene vibrations, a cone-shaped tip has been etched in SiO2/Si substrate. The tip resides inside a 7-microns wide well, which is connected to a trench. Gold is deposited over the tip-well-trench structure to make a two-contact device, where the trench-end forms the tip contact, and the top of the well forms the second contact. In this study we present the procedure for transferring graphene above the tip region in preparation for making a graphene variable capacitor for vibration energy harvesting. Our graphene samples are grown on a nickel film on the top of a silicon wafer. Our first step is to peel off the graphene-nickel layer with a scotch-tape. Next, we etch nickel in iron III chloride solution. Avoiding airdrying which shorts graphene to the tip, we transfer the isolated graphene membrane in deionized water, and then place it above the tip structure region. Finally, we use critical point drying to remove the fluid between graphene and the well. After graphene transfer, we do optical and electrical characterization to confirm graphene suspension.