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

Graphene transfer is a crucial step for fabricating any graphene-based device. The transfer is particularly challenging when the application requires the graphene to be freestanding. This is the case for variable capacitors, which can be used for energy harvesting from vibrations. In our research, we transfer graphene over an array of holes that have been etched into a silicon wafer. We begin with commercially available multilayer graphene grown on a nickel/silicon substrate. We spin-coat PMMA onto the graphene/Ni/Si substrate. Next, we exfoliate graphene/Ni from the Si substrate using scotch tape. We then etch away the nickel leaving us with a tape/PMMA/graphene stack which is robust and easy to handle. Next, we align and press the tape/PMMA/graphene stack over the array of holes mentioned earlier. We chemically remove the tape/PMMA material using acetone and only the multilayer graphene remains. The final step is to use a critical point dryer. This transfer method produces samples with suspended graphene over the holes, which are verified using electrical resistance and capacitance measurements.