  We study the growth and microscopic structure of large-area graphene
monolayers, grown on copper single crystals by chemical vapor deposition (CVD)
in ultra-high vacuum (UHV). Using atomic-resolution scanning tunneling
microscopy (STM), we find that graphene grows primarily in registry with the
underlying copper lattice for both Cu(111) and Cu(100). The graphene has a
hexagonal superstructure on Cu(111) with a significant electronic component,
whereas it has a linear superstructure on Cu(100). The film quality is limited
by grain boundaries, and the best growth is obtained on the Cu(111) surface.
