  We have analyzed the breakdown of the quantum Hall effect in 1 micrometer
wide Hall devices fabricated from an exfoliated monolayer graphene transferred
on SiOx. We have observed that the deviation of the Hall resistance from its
quantized value is weakly dependent on the longitudinal resistivity up to
current density of 5 A/m, where the Hall resistance remains quantized even when
the longitudinal resistance increases monotonously with the current. Then a
collapse in the quantized resistance occurs while longitudinal resistance keeps
its gradual increase. The exponential increase of the conductivity with respect
to the current suggests impurity mediated inter-Landau level scattering as the
mechanism of the breakdown. The results are interpreted as the strong variation
of the breakdown behavior throughout the sample due to the randomly distributed
scattering centers that mediates the breakdown.
