Atomistic Mechanism of Surfactant-Assisted Epitaxial Growth

Camarero, Julio; Ferrón, J.; Cros, Vincent; Gómez, Liliana; Parga, Amadeo L. Vázquez de; Gallego, José M.; Prieto, J. E.; Miguel, J. J. de; Miranda, Rodolfo

doi:10.1103/physrevlett.81.850

Cited by 127 publications

(89 citation statements)

References 27 publications

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“…This capping monolayer of surfactant atoms forces a layer-by-layer growth mode even for Cu atoms on top of a Co surface. A combined experimental and simulation study 22 has, furthermore, revealed the atomistic mechanism by which the surfactant induces a layer-by-layer growth. This proceeds via suppressing the hopping mechanism of surface diffusion over the terraces and promoting atomic exchange between surfactant and deposited atoms, both at the terraces and across the steps.…”

Section: D332mentioning

confidence: 99%

Influence of Ag Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

Neuróhr

Péter

Pogány

et al. 2015

J. Electrochem. Soc.

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In order to explore the possible surfactant effect of Ag on the formation of electrodeposited multilayers, Co/Cu(Ag) multilayers were prepared by this technique and their structure and giant magnetoresistance (GMR) were investigated. The multilayers were deposited from a perchlorate bath with various amounts of Ag + ions in the solution for incorporating Ag atoms into the multilayer stack. Without Ag addition, secondary neutral mass spectroscopy (SNMS) indicated a well-defined composition modulation of the undermost Co/Cu bilayers. However, already at an Ag content as low as 1.8 at.% incorporated, SNMS showed a deterioration of the periodic multilayer structure. In agreement with the SNMS results, superlattice satellites were visible in the X-ray diffraction (XRD) patterns of the multilayers with up to 0.3 at.% Ag. The satellites were, however, very faint even for multilayers without Ag addition, indicating that the multilayers have high interface roughness and/or poor periodicity. In the absence of Ag and at the smallest Ag content investigated by XRD, a strong central multilayer peak and the weak superlattice satellites were complemented by weak diffraction maxima from non-periodic Co and Cu domains. In the Co/Cu(Ag) multilayer containing about 25 at.% Ag, i.e., nearly as much as Cu, XRD found a separate Ag(Cu) phase. In spite of the imperfect layered structure, a multilayer-type GMR behavior was observed in all samples up to about 10 at.% Ag incorporated in the multilayer stack. The GMR magnitude increased for Ag contents up to about 1 at.%, which implies that a small amount of Ag may have a beneficial effect through a slight modification of the layer growth and/or interface formation. However, for higher Ag contents beyond this level, the GMR was reduced in line with the structural degradation revealed by XRD and SNMS. For the highest Ag contents (above about 10 at.%), the GMR exhibited a behavior characteristic of a granular magnetic alloy, in agreement with the results of the structural study. One of the major obstacles hindering the realization of a high giant magnetoresistance (GMR) in electrodeposited (ED) ferromagnetic/non-magnetic (FM/NM) multilayers is that the nonmagnetic spacer layer cannot be electrodeposited as pinhole-free for layer thicknesses which are required to achieve high GMR and an oscillatory GMR behavior. 1 Sputtered Co/Cu multilayers 2-4 exhibit an oscillatory GMR and a room-temperature GMR of about 50% and 20% at about 1 and 2 nm Cu layer thicknesses, respectively. At these particular spacer thicknesses, a strong antiferromagnetic (AF) exchange coupling exists between the adjacent magnetic layers. It gives rise then to a large GMR effect since the AF coupling ensures an antiparallel alignment of the magnetizations of the neighboring magnetic layers in zero magnetic field. For spacer thicknesses between these so-called AF maxima, the exchange coupling is predominantly ferromagnetic. Thus, due to the parallel alignment of the layer magnetizations even in zero magnetic field, no GMR eff...

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Section: D332mentioning

confidence: 99%

Influence of Ag Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

Neuróhr

Péter

Pogány

et al. 2015

J. Electrochem. Soc.

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“…When Pb is deposited onto Cu(111) at room temperature (RT), the growth mode is of Stranski-Krastanov type [14], i. e. islands start to grow once a wetting layer is complete. These islands are (111)-oriented nanocrystallites with a height distribution that is not statistical.…”

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Local Measurement of the Eliashberg Function of Pb Islands: Enhancement of Electron-Phonon Coupling by Quantum Well States

et al. 2015

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Inelastic tunneling spectroscopy of Pb islands on Cu(111) obtained by scanning tunneling microscopy below 1 K provides a direct access to the local Eliashberg function of the islands with high energy resolution. The Eliashberg function describes the electron-phonon interaction causing conventional superconductivity. The measured Eliashberg function strongly depends on the local thickness of the Pb nanostructures and shows a sharp maximum when quantum well states of the Pb islands come close to the Fermi energy. Ab initio calculations reveal that this is related to enhanced electron-phonon coupling at these thicknesses.

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“…16 In many cases, exchange processes can lead to surfactant-assisted epitaxial growth, since the floating layer can promote epitaxial growth by modifying the diffusion mechanism of the growing layer. 13,17 The place exchange at the level of the monolayer is driven by the difference in the interaction with the Au(111) substrate; while the adsorption energy of exTTF on Au(111) is only of 0.32 eV per molecule, 8 the expected adsorption energy of PCBM is substantially larger, since for C 60 on Au(111) it is of the order of 1.9 eV per molecule. 18 In order to determine the dependence of the exchange process on the thickness of the exTTF layer, we deposited B0.5 ML of PCBM on top of a B2.5 ML-thick film of exTTF (Fig.…”

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An STM study of molecular exchange processes in organic thin film growth

et al. 2014

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The growth of a fullerene derivative (PCBM) on top of a layer of a tetrathiafulvalene (TTF) derivative previously deposited on Au(111) has been studied by scanning tunneling microscopy (STM). The results show that the preferential interaction with the gold substrate induces the exchange of PCBM molecules with the exTTF monolayer, expelling exTTF molecules to the outer surface. This exchange process is forbidden when the thickness of the exTTF layer increases above the monolayer, and the larger surface energy of PCBM leads to the growth of 3D islandsOur work was supported by the MICINN of Spain (FIS2010-18847, FIS2012-33011), Comunidad de Madrid (NanobiomagnetS2009/MAT-1726), CONSOLIDER-INGENIO on Molecular Nanoscience (CSD2007-00010) and European Union (SMALL PITN-GA- 2009-23884

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Atomistic Mechanism of Surfactant-Assisted Epitaxial Growth

Cited by 127 publications

References 27 publications

Influence of Ag Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

Influence of Ag Additive to the Spacer Layer on the Structure and Giant Magnetoresistance of Electrodeposited Co/Cu Multilayers

Local Measurement of the Eliashberg Function of Pb Islands: Enhancement of Electron-Phonon Coupling by Quantum Well States

An STM study of molecular exchange processes in organic thin film growth

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