Heterogeneous and Homogeneous Nucleation in the Synthesis of Quasi-One-Dimensional Periodic Core-Shell Nanostructures

We have analyzed the physical mechanisms responsible for the formation of an ordered sequence of nanoclusters synthesized on a nanowire in the diffusion mode of deposition of free atoms. The results were obtained using a kinetic Monte Carlo model, which takes into account only the interaction between the nearest atoms of the crystal lattice. Nevertheless, this model describes the correlations between the elements of the system at distances significantly exceeding their sizes. We show that the long-range spatial correlation between the synthesized clusters is due to two factors: first, the surface diffusion in the metastable system of deposited atoms which leads to the formation of primary nuclei, and second, the shadow effect arising when growing nanoclusters become rather large. It is these processes that are the "tools" through which individual clusters suppress the development of their neighboring nuclei in the competition for survival and form high self-ordering at the final stage of synthesis. Numerical experiments were carried out for one-dimensional systems with a diamond-like lattice structure. The features of manifestation of self-ordering effects are investigated in detail depending on the orientation of the basic nanowire, temperature, and the rate of supply of free atoms into the system. The observed variety of morphologies of one-dimensional systems at the final stage of synthesis is in good agreement with numerous experimental data obtained during the synthesis of nanoclusters on silicon and germanium nanowires. On the basis of the obtained results, optimal synthesis modes are proposed for increasing the regularity in the localization of synthesized nanoclusters.