Iridium on Cu(100): Surface Segregation and Alloying

Gilarowski, G.; Niehus, Horst

doi:10.1002/(sici)1521-396x(199905)173:1<159::aid-pssa159>3.0.co;2-c

Cited by 12 publications

(5 citation statements)

References 12 publications

(7 reference statements)

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“…Although the GPC and ND changed with the different ALD processes, the Ir coatings always exhibited island growth. Other studies on the deposition of Ir by ALD [23,26,56,57], chemical vapor deposition [58,59], evaporation [60,61], or a facile one-pot solvothermal method [62] show comparable results. However, these studies were performed with relatively thick Ir layers, with SEM images providing reliable information for several tens of ALD cycles.…”

Section: Discussionmentioning

confidence: 87%

Influence of Substrate Materials on Nucleation and Properties of Iridium Thin Films Grown by ALD

et al. 2021

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Ultra-thin metallic films are widely applied in optics and microelectronics. However, their properties differ significantly from the bulk material and depend on the substrate material. The nucleation, film growth, and layer properties of atomic layer deposited (ALD) iridium thin films are evaluated on silicon wafers, BK7, fused silica, SiO2, TiO2, Ta2O5, Al2O3, HfO2, Ru, Cr, Mo, and graphite to understand the influence of various substrate materials. This comprehensive study was carried out using scanning electron and atomic force microscopy, X-ray reflectivity and diffraction, four-point probe resistivity and contact angle measurements, tape tests, and Auger electron spectroscopy. Within few ALD cycles, iridium islands occur on all substrates. Nevertheless, their size, shape, and distribution depend on the substrate. Ultra-thin (almost) closed Ir layers grow on a Ta2O5 seed layer after 100 cycles corresponding to about 5 nm film thickness. In contrast, the growth on Al2O3 and HfO2 is strongly inhibited. The iridium growth on silicon wafers is overall linear. On BK7, fused silica, SiO2, TiO2, Ta2O5, Ru, Cr, and graphite, three different growth regimes are distinguishable. The surface free energy of the substrates correlates with their iridium nucleation delay. Our work, therefore, demonstrates that substrates can significantly tailor the properties of ultra-thin films.

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Section: Discussionmentioning

confidence: 87%

Influence of Substrate Materials on Nucleation and Properties of Iridium Thin Films Grown by ALD

et al. 2021

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“…The question we want to address here is in how far the STM in the constant current mode is sensitive to structures buried below surface atoms. We further demonstrate for an experimentally well-characterized system, Ir on Cu(001) [7][8][9], in how far first-principles calculations of the electronic structure can go in analyzing STM-images of complex transition-metal systems.…”

Section: Introductionmentioning

confidence: 89%

“…Gilarowksi et al [7,8] performed experiments combining STM, Ion Scattering Spectroscopy (ISS), X-ray Photoelectron Spectroscopy (XPS) and Low-Energy Electron Diffraction (LEED). STM images were taken at room temperature with a microscope operated in constant-current mode.…”

Section: Summary Of Ir/cu(100) Experimentsmentioning

confidence: 99%

“…Successful imaging of the sub-surface alloy was only possible for negative bias voltages U sample (occupied sample states) in a range between À0:2 and À0:5 V, indicating electronic effects as the origin of the measured corrugation. Summarizing the experimental findings from the STM, LEED, ISS, and XPS measurements, Gilarowski et al [7,8] proposed the following structural model: 0.5 ML of Ir deposited on Cu(001) leads to the formation of an ordered (2Â1) CuIr alloy layer of adjacent Cu and Ir chains along the [011] directions buried under one monolayer of Cu. Although above experimental findings lead to a consistent structural model of an ordered CuIr sub-surface alloy, (i) the result is quite surprising as Ir and Cu exhibit a large miscibility gap in the bulk phase diagram [30], and (ii) the model relies on the assumption that STM is able to image Ir impurities and chains buried in the substrate, for which there is no experimental evidence so far and disputed by the conventional school of thought that STM follow the topography of surface atoms.…”

Section: Summary Of Ir/cu(100) Experimentsmentioning

confidence: 99%

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First-Principles Interpretation of Scanning Tunneling Microscopy Applied to Transition-Metal Surfaces: Buried CuIr/Cu(001) Surface Alloys

