The challenge in building high performance electronic devices from carbon nanotubes or graphene lies in integrating them into circuits without destroying their unique properties. In particular, when creating nanocarbon transistors for wireless applications making an efficient gate electrode has proven difficult.
One way to improve performance is to create freestanding 3-dimensional gate structures. Unfortunately, this is quite difficult using conventional photolithography or electron beam lithography. This instructable will show a fast and easy way how to create a suspended gate electrode for high frequency nanoelectronics.
Step 1: Preparations
- Chunk of graphite
- Scotch tape
- Silicon wafer
- Microscopes: optical, AFM, SEM
- Clean room facilities
- Focused ion beam (handy but not absolutely necessary)
Making graphene is fairly straightforward: take a piece of graphite and rub it over the silicon wafer. Then use the scotch tape to peel of layers until you end up with a single layer left on the substrate. You can check the process with an optical microscope: if the layer is only barely visible anymore you have (probably) succeeded.
Step 2: Lithography
Step 3: Metallization
Step 4: Bridging
A organic precursor gas is decomposed by the focused Ga-ion beam resulting in local deposition of a conducting compound. The metal covered resist layer protects the sensitive graphene sheet from any gallium ion implantation or irradiation damage.
(In principle it is also possible, yet more difficult, to achieve this in a second lithography process.)
Step 5: Release
Step 6: Lift-off
- Special precaution stepsprecaution steps might be necessary to prevent capillary forces during drying from collapsing the bridge
- Performance can be increased further when the graphene sheet itself is subsequently suspended by etching away the sacrificial layer