Graphene-like AlN layer formation on (111)Si surface by ammonia molecular beam epitaxy

• The highly ordered SiN-(8×8) structure were prepared on a (111)Si surface.
• AlN layer was formed by the deposition of Al onto SiN-(8×8) surface.
• A new (4×4) structure on the (111)Si surface was observed.
• The AlN lattice constant of 3.08Å in agreement with graphene-like AlN was found.

The formation of a graphene-like AlN (g-AlN) layer on a (111)-oriented silicon substrate in ammonia molecular beam epitaxy (MBE) has been investigated by the RHEED method. A flat AlN layer with a thickness of a few monolayers was formed by the deposition of Al atoms onto a highly ordered SiN-(8×8) surface prepared on the atomically flat (111)Si substrate under an ammonia flux. An unusual (4×4) structure of g-AlN on the Si surface was found. The exact coincidence of the fundamental (0 1) AlN streak and the fractional-order (0 5/4) beam of the (4×4) RHEED structure allows us to measure precisely the in-plane lattice parameters of g-AlN. The g-AlN lattice constant of 3.08 Å is found in a good agreement with the ab initio calculations performed recently. The evolution of the g-AlN in-plane lattice constant during the initial stages of the g-AlN formation and transformation to the bulk wurtzite AlN was analyzed.