Theoretical study of the heteroepitaxial growth of Pd on Cu(111), Pd on Ni(111), Ni on Pd(111), and Cu on Pd(111) using a semiempirical method

Abstract

Heteroepitaxy has been widely studied by many different theoretical and experimental techniques. Each technique focuses on some features of the growth process, and only by combining the information each provides a full characterization can be given. In this work, the growth of Pd on Ni(111), Pd on Cu(111), Cu on Pd(111), and Ni on Pd(111) is studied with a purely energetic approach which consists of determining a unit cell with a size that depends on the relation between the lateral misfit of the deposited film and the substrate. The energetic is evaluated using a semiempirical coupled with a genetic algorithm global search method to determine with accuracy the relaxation magnitudes of the system. With this approach, features such as interlayer spacings, variation in the film's lattice parameter with coverage, and diffusion influence in the growth process are studied qualitative and quantitatively. The results obtained are directly compared with experimental findings from literature and also presented in this work. The theory-experiment comparison shows that the methodology used is successful in describing qualitatively most features of all four systems. However, for the Pd on Cu(111) case, poor agreement is found, and the analysis of the influence of diffusion and temperature suggests that a somewhat complex alloy formation in the interface is expected for this particular system.