Competing interactions of noble metals and fullerenes with the Si(111)7×7 surface

O’Shea, James N.; Phillips, Michael A.; Taylor, Michael D.; Beton, Peter H.; Moriarty, Philip; Kanai, Mito; Dennis, T. John S.; Dhanak, Vin; Patel, Shelain; Poolton, N.R.J.

doi:10.1063/1.1628225

Cited by 10 publications

(8 citation statements)

References 32 publications

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“…1,5,35 In the case of Au, XPS, AFM, and IR, results indicate that OTS monolayers are similar to oxide surfaces while directly attached monolayers are similar to H-terminated silicon surfaces highlighting the importance of the substrate in the reactivity under the metal. Previous work has shown that Au reacts with silicon to form a Au 3 Si silicide, 33,34 and the XPS Au core level results are consistent with gold silicide formation. This likely alters the surface chemistry enough to displace the monolayers.…”

Section: Resultssupporting

confidence: 70%

“…The observation of only one Ag oxidation state indicates that Ag does not react with the underlying silicon substrate as expected from previous results showing that silicon and silver do not form a silicide. 34,36 Figure 13 shows the atomic fractions for Ag, Si, C, and O as a function of sputtering time for the alcohol and OTS surfaces. The area of the C 1s peak for the interfacial region (30-75 s) is nearly equivalent for both the alcohol and the OTS in agreement with the observation of organic monolayers under Ag in the IR (Figure 8).…”

Section: Resultsmentioning

confidence: 99%

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Origin of Differing Reactivities of Aliphatic Chains on H−Si(111) and Oxide Surfaces with Metal

et al. 2007

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The interaction of deposited metals with monolayer films is critical to the understanding of, and ultimate utility of, the emerging arena of molecular electronics. We present the results of a thorough study of the interaction of vapor-deposited Au and Ag on alkane films attached to Si substrates. Two distinct categories of films are studied: C18 films formed from the hydrosilation reaction of octadecyl trichlorosilane with thin SiO2 layers and C18 films formed from the direct attachment of functionalized alkanes with hydrogen-terminated Si. Two direct attachment chemistries were studied: (Si)3−Si−O−C linkages of 1-octadecanol and octadecanal on H-terminated Si(111) and (Si)3−Si−C linkages of 1-octadecene on H-terminated Si(111). The reactivity of the films was studied with p-polarized backside reflection absorption spectroscopy (pb-RAIRS), sputter depth profiling X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), and device electrical tests. Independent of direct attachment chemistry, we report the remarkable observation that deposition of Au results in the displacement of the molecular film from the Si interface. In contrast, the directly attached molecular films are robust toward the deposition of Ag. For both metals, the C18 films formed by hydrosilation reactions on SiO2 remain at the interface. The results of monolayer stability with metal are linked to reactions between the metal and substrate. The displacement of the films by Au is attributed to Au insertion in the Si backbonds, in a reaction analogous to silicide formation. The results demonstrate that one must fully take into account the reactivity of the entire system, including substrates, molecular functional groups, and metal electrodes, when considering the robustness of molecules in metal junctions.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Origin of Differing Reactivities of Aliphatic Chains on H−Si(111) and Oxide Surfaces with Metal

et al. 2007

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“…This large shift from the position of metallic Au ( ) indicates a strong interaction between the Au overlay and the Si substrate. This shift is in agreement with earlier studies on annealed Au silicide structures on Si(111) substrates 17 , 52 , 53 and is considerably larger than reported for Au silicide layers obtained at room temperature 16 , 47 , 54 . The branching ratio reduces from about 0.72 for photons to about 0.58 for , while the spin-orbit splitting is taking into account all measurements.…”

Section: Resultssupporting

confidence: 93%

“…Thus, the -component is assigned to the Si bulk. Based on the previous reports on Au silicide structures 16 , 17 , 47 , 52 – 54 , the highest binding energy component can be assigned to Si in Au silicide although the here found chemical shift of this component is slightly lower than the previously reported values. The -component is related to Si at or near the surface, but not bound to Au atoms.…”

Section: Resultssupporting

confidence: 52%

Investigation of single-domain Au silicide nanowires on Si(110) formed for Au coverages in the monolayer regime

Appelfeller

2021

Sci Rep

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The self-organized formation of single domain Au silicide nanowires is observed on Si(110). These nanowires are analysed using scanning tunnelling microscopy (STM) and spectroscopy (STS) as well as photoemission spectroscopy (PES). Core-level PES is utilised to confirm the formation of Au silicide and establish its presence as the top most surface structure, i.e., the nanowires. The growth of the Au silicide nanowires and their dimensions are studied by STM. They form for Au coverages of about 1 monolayer and are characterized by widths of about 2 to 3 nm and heights below 1 nm while reaching lengths exceeding 500 nm when choosing appropriate annealing temperatures. Valence band PES and STS indicate a small but finite density of states at the Fermi level typical for compound metals.

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“…Following a well-established approach [31] , [32] , a C 60 monolayer (ML) was formed on the Si(111)-(7×7) surface to act as a template for the formation of Ag nanoparticles. (This strategy cannot be used to form Au nanoparticles [33] , such as those studied by Stellacci et al As feedback ringing and imaging artefacts are entirely independent of the composition of the nanoparticle, however, our results are equally applicable to Au nanoparticles.) C 60 was first sublimed onto a clean Si(111)-(7×7) surface, formed using standard flash annealing procedures [34] .…”

Section: Methodsmentioning

confidence: 56%

Critical Assessment of the Evidence for Striped Nanoparticles

et al. 2014

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There is now a significant body of literature which reports that stripes form in the ligand shell of suitably functionalised Au nanoparticles. This stripe morphology has been proposed to strongly affect the physicochemical and biochemical properties of the particles. We critique the published evidence for striped nanoparticles in detail, with a particular focus on the interpretation of scanning tunnelling microscopy (STM) data (as this is the only technique which ostensibly provides direct evidence for the presence of stripes). Through a combination of an exhaustive re-analysis of the original data, in addition to new experimental measurements of a simple control sample comprising entirely unfunctionalised particles, we show that all of the STM evidence for striped nanoparticles published to date can instead be explained by a combination of well-known instrumental artefacts, or by issues with data acquisition/analysis protocols. We also critically re-examine the evidence for the presence of ligand stripes which has been claimed to have been found from transmission electron microscopy, nuclear magnetic resonance spectroscopy, small angle neutron scattering experiments, and computer simulations. Although these data can indeed be interpreted in terms of stripe formation, we show that the reported results can alternatively be explained as arising from a combination of instrumental artefacts and inadequate data analysis techniques.

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Competing interactions of noble metals and fullerenes with the Si(111)7×7 surface

Cited by 10 publications

References 32 publications

Origin of Differing Reactivities of Aliphatic Chains on H−Si(111) and Oxide Surfaces with Metal

Origin of Differing Reactivities of Aliphatic Chains on H−Si(111) and Oxide Surfaces with Metal

Investigation of single-domain Au silicide nanowires on Si(110) formed for Au coverages in the monolayer regime

Critical Assessment of the Evidence for Striped Nanoparticles

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