Effect of Thickness of the Poly(vinyl alcohol) Passivation Layer on Ambipolar Characteristics of Graphene Field-effect Transistor

Pristine graphene field-effect transistor (GFET) typically has an ambipolar transport characteristic. However, unintentional doping during fabrication and post-fabrication typically leads to p-doping of the graphene layer. This unintentional doping is further exacerbated when the GFET is operated in an ambient environment rich with oxygen and water molecules. In this work, the recovery of the ambipolar transport characteristics of the GFET by passivating the graphene with poly(vinyl alcohol) (PVA) is demonstrated. Two approaches were considered, i.e. drop casting and spin coating. It is found that the spin coating approach produces a rather uniform PVA film with thickness ~0.83 μm. It can recover and further retain the ambipolar transport characteristics of GFET in ambient environments. By manipulating the number of ions in the PVA, it is believed that the characteristics could be prolonged making GFET more suitable for sensing in ambient environment.