  Epitaxial growth of graphene on transition metal substrates is an important
route for obtaining large scale graphene. However, the interaction between
graphene and the substrate often leads to multiple orientations, distorted
graphene band structure, large doping and strong electron-phonon coupling. Here
we report the growth of monolayer graphene with high crystalline quality on
Pt(111) substrate by using a very low concentration of an internal carbon
source with high annealing temperature. The controlled growth leads to
electronically decoupled graphene: it is nearly charge neutral and has
extremely weak electron-phonon coupling (coupling strength $\lambda$ $\approx$
0.056) as revealed by angle-resolved photoemission spectroscopic measurements.
The thermodynamics and kinetics of the carbon diffusion process is investigated
by DFT calculation. Such graphene with negligible graphene-substrate
interaction provides an important platform for fundamental research as well as
device applications when combined with a nondestructive sample transfer
technique.
