GROWTH OF MOSE2 THIN-FILMS WITH VANDERWAALS EPITAXY

The concept of Van der Waals epitaxy that has been recently introduced removes severe lattice matching requirement by using materials which only have strong bonding in two dimensions. We demonstrate that an epilayer of MoSe2 deposited on various substrates can produce films of high crystalline quality despite of large mismatch. RHEED oscillation, observed in-situ for growing MoSe2 epilayers, shows a layer-by-layer growth with evidence for for bilayer type growth, from which the 2H(b) polytype is determined. STM provides real space images of the morphology of the epilayer, and shows novel structures resulting from the large lattice mismatch where the epilayer atoms are commensurated.