Mesoscopic Relaxation in Homoepitaxial Metal Growth

Ov, Lysenko; Vs, Stepanyuk; Hergert, W.; Kirschner, Jessica

doi:10.1103/physrevlett.89.126102

Cited by 87 publications

(64 citation statements)

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“…Although evidenced for a particular system, this result confirms the predictions on mesoscopic relaxation [3,16]. Our results give a clear evidence that the surface-states electrons on nanoislands are significantly affected by local atomic structure.…”

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confidence: 79%

“…Metal islands tend to adopt the lattice parameter of the underlying surface [2], and as a consequence the bond lengths between the metal atoms in the supported nanoisland are different than those in the parent metals, resulting in changes due to strain. A theoretical study on homoepitaxial double layer Cu islands on Cu(111) [3], has shown that the strain produces an inhomogeneous distribution of bond lengths over the nanoisland, the average bond length varying with island size. The nanoislands also locally distort the surface and induce a displacement pattern in the substrate which affects the diffusion of atoms and, ultimately, the growth of the nanoislands.…”

mentioning

confidence: 99%

“…The relaxed atomic configurations have been obtained by means of ab initio fitted many-body potentials formulated in the second moment approximation of the tight-binding theory [3,16,17]. Perfectly triangular unfaulted bilayer Co islands with sizes ranging from 4 nm up to 30 nm were studied.…”

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Size-Dependent Surface States of Strained Cobalt Nanoislands on Cu(111)

et al. 2007

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Low-temperature scanning tunneling spectroscopy over Co nanoislands on Cu(111) showed that the surface states of the islands vary with their size. Occupied states exhibit a sizeable downward energy shift as the island size decreases. The position of the occupied states also significantly changes across the islands. Atomic-scale simulations and ab inito calculations demonstrate that the driving force for the observed shift is related to size-dependent mesoscopic relaxations in the nanoislands.PACS numbers: 73.20.At, It was recognized quite early that metallic particles exhibit unique properties that differ significantly from their bulk counterparts [1]. Nanoislands grown on metal surfaces, in particular, have been a matter of intense research for decades in view of prospective applications in a vast variety of domains ranging from magnetoelectronics, catalysis, optoelectronics, to data storage technology. The electronic, magnetic and chemical properties of a nanoisland are governed by the size, shape and structure of the island. These, in turn, are profoundly influenced by the lattice mismatch with the metal substrate and, for heteroepitaxial systems, also by the bonding interactions in the island/substrate interface (ligand effects). Metal islands tend to adopt the lattice parameter of the underlying surface [2], and as a consequence the bond lengths between the metal atoms in the supported nanoisland are different than those in the parent metals, resulting in changes due to strain. A theoretical study on homoepitaxial double layer Cu islands on Cu(111) [3], has shown that the strain produces an inhomogeneous distribution of bond lengths over the nanoisland, the average bond length varying with island size. The nanoislands also locally distort the surface and induce a displacement pattern in the substrate which affects the diffusion of atoms and, ultimately, the growth of the nanoislands.Despite these studies, our knowledge of how strain affects the properties of a metallic nanoisland, especially the electronic states, remains very limited. The fundamental problem of the change in energy upon lattice distortion in solids has first been addressed by J. Friedel within a simple model [4], and latter on extended to various problems of lattice contractions at metal surfaces and clusters [5]. On the same lines, it has been shown for thin films that strain effects, along with ligand effects, can cause a shift of the surface d band [6,7,8], resulting in chemical properties that are significantly different from those of the pure overlayer metal. Recently, a modification of electronic states due to a local strain field induced by a nanopattern formation has been observed for Cu(100) covered with N atoms [9].In this Letter, we specifically focus on the interplay between strain-induced structural relaxations and the surface states of Co nanoislands on Cu(111). These nanoislands constitute a reference system that has been extensively investigated by Scanning Tunneling Microscopy/Spectroscopy (STM/STS) [10,11,12,13,14]. By ...

