The effect of deposition velocity and cluster size on thin film growth by Cu cluster deposition

The deposition of Cu clusters on a Si (0 0 1) substrate was studied using molecular dynamics simulations. EAM, SW and LJ potentials were used to describe the interaction between cluster atoms, substrate atoms, and the cluster–substrate interaction, respectively. Three cluster sizes comprised of 13, 55 and 147 atoms were deposited with various initial velocities (100, 500, 1000, 1500 and 3000 m/s). Results indicated that the degree of epitaxy and film flatness generally increased with the deposition velocity in a certain window. We found that Cu13 cluster at 1500 m/s, Cu55 at 1000 m/s and Cu147 at 500 m/s produced more flat epitaxial layers that matched well with the substrate surface. The flat morphology was much desired for the secondary cluster deposition. The epitaxial degree of a small cluster was higher than that of a large cluster at lower and higher velocities, while at moderate velocities a large cluster showed higher degree of epitaxy. The effect of cluster velocity on the height of mass center of the cluster was also identified.