Atomic-scale self-organization of Co nanostructures embedded into Cu(100)

We present our experimental and theoretical study on Co diffusion in the first few atomic layers of Cu(001). While the diffusion of Co atoms in Cu(001) is usually expected to be intense at a temperature T 800 K, in the vicinity of the surface, it is already activated at a considerably lower temperature T ∼ 650 K whereas the diffusion in the deep bulk region is still inhibited. This intense near-surface diffusion provides an accumulation of Co atoms in the first six atomic layers upon a single stage Co deposition. The details of the near-surface diffusion are studied by analyzing the distribution of the location depth of the buried single Co atoms. The depth of location of single Co atoms is deduced from scanning tunneling microscopy (STM) data. The subsurface Co atoms induce a perturbation of the electron density of states of the surface which is observable as apparent ringlike ripples in the STM images of the atomically flat Cu surface. The depth of location of the buried Co atoms is determined from the diameter of those rings. The largest amount of Co atoms is found to be in the third layer, emphasizing that the near-surface diffusion should be described by diffusion parameters different from those for bulk diffusion. A model that describes the embedding process of Co atoms into Cu(001) layers is developed. The model assumes Co atoms to diffuse via the vacancy and ring-exchange mechanisms. The energy barriers for the interlayer Co diffusion via those mechanisms are calculated using the nudged elastic band method. The model satisfactorily explains the experimental results. Our study reveals that the energy barriers for Co diffusion in the first five atomic layers of Cu(001) are lower than those in the bulk. This defines the region in which Co diffusion should be considered as a near-surface one.

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“…[45]. The reliability of the potentials for the case of Co atoms embedded in Cu(001) has been demonstrated in previous works [50][51][52].…”

Section: B Calculation Methodsmentioning

confidence: 60%

“…This formulation has been demonstrated to be well applicable for the Co-Cu system [45,46,[49][50][51][52]. The attractive term (the band energy), E i B , contains the many-body interaction.…”

Section: B Calculation Methodsmentioning

confidence: 99%

Co diffusion in the near-surface region of Cu

et al. 2016

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“…At the same time, we employ the MD method for the calculation of barriers of diffusion events. This approach is widely used for the simulation of atomic diffusion and self-organization of different nanostructures on surfaces [23][24][25][26][27]. Strangely enough, any applications of the kMC method to the formation of nanocontacts are unknown to authors.…”

mentioning

confidence: 99%

Formation of gold nanocontacts in an ultrahigh vacuum transmission electron microscope: A kinetic Monte Carlo simulation

Колесников

Kolesnikova

Klavsyuk

et al. 2013

EPL

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The effective method for the simulation of self-organization of metal nanocontacts produced in an ultrahigh vacuum transmission electron microscope has been designed. In the framework of this method the main stages of nanocontact formation have been determined. The basic diffusion events which are responsible for the shape of nanocontacts and the time of their formation have been outlined. The self-organization of nanocontacts with different orientation relative to the base fcc lattice has been studied. The results of our simulations are in a good agreement with experimental data.

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