2D AlN layer formation on (111)Si surface by ammonia MBE

An (0001)AlN ultrathin layer formation in ammonia MBE conditions have been investigated by RHEED. Two steps procedure was used: at first, well ordered (8×8) silicon nitride was prepared on the atomically clean Si surface under ammonia flux. Then AlN was formed by deposition of Al atoms onto the (8×8) surface. Temperature dependence of the AlN formation rate was obtained and desorption energy (E_des=2.1 eV) of Al atoms from the surface was estimated. For the first time the (4×4) superstructure of AlN on the (111)Si surface was observed by RHEED. Precise measurements of the AlN in-plain lattice parameter evolution during the initial stages of the AlN formation were carried out. The lattice constant of 3.08 A is found in good agreement with ab initio calculations for a graphene-like AlN.