Fuhrer and co-workers showed that although the room temperature limit of mobility in graphene is as high as 200,000 cm2/Vs, in present-day samples the actual mobility is lower, around 10,000 cm2/Vs, leaving significant room for improvement. Because graphene is only one atom thick, current samples must sit on a substrate, in this case silicon dioxide.
Trapped electrical charges in the silicon dioxide (a sort of atomic-scale dirt) can affect the electrons in graphene and reduce the mobility. Also, vibrations of the silicon dioxide atoms themselves can also have an effect on the graphene which is stronger than the effect of graphenes own atomic vibrations. This so-called remote interfacial phonon scattering effect is only a small correction to the mobility in a silicon transistor, but because the phonons in graphene itself are so ineffective at scattering electrons, this effect becomes very important in graphene.
We believe that this work points out the importance of these extrinsic effects, and creates a roadmap for finding better substrates for future graphene devices in order to reduce the effects of charged impurity scattering and remote interfacial phonon scattering. Fuhrer said.
|Contact: Lee Tune|
University of Maryland