  We report scanning tunneling microscopy and spectroscopy investigation of
graphene nanoribbons grown on an array of bunched steps of a 6H-SiC(0001)
substrate. Our scanning tunneling microscopy images of a graphene nanoribbons
on a step terrace feature a (sqrt(3)x sqrt(3))R30{\deg} pattern of aromatic
rings which define our armchair nanoribbons. This is in agreement to a
simulation based on density functional theory. As another signature of the
one-dimensional electronic structure, in the corresponding scanning tunneling
spectroscopy spectra we find well developed, sharp Van Hove singularities.
