Probing Surface-Adlayer Conjugation on Organic-Modified Si(111) Surfaces with Microscopy, Scattering, Spectroscopy, and Density Functional Theory

Kellar, Joshua A.; Lin, Jui Ching; Kim, Jun‐Hyun; Yoder, Nathan L.; Bevan, Kirk H.; Stokes, Grace Y.; Geiger, Franz M.; Nguyen, SonBinh T.; Bedzyk, Michael J.; Hersam, Mark C.

doi:10.1021/jp8100249

Cited by 10 publications

(30 citation statements)

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“…Aromatic C−H stretch peaks were observed at 3030 and 3070 cm −1 , in agreement with past findings for similar monolayers. 38,53,54 An aliphatic C−H antisymmetric stretch peak was observed at 2929 ± 1 cm −1 . This value is 10 cm −1 higher (blue-shifted) than that of a wellpacked 16-carbon long alkyl monolayers on a reduced silicon surface, 55 indicating weak interactions between neighboring chains, which is reasonable for alkyl chains consisting of no more than three methylene units.…”

Section: Resultsmentioning

confidence: 99%

“…The has a slightly more up-right orientation (14°). 38 This difference reflects the odd−even tether effect on ring orientation 45 (the tether length is 2, 1, and 3 for styrene, 38 phenol, 61 and PhX, respectively). The similar ring orientation for the three PhX monolayers is in qualitative agreement with results of water contact angle measurements (elaborated below) and DFT calculations (see Table 2).…”

Section: Resultsmentioning

confidence: 99%

“…Overall, surface characterization indicates that despite their short length (∼1 nm) all three monomers yield fairly ordered monolayers, in agreement with previous studies of monolayers with aromatic moieties on Si. 18,38,72 This can be rationalized by the proximity of the phenyl rings to each other (<4 Å), imposed by the Si(111) lattice. 45 Such dense binding also explains the lack of Si oxidation ("chemical passivation") as observed by XPS.…”

Section: Resultsmentioning

confidence: 99%

“…48,49 Surfaces were modeled by a periodic slab containing 4 Si surface atoms, of which two are hydrogen bonded and two are bonded to PhX molecules, reflecting a 50% coverage. 18,37,38 All calculations were carried out using the plane wave-based Vienna Ab Initio Simulation Package (VASP). 50…”

Section: Methodsmentioning

confidence: 99%

“…14,35 Molecules can then be bound to H-terminated Si via hydrosilylation of CC bonds, a common route for monolayer formation on reduced Si. 35,36 Steric considerations commonly limit the binding density to 50% (as in alkyl monolayers), 18,37 though higher (approaching 2/3) 33,38 and lower (1/3) 39 binding densities are also possible.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

et al. 2018

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Molecular monolayers at metal/semiconductor heterointerfaces affect electronic energy level alignment at the interface by modifying the interface's electrical dipole. On a free surface, the molecular dipole is usually manipulated by means of substitution at its external end. However, at an interface such outer substituents are in close proximity to the top contact, making the distinction between molecular and interfacial effects difficult. To examine how the interface dipole would be influenced by a single atom, internal to the molecule, we used a series of three molecules of identical binding and tail groups, differing only in the inner atom: aryl vinyl ether (PhO), aryl vinyl sulfide (PhS), and the corresponding molecule with a CH 2 groupallyl benzene (PhC). Molecular monolayers based on all three molecules have been adsorbed on a flat, oxide-free Si surface. Extensive surface characterization, supported by density functional theory calculations, revealed high-quality, well-aligned monolayers exhibiting excellent chemical and electrical passivation of the silicon substrate, in all three cases. Current−voltage and capacitance−voltage analysis of Hg/PhX (X = C, O, S)/Si interfaces established that the type of internal atom has a significant effect on the Schottky barrier height at the interface, i.e., on the energy level alignment. Surprisingly, despite the formal chemical separation of the internal atom and the metallic electrode, Schottky barrier heights were not correlated to changes in the semiconductor's effective work function, deduced from Kelvin probe and ultraviolet photoemission spectroscopy on the monolayer-adsorbed Si surface. Rather, these changes correlated well with the ionization potential of the surface-adsorbed molecules. This is interpreted in terms of additional polarization at the molecule/metal interface, driven by potential equilibration considerations even in the absence of a formal chemical bond to the top Hg contact.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

et al. 2018

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1‐Bromo‐4‐ethynylbenzene on Cu(100): Adsorption, bonding structures, and reaction mechanisms

Chiang

Liu

You

et al. 2022

J Chinese Chemical Soc

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Temperature‐programmed reaction/desorption, X‐ray photoelectron spectroscopy, reflection‐absorption infrared spectroscopy, near edge X‐ray absorption fine structure and density functional theory calculations have been employed to investigate the adsorption, bonding structures, and reaction pathways of 1‐bromo‐4‐ethynylbenzene (BrC6H4C ≡ CH, 1Br4EB) on Cu(100). This molecule is chemically adsorbed, via the ethynyl group attaching to the surface, forming two C‐Cu bonds and a ~ 60° tilting aromatic plane with respect to the surface. At 370 K, dissociation of both the C‐Br and CC‐H bonds of 1‐bromo‐4‐ethynylbenzene generates adsorbed intermediates of C6H5C2, C6H4C2H2, and C6H4C2. The C‐Br breakage temperature is much higher than those (~ 240 K) observed in the cases of bromobenzene/Pt(111) and dibromopyridine/Cu(100), owing to the adsorption geometry of 1‐bromo‐4‐ethylnylbenzene, with the C‐Br pointing away from the surface. In the case of higher coverages, molecular desorption occurs near 370 K. The adsorption structures of the aromatic intermediates of C6H4CHCH, C6H4CCH2, C6H4CH2C, C6H4C2, and C6H5C2 are calculated and compared. They are stable up to ~520 K and decompose to form H2 at higher temperatures (~520–870 K). No hydrocarbon products, such as C2H2, C2H4, C6H6, C6H5CCH, or C6H5CHCH2, are measured.

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Phenylacetylene One-Dimensional Nanostructures on the Si(100)-2 × 1:H Surface

et al. 2010

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Using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM), many olefins have been shown to self-assemble on the hydrogen-passivated Si(100)-2 x 1 surface into one-dimensional nanostructures. This paper demonstrates that similar one-dimensional nanostructures can also be realized using alkynes. In particular, UHV STM, sum frequency generation (SFG), and density functional theory (DFT) are employed to study the growth mechanism and binding configuration of phenylacetylene (PA) one-dimensional nanostructures on the Si(100)-2 x 1:H surface. Molecular-resolution UHV STM images reveal the binding position and spacing of PA with respect to the underlying silicon dimer rows. Furthermore, UHV STM characterization of heteromolecular one-dimensional nanostructures of styrene and PA shows distinct electronic contrast between the two molecules, which is confirmed using simulated STM images derived from DFT and provides insight into the nature of PA binding to silicon. Additional evidence from SFG measurements corroborates the conclusion that the terminal carbon atoms of PA retain pi-conjugation following reaction to the Si(100)-2 x 1:H surface.

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Probing Surface-Adlayer Conjugation on Organic-Modified Si(111) Surfaces with Microscopy, Scattering, Spectroscopy, and Density Functional Theory

Cited by 10 publications

References 72 publications

Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

Effect of Internal Heteroatoms on Level Alignment at Metal/Molecular Monolayer/Si Interfaces

1‐Bromo‐4‐ethynylbenzene on Cu(100): Adsorption, bonding structures, and reaction mechanisms

Phenylacetylene One-Dimensional Nanostructures on the Si(100)-2 × 1:H Surface

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