Low Partial Pressure Chemical Vapor Deposition of Graphene on Copper

A systematic study of the Cu-catalyzed chemical vapor deposition of graphene under extremely low partial pressure is carried out. A carbon precursor supply of just
$\it P$
$\bf_{CH_4}$
$\sim$
0.009 mbar during the deposition favors the formation of large-area uniform monolayer graphene verified by Raman spectra. A diluted
$\bf HNO_3$
solution is used to remove Cu before transferring graphene onto SiO
$_2$
/Si substrates or carbon grids. The graphene can be made suspended over a
$\sim$
12
$\mu$
m distance, indicating its good mechanical properties. Electron transport measurements show the graphene sheet resistance of
$\sim$
0.6
${\bf k\Omega} /\square$
at zero gate voltage. The mobilities of electrons and holes are
$\sim$
1800 cm
$^2$
/Vs at 4.2 K and
$\sim$
1200 cm
$^2$
/Vs at room temperature.