Fabrication of Gated Corbino Discs on CVD Grown, Monolayer Graphene

Using commercially available, CVD grown, monolayer graphene deposited on thermally oxidized silicon wafers, we have fabricated a variety of test structures that are suited for on-chip probing. The test structures include Corbino discs with inner disc diameters ranging from 20 $\mu$m to 120 $\mu$m and gap lengths ranging from 55 $\mu$m to 105 $\mu$m. Additionally, a new type of structure that we call the twinaxial Corbino ellipse was fabricated on the same chip with minor axes set to 230 $\mu$m and major axes that varied from 276 $\mu$m to 460 $\mu$m. Inner disc electrodes with diameters ranging from 20 $\mu$m to 120 $\mu$m were placed at the foci of the elliptical devices. Our fabrication process involved the use a sacrificial aluminum layer, which prevented delamination during metal lift-off processes and kept polymer residues from degrading Ohmic contact quality. Gated current-versus-voltage traces from the Corbino discs revealed Dirac point operation corresponding to gate voltage values, which exhibited dependence on device dimensions and drain-to-source bias, ranging from 5 V to 15 V.