Molecular Dynamics Simulation Of Cu Clusters Deposition On A Fe(001)Surface

The Fe/Cu magnetic multilayer film consisting of ferromagnetic Fe layers and non-ferromagnetic Cu layers for giant magnetoresistance could be applied in read head for high density magnetic recording, magnetoresistance sensors and magnetic random access memory, etc. So studies of Fe/Cu magnetic multilayers are always one of the forefronts and hot spots for the research of materials science. The structure has formed in the process of preparation of thin-films, the performance of thin-films is decided by the structure of thin-films. People have done a lot of work to investigate the relationship between structure and the giant magnetoresistance of the Fe/Cu magnetic multilayer films, but the research about the structure formation of Fe/Cu magnetic multilayer film have less been presented. This is largely due to that the limitation of experimental conditions and technologies cannot observe the formation process of thin-films. However, the method of molecular dynamics can simulate the microprocess of thin-film growing and reveal the evolution law of thin-film at atomic level. The cluster which can seriously affect the quality of thin-film exists in the vapor-phase of some preparing techniques of Fe/Cu magnetic multilayer film. Therefore, this paper reveals the microprocess of Cu clusters deposition on a Fe(001) surface by molecular dynamics simulation, explores the micromechanism of interaction between clusters and the substrate surface, and analyzes the effect of different conditions on the results of cluster deposition.The software package applied in the molecular dynamics simulation of cluster deposition was developed, in view of the molecular dynamics simulation of Cu clusters deposition on a Fe (001) surface. The program in the software package, which compiles by the Fortran95language, is correct and has a high computational efficiency through the debugging and verifying. In this way, it does not confine to the limitation of programs in existing software or script, and the corresponding subroutine can be alter according to the actual needs of the research object. In the meanwhile, it can lay a solid foundation for compiling the molecular dynamics simulation program of film-forming by cluster deposition in the next step.After the investigate and survey of a series of interatomic potentials in metals, the many-body interatomic potential developed by Ackland in the Finnis-Sinclair formalism is employed to describe the atomic interactions, which take place in our models, such as, Cu-Cu, Fe-Fe and Cu-Fe interactions. The three clusters, Cu13, Cu55and Cu147, which all have the regular icosahedron configuration, were selected as the deposited clusters, and the initial incident energies of clusters range from0.0to30.0eV/atom. The molecular dynamics simulations of the cluster soft landing deposition, the cluster with initial incident energies ranging from0.1to10.0eV/atom deposition, and the cluster with initial incident energies ranging from10.0to30.0eV/atom deposition have been carried out according to the deposited characteristics of cluster with different incident energies. In the events of the cluster soft landing deposition, the temperature of substrates are0,300and800K, beyond that, the temperatures of substrate are set as300and800K in all of other energetic cluster deposition events.The main conclusions obtained by molecular dynamics simulation of Cu clusters deposition on a Fe(001) surface in this paper are as follows:1. The features of the interaction between the cluster and the solid surface are far different than that of single-atom-solid-surface interactions. In the former case the collective collisions of cluster play a dominant role. The energy transformation between cluster and substrate, the rearrangement of cluster atoms and the damage of the substrate surface due to the cluster impacting also are completed by the collective collisions of cluster.2. The collective effect of cluster are reflected in the process of the energy transformation between cluster and substrate, the rearrangement of cluster atoms and the damage of the substrate surface due to the cluster impacting.3. The initial incident energy which decides the characteristics of cluster deposition has a threshold value. When the initial incident energy of cluster is relatively low, the cluster mainly reconstructs above the substrate surface, the cluster begins to exhibit the penetrating characteristic with the increase of initial incident energy of cluster, as the initial incident energy of cluster increases further, the cluster starts to produce defects and the crater forms in the substrate surface. Moreover, the threshold value is slightly affected by the cluster size and the substrate temperature also.4. The initial incident energy of cluster rather than the cluster size and the substrate temperature mainly influences the diffusion of cluster atoms.5. The epitaxial degree of the small cluster is higher than the large cluster. When the epitaxial degree of the cluster is low, it has a noticeable increase with the initial incident energy of cluster increasing or with the temperature of substrate elevating. However, the effect of increasing initial incident energy of cluster or elevating of temperature of substrate on the epitaxial of cluster is unobvious as the epitaxial degree of the cluster is high.6. The degree of bonding between cluster and substrate increases with the incident energy of cluster increasing. Compared with large cluster, the small cluster more closely combines with the substrate. When other conditions of cluster deposition are same, the intensity of cluster combining with substrate strengthens as the temperature of substrate elevates.7. The final morphology of cluster deposition is also affected by the initial incident energy of cluster, the cluster size and the temperature of substrate.