  Graphene is a fascinating material for exploring fundamental science
questions as well as a potential building block for novel electronic
applications. In order to realize the full potential of this material the
fabrication techniques of graphene devices, still in their infancy, need to be
refined to better isolate the graphene layer from the environment. We present
results from a study on the influence of extrinsic factors on the quality of
graphene devices including material defects, lithography, doping by metallic
leads and the substrate. The main finding is that trapped Coulomb scatterers
associated with the substrate are the primary factor reducing the quality of
graphene devices. A fabrication scheme is proposed to produce high quality
graphene devices dependably and reproducibly. In these devices, the transport
properties approach theoretical predictions of ballistic transport.