Heinze

Bihlmayer

Blügel

2001

phys. stat. sol. (a)

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For the example of scanning tunneling microscopy (STM) experiments, carried out for Ir impurities and chains buried in the sub-surface layer of Cu(001), we represent the present status of analyzing STM experiments of transition-metal surfaces using first-principles calculations based on the density functional theory to describe the electronic structure of the sample, in combination with the model of Tersoff and Hamann to evaluate the tunneling current between tip and sample. We show that transition-metal defect structures below the Cu(001) surface can be detected by STM and the detection should not be restricted to Ir defects nor to the sub-surface layer.

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“…Regarding STM, in some cases second-layer (subsurface) atoms have been observed with an apparent height larger than that of first-layer (surface) atoms, e.g., Ti/Pt(100) [14] and Ir/Cu(100) [15][16][17]. Ge atoms are apparently observed as brighter than Pt atoms in the c(2 × 2) layer [8,9], and additional techniques such as ALISS are needed to determine accurate atomic positions in studies of surface morphology.…”

Section: Introductionmentioning

confidence: 99%

Ge overlayer and surface alloy structures on Pt(100) studied using alkali ion scattering spectroscopy, x-ray photoelectron spectroscopy and x-ray photoelectron diffraction

Matsumoto¹,

Ho²,

Batzill³

et al. 2014

J. Phys.: Condens. Matter

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We have investigated surface structures formed by deposition of Ge on a Pt(100) substrate by using a multi-technique approach utilizing alkali ion scattering spectroscopy (ALISS), x-ray photoelectron spectroscopy (XPS), and x-ray photoelectron diffraction (XPD). ALISS was used to distinguish Ge overlayers from incorporated alloy layers for the surface structures reported, and to supply structural information about the surface alloy or 'layer compound' formed by the deposition of 1.5-ML Ge. A Ge adlayer forms following the deposition of 0.2-ML Ge on Pt(100) and annealing at 600 K. ALISS revealed that Ge adatoms in these overlayers had 1D (incomplete c(2 × 2)) Ge-Ge ordering along [010] and equivalent directions, even though this was not directly apparent in observations using LEED and STM. A c(2 × 2)-Ge overlayer was produced after 0.5 ML-Ge deposition on Pt(100) and annealing at 600 K. Deposition of 1.5-ML Ge on Pt(100) and annealing at 600 K caused extensive Ge interdiffusion into the third (subsurface) layer, while the first and second layers remained as a c(2 × 2) Ge overlayer and (1 × 1) Pt layer, respectively. We propose that the Pt(100) substrate thus is 'capped' by an alloy film with the structure of a body-centered tetragonal Pt2Ge layer compound, which is terminated by a pure-Ge layer that is indistinguishable from a c(2 × 2)-Ge adlayer. This explains the apparently 'strange' result that even though extensive Ge interdiffusion was occurring deeply into the Pt bulk during annealing at 900 and 1200 K, a Ge overlayer remained on the surface. XPS spectra showed a +0.5 eV binding energy shift of the Ge 3d core level and a small (0-0.1 eV) positive shift of the Pt 5d core level compared to Ge(100) and Pt(100) surfaces for the c(2 × 2)-Ge overlayer. There was no effect on these binding energies upon formation of the Pt2Ge layer compound at the surface, and this indicates similar Ge-Pt interactions in the two cases. Compared to other overlayers of Group-IV atoms on metal surfaces, the Ge overlayer on Pt(100) was extraordinarily stable.

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Iridium on Cu(100): Surface Segregation and Alloying

Cited by 12 publications

References 12 publications

Influence of Substrate Materials on Nucleation and Properties of Iridium Thin Films Grown by ALD

Influence of Substrate Materials on Nucleation and Properties of Iridium Thin Films Grown by ALD

First-Principles Interpretation of Scanning Tunneling Microscopy Applied to Transition-Metal Surfaces: Buried CuIr/Cu(001) Surface Alloys

Ge overlayer and surface alloy structures on Pt(100) studied using alkali ion scattering spectroscopy, x-ray photoelectron spectroscopy and x-ray photoelectron diffraction

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