Border trap characterization in metal-oxide-graphene capacitors with HfO2 dielectrics

In this work, a border trap model is employed to explain the observed frequency-dependent capacitance characteristics of metal-oxide-graphene (MOG) capacitors. Specifically, we have analyzed single-layer graphene capacitors with local-metal gates and HfO₂ dielectrics, a geometry which allows scaled dielectrics to be analyzed, and also avoids non-idealities associated with dielectric nucleation on graphene. In addition, this geometry allows us to compare our results with metal-insulator-metal (MIM) capacitors that utilize the same dielectric, thus allowing us to differentiate bulk HfO₂ effects from those associated with the graphene/dielectric interface. In this work, we compare the C-V characteristics of MOG capacitors with Hf02 dielectrics. Frequencydependent capacitance measurements indicate border-trap-like behavior at high temperatures and voltages, with trap density of - 1-2 x 1018 cm 3/eV, results similar to those obtained on MIM capacitors. At lower temperatures, the trapping mechanism freezes out, suggesting an interfacial layer between the graphene and HfO₂.