  Large-area bilayer graphene (BG) is grown epitaxially on Ru(0001) surface and
characterized by low temperature scanning tunneling microscopy. The lattice of
the bottom layer of BG is stretched by 1.2%, while strain is absent from the
top layer. The lattice mismatch between the two layers leads to the formation
of a moire pattern with a periodicity of ~21.5 nm and a mixture of AA- and
AB-stacking. The root3 x root3 superstructure around atomic defects is
attributed to the inter-valley scattering of the delocalized pi-electrons,
demonstrating that the as-grown BG behaves like intrinsic free-standing
graphene.
