Graphene Field-Effect Transistor Array Fabrication

Graphene was prepared on a piece of copper foil (99.8%, Alfa Aesar, Tewksbury, MA) by low-pressure chemical vapor deposition at 1020°C in a H₂(99.999% purity, 80 standard cubic centimeters per minute (sccm)) and CH₄(99.999% purity, 10 sccm) atmosphere. Graphene was then transferred via a bubbling transfer method [18 (link)] onto a 52-device electrode array, as shown in Fig 1a. The electrode arrays were pre-patterned on a Si wafer with 285 nm SiO₂. The SiO₂/Si wafer was spin-coated with PMGI (Kayaku Advanced Materials Inc., Westborough, MA) and S1813 photoresist (Kayaku Advanced Materials Inc.), followed by a standard photolithography process. The patterned wafer was developed by MF-319 developer (Kayaku Advanced Materials Inc.) for 45s. The contact metallization was 5nm Cr and 40 nm Au, deposited by thermal evaporation at a rate of 1 Å /s. Then the wafer was incubated in remover 1165 (Kayaku Advanced Materials Inc.) for liftoff. Another level of lithography process and O₂ plasma etching technique (0.8 Torr pressure; 60 W power; 30 s duration) were used to define a 100 μm×10μm graphene channel. The remaining photoresist was stripped by remover 1165. Finally, the GFET arrays were annealed in an Ar/H₂ atmosphere (Ar flow rate 1000 sccm; H₂ flow rate 250 sccm) at 225 °C for 1 h to remove any residues from the photolithographic processing before use.