Quantum Hall effect in multi-terminal suspended graphene devices

The integer and fractional quantum hall effects have been already observed in two terminal suspended graphene devices. However in this two probe device geometry, mixing between magnetoresistance $\rho_{xx}$ and Hall resistance $\rho_{xy}$ for incompletely developed quantum Hall states leads to substantial deviation of conductance plateaus values. In this talk, we present the experimental results from four terminal suspended graphene devices. The quality of quantum Hall effect will be discussed in muti-terminal device geometry in conjunction with the current-induced annealing process to improve the quality of graphene samples.