  Nanoscale ridges in epitaxial multilayer graphene grown on the silicon face
of 4 degree off-cut 4H-SiC (0001) were found using scanning tunneling
microscopy (STM). These nano-ridges are only 0.1 nm high and 25-50 nm wide,
making them much smaller than previously reported ridges. Atomic-resolution STM
was performed near and on top of the nano-ridges using a dual scanning
technique in which forward and reverse images are simultaneously recorded. An
apparent 100% enlarged graphene lattice constant is observed along the leading
edge of the image for both directions. Horizontal movement of the graphene, due
to both an electrostatic attraction to the STM tip and weak bonding to the
substrate, is thought to contribute to the results.
