In-plane lattice spacing oscillatory behaviour during the two-dimensional hetero- and homoepitaxy of metals

The present paper is devoted to the analysis of in-plane lattice spacing os cillations (IPLSOs) during two-dimensional hetero- and homoepitaxial growth on (001) surfaces of cubic metals using reflection high-energy electron di ffraction (RHEED). Our aim was to check systematically the agreement betwee n experimental results and theoretical predictions. We have selected the mo st significant heteroepitaxial systems BIA with a misfit positive (V/Fe, Mn /Fe), negative (Ni/Fe, Ni/V, Co/Cu) or close to zero (Fe/Cu, Co/Ni). The ph ase relationships between the different oscillating physical parameters [RH EED intensity, full-width at half maximum (FWHM) of diffraction streaks and in-plane lattice spacing] are examined, as well as the azimuthal dependenc e of the elastic relaxation process. A general good agreement between exper imental data and theory was observed. However, for some systems (Ni/Fe, V/F e), we prove a strong anisotropy of the phenomenon along the [10] and [11] azimuths of the square surface lattice. We also focus on the case of homoep itaxial growth and search for a convincing demonstration of IPLSOs in this specific case. The influence of substrate temperature and azimuthal dependa nce are also investigated. Surprisingly, very large relaxation effects are observed and seem to be correlated to the occurrence of surface reconstruct ion and/or surface contamination. Finally, an anisotropic character was aga in observed on V and Nb (001) surfaces. The morphology of the two-dimension al islands during growth or/and anisotropic surface reconstructions could e xplain such anisotropy. (C) 2000 Elsevier Science B.V. All rights reserved.