In the present paper the molecular dynamics method with the use of multiparticle potentials calculated within the limits of the embedded atom method has been used to investigate the orientational dependence of the Ni film growth mechanism on Pd of (001), (110) and (111) orientations, the conjugation nature on the interphase boundary and the component distribution in the film. The Pd substrates were simulated in the form of calculated cells containing 8 planes with 900 atoms in each plane. The molecular dynamics deposition process of Ni consists in sequential deposition of 0.1 monolayer (ML) of randomly distributed Ni atoms on the Pd substrate surface every 3•10-11 s.
Following each deposition the static relaxation of the system was performed. Then the Ni and Pd atoms were given the initial rates according to the Maxell distribution at 1000 K, and the isothermal annealings of the heterosystem were made.
It has been shown that during the growth of Ni film on the singular surfaces of (001) and (110)Pd the following heterostructures are formed: Pd – single-layer epitaxially stabilized solid solution phase – solid solution film, the latter smoothly transforming to the Ni film.
The formation of this heterostructure ensures the two-stage elastic accommodation of the critical value misfit at the initial stages of the film growth.
With the increase of the average thickness of the film the elastic strain relaxation takes place, namely, in the heterosystem Pd-Ni (001) by the misfit dislocations, in the heterosystem Pd-Ni (110) in the [1-10] direction by the misfit dislocations and point defects and in the [001] direction by the partial dislocations. With this the anisotropy of the film deformation is retained. The surface of the growth front on the (110) surface is more developed. During the growth if Ni film on the singular surface of Pd (111) the mixing of the components does not occur. At the initial stages of the island-clusters are not deformed, i.e. the conjugation on the interphase boundary is non-coherent.
The growth in the heterosystem Pd-Ni (111) may be referred to the Folmer-Weber growth mechanism.
The work was performed under the grant of the President of Russian Federation "Support of the Leading Scientific Schools", No. SS-7098.2006.3. |