Surface Diffusion and Incorporation Process of Adatom in Fe-Al Multilayer System

Abstract

Using the ab initio pseudopotential calculations, the surface diffusion and incorporation process at the interface of Fe-Al multilayer system were quantitatively investigated. The hollow site was most stable adsorption site on both Al (001) and Fe (001) surface. The adsorption energies were 8.62 eV for Fe/Al (001) and 5.30 eV for Al/Fe (001) system. The calculated energy barriers for the surface diffusion of adatom were 0.89 eV and 0.61 eV for each system. The energy barrier for the incorporation of Fe adatom into the Al substrate was calculated to be 0.38 eV and the energy gain of the system was 0.49 eV. However, the Al adatom required relatively large energy barrier, 0.99 eV for the incorporation into the Fe substrate resulting in 0.13 eV increase in total energy of the system.

Electronic Structures and Magnetism of Al/Fe(001) Thin-Film Systems: First-Principles Calculations

“…2(a)] state, the total energy of the Al n /Fe(001) systems is decreasing with the diffusion depth of Al into Fe(001) substrate and converges. This is due to the bonding energy of Al-Fe 5) and we can predict that the total energy of Al-mixed Fe(001) would keep converging because the surface effect would fade away as Al diffuses deeper. Therefore, the interface-confined Al/ Fe(001) intermixing 6) in previous work results from only the kinetic origin, high diffusion energy barrier, which overwhelms the energetic stability of deeper diffusion of Al into Fe(001).…”

“…1,3) Since the stability of ferromagnetic states of Fe layers is the important factor in the memory applications and is related to the atomic structure at Fe-Al multilayer interfaces, many efforts have been done to characterize the interface Fe-Al phases experimentally and theoretically. [4][5][6] For example, low energy electron diffraction measurement showed that the Al layers are likely to agglomerate on the top surface layer of Al/Fe(001) system and the bcc structure of Fe(001) substrate are kept. 7) A theoretical work on the Fe-Al multilayer system by Kim et al 5) revealed that the different energy barrier for the deposited Al (Fe) incorporation into Fe (Al) surface is the reason for the different surface phase formations in Al/Fe(001) and Fe/Al(001) systems.…”

“…[4][5][6] For example, low energy electron diffraction measurement showed that the Al layers are likely to agglomerate on the top surface layer of Al/Fe(001) system and the bcc structure of Fe(001) substrate are kept. 7) A theoretical work on the Fe-Al multilayer system by Kim et al 5) revealed that the different energy barrier for the deposited Al (Fe) incorporation into Fe (Al) surface is the reason for the different surface phase formations in Al/Fe(001) and Fe/Al(001) systems. On Contrary to the Al-deposited Fe(001) case, Fe-deposited Al(001) substrate formed amorphous.…”

Atomic-Scale Investigation of the Ti/Al(001) Interface: A Molecular Dynamics Simulation

“…In previous studies, two kinetic factors, local acceleration and incorporation energy barrier were introduced to quantitatively analyze the amount of interface intermixing in epitaxially grown metallic multilayers. 3,4,[12][13][14] Local acceleration is the increased kinetic energy of deposited adatoms due to the attractive forces between the adatoms and the substrate atoms. Previous study has suggested that the local acceleration values were the most decisive factor of intermixing amount of the TM/Al(001) system.…”

“…4) In previous studies, the energy barriers for the incorporation of TM adatoms into the Al(001) substrates were calculated using density functional theory (DFT) method. [12][13][14] In this study, the energy barrier for the incorporation of the Ti adatoms into Al(001) substrate was calculated using the molecular statics method, which has been adopted to successfully calculate the energy barriers in metallic thin film systems such as Co/Al(001), Fe/ Cu(111). 4,15) The energy barrier was calculated considering the relaxation of the substrate atoms during the Ti adatom penetration.…”