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 (8x8) silicon nitride was prepared on the atomically clean Si surface under ammonia flux. Then AlN was formed by deposition of Al atoms onto the (8x8) 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 (4x4) 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.