Abstract
The modified embedded atom method (MEAM), an empirical extension of the embedded atom method (EAM) that includes angular forces, has been used to examine the interface between a silicon substrate and a thin overlayer of nickel. A brief review of the MEAM is given and parameters are determined for the Si-Ni system. As verification of the reliability of the model, the geometry, energy and elastic constants of a number of ideal Si-Ni compounds are calculated and are found to agree reasonably well with experiment and first-principles calculations. Planar defect energies are also presented. Calculations of the relaxed energy and geometry of a coherent 10 AA overlayer of Ni on Si(001) yield two similar structures, both of which were typified by a slightly rippled Ni structure relative to perfect FCC Ni. The lower-energy interface also contained rows of slightly shifted Ni atoms. It is found that significant differences occur between the energetics of a rigid or relaxed separation of the overlayer. Separation of the overlayer with a monolayer of Si atoms attached to the Ni yields a significantly lower-energy structure than separation exactly at the interface. The relaxed brittle fracture energy of this interface is found to be 1.5 J m-2, which is significantly lower than the unrelaxed fracture energy of 4.8 J m-2.
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