Electronic structure of hydrogen-terminated silicon surfaces [H-Si(111)] studied by two-photon photoemission

Nakamura, Tsuneyuki; Miyajima, Ken; Hirata, Naoyuki; Matsumoto, Takeshi; Morikawa, Yoshitada; Tada, Hayato; Nakajima, Atsushi

doi:10.1007/s00339-009-5539-x

Cited by 9 publications

(13 citation statements)

References 38 publications

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“…As E 1/2 measured in the dark falls near 0 V vs SCE, E (Si +/0 ) is estimated using eq to lie within the Si band gap, at approximately −4.7 eV. The electrons comprising this electronic state are likely associated with a surface resonance that has been identified on the H–Si(111) surface . This surface resonance has been estimated to lie ∼0.1 eV below E vb in vacuum, − but hydrogen bonding between CH 3 OH and the H–Si(111) surface is predicted to increase the electron density at the Si surface, shifting the electrons in the surface resonance more positive in energy.…”

Section: Discussionmentioning

confidence: 99%

“…The electrons that comprise this electronic state are likely associated with a surface resonance that has been identified on the H-Si(111) surface. 74 This surface resonance has been estimated to lie ~0.1 eV below E vb in vacuum, [74][75][76] but hydrogen bonding between CH 3 OH and the H-Si (111) surface is predicted to increase the electron density at the Si surface, shifting the electrons in the surface resonance more positive in energy. Oxidation of the surface resonance completes the first half of the proposed pathway, leading to methoxylation of the H-Si(111) surface.…”

Section: Iiic Potentiostatic Reaction Of H-si(111) With Ch 3 Oh Thmentioning

confidence: 99%

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A Mechanistic Study of the Oxidative Reaction of Hydrogen-Terminated Si(111) Surfaces with Liquid Methanol

et al. 2017

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H-Si(111) surfaces have been reacted with liquid methanol (CH 3 OH) in the absence or presence of a series of oxidants and/or illumination. Oxidant-activated methoxylation of HSi(111) surfaces was observed in the dark after exposure to CH 3 OH solutions that contained the one-electron oxidants acetylferrocenium, ferrocenium, or 1,1'-dimethylferrocenium. The oxidant-activated reactivity toward CH 3 OH of intrinsic and n-type H-Si(111) surfaces increased upon exposure to ambient light. The results suggest that oxidant-activated methoxylation requires that two conditions be met: (1) the position of the quasi-Fermi levels must energetically favor oxidation of the H-Si(111) surface and (2) the position of the quasi-Fermi levels must energetically favor reduction of an oxidant in solution. Consistently, illuminated n-type HSi(111) surfaces underwent methoxylation under applied external bias more rapidly and at more negative potentials than p-type H-Si(111) surfaces. The results under potentiostatic control indicate that only conditions that favor oxidation of the H-Si(111) surface need be met, with charge balance at the surface maintained by current flow at the back of the electrode. The results are described by a mechanistic framework that analyzes the positions of the quasi-Fermi levels relative to the energy levels relevant for each system.

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Section: Discussionmentioning

confidence: 99%

Section: Iiic Potentiostatic Reaction Of H-si(111) With Ch 3 Oh Thmentioning

confidence: 99%

A Mechanistic Study of the Oxidative Reaction of Hydrogen-Terminated Si(111) Surfaces with Liquid Methanol

et al. 2017

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“…Energy level diagram showing the valence and conduction bands of Si(111)-H and porous Si, along with LUMO energies of the additives (additive LUMO levels from reduction potentials, Si(111)-H from ref , and PS from ref ).…”

Section: Discussionmentioning

confidence: 99%

UV-Initiated Hydrosilylation on Hydrogen-Terminated Silicon (111): Rate Coefficient Increase of Two Orders of Magnitude in the Presence of Aromatic Electron Acceptors

Huck

Buriak

2012

Langmuir

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UV-initiated (254 nm) hydrosilylation of hexadecene on Si(111)-H has been studied in the presence of various aliphatic and aromatic molecules (additives). Many of these additives cause an enhancement in the pseudo-first-order rate coefficient (k(obs)) of hydrosilylation, some up to 200× faster than observed in neat hexadecene. It is proposed that these additives capture the photoejected electron from the surface, thereby increasing the probability of reaction of the alkene with the surface hole (h(+)), leading to Si-C bond formation. While the ability of these additives to increase k(obs) is related to their reduction potential, aromatic additives are particularly efficient; we suspect this is due to the relatively strong physisorption of the aromatic molecules leading to a favorable geometry for electron transfer. The presence of these additives permits the use of a much lower intensity of UV light (~30 μW/cm(2)), reducing the probability of photodegradation of the monolayer, and maximum coverage can be reached within minutes.

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“…The experimental details of the preparation of C n -SAM/Au(111) substrate and 2PPE measurements have been described previously. − Briefly, an Au(111) single crystal ( d = 10 mm, t = 1 mm, orientation accuracy of <0.1°, MaTecK corporation) was used as a substrate. The Au(111) surface was cleaned by repeated cycles of Ar + ion sputtering (0.6 kV, ∼1 μA, 15 min) and annealing (770 K, 30 min) in an ultrahigh vacuum (UHV) chamber.…”

Section: Methodsmentioning

confidence: 99%

Electronic States of Alkanethiolate Self-Assembled Monolayers on Au(111) Studied by Two-Photon Photoemission Spectroscopy

et al. 2012

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Two-photon photoemission (2PPE) spectroscopy has been employed to probe the electronic states of n-alkanethiolate self-assembled monolayers (SAMs) on an Au(111) substrate fabricated in a wet chemical process. Electronic states newly formed in the SAM formation were observed below and above the Fermi level (E F) for various alkyl chain lengths of C12-, C18-, and C22-SAMs. At 3.5–3.7 eV above E F, an unoccupied state originating from a bond between gold and sulfur atoms appears, a state that shows little dispersion with parallel to the surface. The peak position of the unoccupied state depends on the substrate temperature, and it was stabilized with increasing temperature; E F +3.7 eV at 85 K and E F +3.5 eV at 330 K for C18-SAM. The stabilization of the state is attributed to the increase of intermolecular interaction at sulfur atoms with their neighboring S atoms, which is caused by a change in the tilt angle of the alkyl chains in the SAM: on increasing the temperature, the interaction between S atoms in the SAM is promoted by the more upright alkyl chains.

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Electronic structure of hydrogen-terminated silicon surfaces [H-Si(111)] studied by two-photon photoemission

Cited by 9 publications

References 38 publications

A Mechanistic Study of the Oxidative Reaction of Hydrogen-Terminated Si(111) Surfaces with Liquid Methanol

A Mechanistic Study of the Oxidative Reaction of Hydrogen-Terminated Si(111) Surfaces with Liquid Methanol

UV-Initiated Hydrosilylation on Hydrogen-Terminated Silicon (111): Rate Coefficient Increase of Two Orders of Magnitude in the Presence of Aromatic Electron Acceptors

Electronic States of Alkanethiolate Self-Assembled Monolayers on Au(111) Studied by Two-Photon Photoemission Spectroscopy

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