Long jumps contribution to the adatom diffusion process near the step edge: The case of Ag/Cu(110)

In this work, the diffusion of a single Ag adatom on a low-index Cu surface (110) in the presence of a step edge is studied using the embedded-atom method (EAM). Molecular static simulation is carried out in order to calculate the activation energy of different diffusion processes. Our findings are in a good agreement with results existing in the literature indicating that adatom diffusion via jump process is more favored than the other mechanisms. The activation energy corresponding to diffusing via hopping is found to be 0.25 eV (at 0 K). On the other hand, the activation barrier calculated by molecular dynamics (MD) simulation for a large range of temperature (310–500 K) is found to be around 0.25 eV for both upper and lower position leading to a good agreement between static and dynamic calculations. The prefactor for Ag adatom self-diffusion via hopping on Cu(110) surface near the step edge is examined. The results show that the prefactors are 2.7 and 3.6 × 104 cm2 s−1 for the upper and lower position, respectively. This is in line with the value of 10−3 cm2 s−1 that is generally adopted. We also found that long jumps occur frequently in this system and their contribution cannot be neglected

Energy Barriers For Diffusion On Heterogeneous Stepped Metal Surfaces: Ag/Cu(110)

In this paper we investigated the diffusion of Ag adatom by computing the energy barriers for many elementary diffusive processes which are likely to happen near to the step edge on Cu (110). The barriers are calculated by means of molecular dynamics simulation by using embedded atom potentials. The proximity to steps alters these barriers considerably, and very different results may be expected. In fact, our numerical calculations show that the diffusion via jump process along step edge is predominant for Ag/Cu(110) and the diffusion over the step occurs sometimes, but only via exchange mechanisms. The adatom diffusion across channels is difficult due to the high value of activation energy required (around 1 eV). Furthermore, we found the Ehrlich-Schwoebel barrier for diffusion around 120 meV in order to descend via exchange process and of the order of 170 meV via hopping mode. This aspect may have a strong influence on the growth character. In general our results suggest that, for our metal system, diffusion mechanism may be important for mass transport across the steps. Implications of these findings are discussed. © 2013 Elsevier B.V. All rights reserved

Numerical study of hetero-adsorption and diffusion on (100) and (110) surfaces of Cu, Ag and Au

reserved5siQuenched molecular dynamics simulations and density-functional theory (DFT) calculations are used to study the adatom hetero-diffusion on the (100) and (110) surfaces of four systems: Au/Ag, Ag/Au, Au/Cu, Cu/Au. Atomic interactions are described by embedded-atom method potentials, that are validated by a comparison with DFT results on diffusion barriers. The local relaxation of surface atoms around the adatom is analyzed, together with adsorption energies and hopping diffusion barriers. We find that atomic relaxation is qualitatively different between (100) and (110) surfaces, with the exception of the Au/Cu case. Hopping diffusion barriers are larger on the (100) than on the (110) surface. Many-body and relaxation effects cause significant differences between Ag/Au and Au/Ag barriers, and between Cu/Au and Au/Cu barriers.mixedElkoraychy, E; Sbiaai, K.; Mazroui, M.; Boughaleb, Y.; Ferrando, R.Elkoraychy, E; Sbiaai, K.; Mazroui, M.; Boughaleb, Y.; Ferrando, Riccard

Diffusion Of Ag Dimer On Cu (110) By Dissociation-Reassociation And Concerted Jump Processes

In this work we investigate the diffusion of Ag dimer on Cu(110) surface by molecular dynamics simulation based on semi-empirical many-body potentials derived from the embedded atom method. The dissociation-reassociation process is predicted to be dominant in static regime and this is confirmed by the dynamic investigation. A good agreement is found between static activation barrier and dynamic potential barrier. © 2012 IEEE

Heterodiffusion of Ag adatoms on imperfect Au(1 1 0) surfaces

The hetero-diffusion of Ag adatoms on imperfect Au(1\uc2 1\uc2 0) surfaces is studied using Molecular Dynamics (MD) simulations. The atomic interactions are described by an Embedded Atom Method (EAM) potential. Static activation energies governing various diffusion processes (jumps and exchanges) are calculated by quenched MD, finding that activation energies for interlayer mobility at straight step edges are somewhat larger than those on the flat surface in the cross-channel [1\uc2 0\uc2 0]-direction, while interlayer barriers at kinks are considerably lower. Dynamic activation energies are calculated at high temperature from the Arrhenius plots of different diffusion mechanisms and compared to static barriers

Numerical study of atomic diffusion processes of copper on silver (110) surface: Cu/Ag (110)

peer reviewedThe aim of this paper is to study the diffusion of Cu adatom on Ag (110) by using the molecular dynamics simulation in the framework of the embedded atom method (EAM) as model of atomic interaction. Our simulation results predict that several diffusion processes such as simple jump, long jump and exchange mechanism may occur in the same system. The static barrier is calculated for each process by the drag method. The dynamic activation energy calculated from the Arrhenius law is in a good agreement with the static barrier. The presence of double jump is studied using velocity correlation function showing small contributions in diffusion process. Implications of these findings are discussed in more details

Diffusion processes of trimers on missing row surfaces: Cu3Ag (110) and Ag3 Cu(110)

A semi-empirical potential according to the embedded atom, has been applied to investigate the diffusion of trimers by computing the energy barriers for different mechanisms. Our attention was more focused on the leapfrog process which is likely to occur on missing row surfaces. The activation barriers of this mechanism are calculated using drag method at 0K. These barriers are found to be 0.64 and 0.68 eV for hopping out the channel for Cu3Ag (110) and Ag3 Cu(110) and Ag 3 / Cu (110) respectively. While for hopping down at the other side they are about 0.42 and 0.32 eV. Moreover, a deep metastable position is observed during leapfrog diffusion leading to some spectacular trimer motion. At high temperature and essentially for Cu 3Ag (110) and Ag3 Cu(110), we also observed a competition between leapfrog process and concerted jump mechanism with a deformation of trimer geometry. Implications of these findings are briefly discussed. © 2013 Springer Science+Business Media New York