First, a periodic array of monoatomic surface steps are created on {TAIL ~ the surface} of the substrate at {HEAD ~ an area} to have the superlattice structure grown thereon 
First , a periodic array of monoatomic surface steps are created on { TAIL ~ the surface } of the substrate at { HEAD ~ an area } to have the superlattice structure grown thereon
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH