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BCPs (4, 5, 8, 9). However, even though the self-
assembly of BCPs can correct errors in the pat-
terns, perfect ordering over large areas has not yet
been achieved. Nanoimprint lithography (10, 11),
on the other hand, is a parallel patterning process
but requires a perfect master to replicate. We show
that most of these limitations can be overcome by
capitalizing on a well-established surface reconstruc-
tion of commercially available single-crystalline
wafers to generate nanoscopic surface facets that
can guide the self-assembly of BCPs into a highly
ordered, single-grain array of nanoscopic elements
with a well-defined orientation over large areas.
Large, defect-free single-crystalline wafers,
such as silicon or sapphire, with a well-defined
orientation of the crystal lattice are commercially
available (12–14). By the cutting of single crys-
tals along specific crystallographic planes, unstable
surfaces can be produced that, upon heating, re-
construct, generating crystal facets that form a saw-
tooth topography, where the orientation of the
ridges formed by the sawtooth persists over the
entire surface (13, 14). Sapphire (a-Al2O3), cut
along the ð1010Þ orMplane,isusedasanexam-
ple, although the concept applies to other single-
crystalline materials. The surface reconstruction
is shown schematically in Fig. 1 along with atomic
force microscopy (AFM) images of a freshly cut
and a faceted sapphire surface (13, 14). Initially
the surface is featureless. Upon annealing, the
surface reconstructs and crystalline facets form a
sawtooth pattern on the surface. With the sapphire