Lattice-Matched Epitaxial Graphene Grown on Boron Nitride

Lattice-matched graphene on hexagonal boron nitride is expected to lead to the formation of a band gap but requires the formation of highly strained material and has not hitherto been realized. We demonstrate that aligned, lattice-matched graphene can be grown by molecular beam epitaxy using substrate temperatures in the range 1600-1710 degrees C and coexists with a topologically modified moire pattern with regions of strained graphene which have giant moire periods up to similar to 80 nm. Raman spectra reveal narrow red shifted peaks due to isotropic strain, while the giant moire patterns result in complex splitting of Raman peaks due to strain variations across the moire unit cell. The lattice-matched graphene has a lower conductance than both the Frenkel-Kontorova-type domain walls and also the topological defects where they terminate. We relate these results to theoretical models of band gap formation in graphene/boron nitride heterostructures.