Ultrahigh Doping of Graphene Using Flame-Deposited MoO3

The expected high performance of graphene-based electronics is often hindered by lack of adequate doping, which causes low carrier density and large sheet resistance. Many reported graphene doping schemes also suffer from instability or incompatibility with existing semiconductor processing. Here we report ultrahigh and stable
${p}$
-type doping up to
$\sim 7\times 10 ^{13}$
cm
⁻²
(
$\sim 2\times 10 ^{21}$
cm
⁻³
) of monolayer graphene grown by chemical vapor deposition. This is achieved by direct polycrystalline MoO
₃
growth on graphene using a rapid flame synthesis technique. With this approach, the metal-graphene contact resistance for holes is reduced to
$\sim 200~\Omega \cdot \mu \text{m}$
. We also demonstrate that flame-deposited MoO
₃
provides over
$5\times $
higher doping of graphene, as well as superior thermal and long-term stability, compared to electron-beam deposited MoO
₃
.