Graphene mobility on SiO2 is limited to 40,000 cm2/V-s by LA phonon scattering. Suspended graphene, on the other hand, has shown a mobility as high as 200,000 cm2/V-s - but suspended graphene is not directly usable for most electronic applications.  Usually only the best measurements (rather than averages) are reported in the literature for graphene mobility; an average graphene sample, using current techniques of flaking, could have mobilities far lower than the limit imposed by the SiO2 phonons - more like 5,000 to 10,000 cm2/V-s. This is because of impurity scattering that causes extra scattering events and increases the scattering rate.

A group from Penn State and Yale has reported graphene mobility on PZT substrates (Phys. Rev. Letters, April 3). The substrate-limited mobility is 70,000 cm2/V-s at room temperature.  So, if high-quality PZT substrates are easy to make, and if grown graphene layers can be transferred onto PZT substrates, we can expect a 2X improvement in the mobility limit imposed by the substrate.