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Size-Dependent Surface States of Strained Cobalt Nanoislands on Cu(111)

et al. 2007

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“…Recently, more subtle overlayer-induced effects have been investigated. For example, studies of overlayer mesoscopic islands show that an island can induce substantial elastic strain in the surrounding substrate atoms [37][38][39]. These island-induced strains can influence adatom diffusion [40,41], which can subsequently impact island growth and morphology.…”

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confidence: 99%

Core-level spectroscopy of the Pd/W(110) interface: Evidence of long-range Pd-island–W interactions at submonolayer Pd coverages

et al. 2009

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We have measured W 4f 7/2 core-level photoemission spectra from W(110) in the presence of Pd overlayers for coverages up to ∼1 pseudomorphic monolayer (ML). At coverages close to 0.05 ML a striking change in the W core-level spectrum is observed, which we interpret as indicating a long-range lateral effect of 2D Pd islands upon the W electronic structure in both the first and second W layers. As the coverage increases the long-range effect weakens and finally vanishes near 0.85 ML. Above this coverage the W spectra are typical for a W-based bimetallic interface, with the first-layer W atoms exhibiting a small interfacial core-level shift (−95 ± 5 meV) compared to the bulk atoms.

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“…Even with this simple model the obtained strength is of the order of the experimental data. We note that Stepanyuk et al [26,27] have calculated in-plane (and out-of-plane) relaxation of lattice parameters near the edges of two-dimensional close packed adatom islands. In-plane contractions in the order of also 1% have been obtained, the actual value being dependent on the size of the islands.…”

Section: Volume 93 Number 8 P H Y S I C a L R E V I E W L E T T E R mentioning

confidence: 99%

Novel Local Free Energy Minimum on the Cu(001) Surface

et al. 2004

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High-resolution LEED (low-energy electron diffraction) data of Cu(001) reveal an uniaxial in-plane lattice reconstruction by 1%. One-dimensional nanogrooves induced by ion bombardment involve the creation of steps that enable this reconstruction. This is the first verification of van der Merwe's prediction of step facilitated reconstruction. We confirm the predicted dependence on step orientation: h100i steps allow stress-relief and h110i steps do not, consistent with the known elastic anisotropy. Similar behavior is predicted for other nonreconstructed (001) (001)-surfaces of transition and noble metals do reconstruct. Their termination is a (111)-like overlayer that periodically matches the (001)-bulk structure. The decision whether the (001)-surface does reconstruct or not is quite subtle. The adsorption of small amounts of atoms or molecules can lead to deconstruction [5,6]. In an ab initio density-functional-theory study, Fiorentini et al. [7,8] investigated the tendency for (001)-transition metal surfaces to reconstruct. They find that surfaces of the metals at the end of the 5d transition series such as Ir, Pt, and Au reconstruct, whereas their 4d counterparts Rh, Pd, and Ag do not. Reconstruction requires bond rearrangements, leading to significant energy losses due to the disruption or stretching of bonds between the mismatched layer and that underneath. The reconstruction results from a delicate balance between surface-substrate mismatch and strain related energy gain [7,8]. Their high strain energy favors reconstruction for the 5d (001)-surfaces, while it is too small for their 4d and 3d counterparts. The surfaces of the 3d and 4d metals remain unreconstructed in agreement with experimental observations. The claim by Müller et al. [9] of an in-plane reconstruction of clean Cu(001) created a sensation. They found a contraction of about 1% from their LEED (low-energy electron diffraction) I-V-analysis. Their finding provided a nice framework for the contraction of 1% found for the pseudomorphic growth of Fe/Cu(001) [10 -12]. The Cu(001) in-plane reconstruction was challenged both experimentally [13,14] and theoretically [15]. Müller et al. [16] conceded and attributed their findings to either a ''lower lateral crystallinity'' of their surface or ''systematic errors affecting the accuracy of their analysis.'' In a later LEED-I-V-study, Walter et al.[17] indeed obtained smaller in-plane relaxation by introducing an energy dependent inner potential.We find experimental evidence for a new local minimum in the free energy of Cu(001). Indeed, Cu(001) has a strong tendency for an in-plane lattice contraction of 1%. It only prevails on surfaces with a finite amount of steps, when oriented along the h100i-azimuth. Note that h100i is the soft direction with respect to deformation [18]. This geometry permits to relieve tensile stress. This result is of general importance to the 3d and 4d (001)-metal surfaces with implications for the creation of nanostructures on or in these surfaces and the structure of hetero...

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Mesoscopic Relaxation in Homoepitaxial Metal Growth

Cited by 87 publications

References 24 publications

Size-Dependent Surface States of Strained Cobalt Nanoislands on Cu(111)

Size-Dependent Surface States of Strained Cobalt Nanoislands on Cu(111)

Core-level spectroscopy of the Pd/W(110) interface: Evidence of long-range Pd-island–W interactions at submonolayer Pd coverages

Novel Local Free Energy Minimum on the Cu(001) Surface

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