Rapid fabrication of bilayer graphene devices using direct laser writing photolithography

In this work the authors establish the use of the photolithography technique by direct laser writing for fabrication of devices on bilayer graphene coated with a photoresist. This technique is simple to use, versatile, reliable, and capable of achieving good throughput. The alignment of the patterns with the graphene flakes and between different lithography steps can be performed with an accuracy of about 0.5 μm allowing the placement of electric contacts and the definition of the Hall-bar geometries in an effective way. The devices fabricated were characterized by four-terminal resistance measurements as a function of the back gate and the Hall effect. The devices show initially p-type doping, but after annealing inside the cryostat at 127 °C in a He atmosphere, the samples become n-type. Different temperature dependence resistivity behaviors are found in bilayer graphene samples with high and low carrier densities. This approach offers a high degree of flexibility for fabrication of graphene devices.