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