  Graphene grown via chemical vapour deposition (CVD) on copper foil has
emerged as a high-quality, scalable material, that can be easily integrated on
technologically relevant platforms to develop promising applications in the
fields of optoelectronics and photonics. Most of these applications require
low-contaminated high-mobility graphene (i.e., approaching 10 000 $cm^2 V^{-1}
s^{-1}$) at room temperature) to reduce device losses and implement compact
device design. To date, these mobility values are only obtained when suspending
or encapsulating graphene. Here, we demonstrate a rapid, facile, and scalable
cleaning process, that yields high-mobility graphene directly on the most
common technologically relevant substrate: silicon dioxide on silicon
(SiO$_2$/Si). Atomic force microscopy (AFM) and spatially-resolved X-ray
photoelectron spectroscopy (XPS) demonstrate that this approach is instrumental
to rapidly eliminate most of the polymeric residues which remain on graphene
after transfer and fabrication and that have adverse effects on its electrical
properties. Raman measurements show a significant reduction of graphene doping
and strain. Transport measurements of 50 Hall bars (HBs) yield hole mobility
${\mu}_h$ up to 9000 $cm^2 V^{-1} s^{-1}$ and electron mobility ${\mu}_e$ up to
8000 $cm^2 V^{-1} s^{-1}$, with average values ${\mu}_h$ 7500 $cm^2 V^{-1}
s^{-1}$ and ${\mu}_e$ 6300 $cm^2 V^{-1} s^{-1}$. The carrier mobility of
ultraclean graphene reach values nearly double of that measured in graphene HBs
processed with acetone cleaning, which is the method widely adopted in the
field. Notably, these mobility values are obtained over large-scale and without
encapsulation, thus paving the way to the adoption of graphene in
optoelectronics and photonics.
