Infrared spectroscopic analysis of an ordered Si/SiO2 interface

Queeney, K. T.; Herbots, Nicole; Shaw, Justin M.; Atluri, V.; Chabal, Yves J.

doi:10.1063/1.1644030

Cited by 62 publications

(43 citation statements)

References 9 publications

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“…There is observable oxidation of the silicon surface as evidenced by positive absorption modes at ∼1050 cm -1 and ∼1220 cm -1 , which correspond to the asymmetric Si-O-Si transverse optical (TO) and Si-O-Si longitudinal optical (LO) stretching modes, respectively. 71 The frequency of the LO mode indicates that the regions of oxide (SiO 2 ) are very small in physical size, 72,73 possibly including as few as 10 oxygen atoms. 74 This is consistent with scanning tunneling microscopy observations that oxidation of H-Si(111) surfaces occurs in randomly distributed 10-20 Å diameter domains.…”

Section: Resultsmentioning

confidence: 99%

Investigation of the Chemical Purity of Silicon Surfaces Reacted with Liquid Methanol

et al. 2008

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The reaction of hydrogen-terminated Si(111) and oxide-terminated silicon surfaces with neat anhydrous liquid methanol (CH 3 OH) has been studied with Fourier transform infrared spectroscopy (FTIR) as a function of solution temperature and immersion time. At 65°C, reaction of atomically smooth H-Si(111) surfaces with CH 3 OH (l) results in partially methoxylated silicon surfaces that are free of any detectable subsurface oxidation (Si-O-Si bonds); this is in contrast to observable oxidation found after similar reactions on H-Si(100) surfaces. At long reaction times (t > 3 h), the Si(111) surface saturates with Si-OCH 3 sites at a coverage of approximately 30% of a monolayer, with the residual ∼70% comprised of unreacted Si-H sites. The lack of any detectable silicon oxide makes it possible to conclude the following: (i) Reaction mechanisms involving insertion of oxygen atoms from the CH 3 OH molecule into the subsurface Si-Si back bonds cannot be dominant for (111)-oriented silicon under these conditions. (ii) The vibrational modes of the oxide-free surface are very sharp and can be clearly distinguished from blue-shifted modes observed for methoxyl groups chemisorbed on oxidized surfaces. For surfaces that display subsurface oxidation, no evidence for oxygen atoms directly below atop Si-H sites has been observed. Instead, FTIR analysis demonstrates that subsurface oxidation selectively exists underneath atop Si-OCH 3 sites. Finally, H-terminated oxide surfaces, prepared by reacting trichlorosilanes on OH-terminated SiO 2 surfaces, react with methanol to form a methoxy-terminated oxide surface.

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Section: Resultsmentioning

confidence: 99%

Investigation of the Chemical Purity of Silicon Surfaces Reacted with Liquid Methanol

et al. 2008

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“…The asymmetrical Si-O-Si stretch undergoes a phonon splitting between longitudinal optic (LO) and transverse optic (TO) components. It has been shown 122,123 that in a thin SiO 2 film, the TO vibrations are parallel to the film surface while the LO vibrations are perpendicular to it. Both components can be observed in GA-ATR; the band at 1230 cm -1 has been assigned to the LO mode, and the band at 1045 cm -1 to the corresponding TO mode.…”

Section: Vibrational Spectroscopies: Ir and Ramanmentioning

confidence: 99%

Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

et al. 2013

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“…The films were produced by SiO evaporation and subsequent condensation on a Si(111) substrate hold at 300 K. Two broad features develop with growing film thickness. The stronger one at 983 cm −1 is assigned to the asymmetric stretching mode of the oxygen atom in a Si-O-Si bridge against the Si-neighbour atoms (Philipp 1971;Chabal et al 2002;Queeney et al 2004;Cachard et al 1971;Lehmann et al 1983Lehmann et al , 1984. The much weaker structure at approximately 715 cm −1 corresponds to the Si stretching mode, a mode with dominating Si displacement (Lehmann et al 1983), sometimes called "bending" mode in the literature.…”

Section: Resultsmentioning

confidence: 99%

Laboratory measurement of optical constants of solid SiO and application to circumstellar dust

Wetzel

Klevenz

Gail

et al. 2013

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Context. Silicate minerals belong to the most abundant solids that form in cosmic environments. Their formation requires that a sufficient number of oxygen atoms per silicon atom are freely available. For the standard cosmic element mixture this can usually be taken for granted, but it becomes a problem at the transition from the oxygen-rich chemistry of M-stars to the carbon-rich chemistry of C-stars. In the intermediate type S-stars, most of the oxygen and carbon is consumed by formation of CO and SiO molecules, and left-over oxygen to build SiO 4 -tetrahedrons in solids becomes scarce. Under such conditions SiO molecules from the gas phase may condense into solid SiO. The infrared absorption spectrum of solid SiO differs from that of normal silicates by the absence of Si-O-Si bending modes around 18 μm whereas the absorption band due to Si-O bond stretching modes at about 10 μm is present. Observations show that exactly this particular characteristic can be found in some S-star spectra. Aims. We demonstrate that this observation may be explained by the formation of solid SiO as a major dust component at C/O abundance ratios close to unity. Methods. The infrared absorption properties of solid SiO are determined by laboratory transmission measurements of thin films of SiO produced by vapour deposition on a Si(111) wafer in the range between 100 cm −1 and 5000 cm −1 (2 μm and 100 μm). From the measured spectra the dielectric function of SiO is derived by using a Brendel-oscillator model, particularly suited to the representation of optical properties of amorphous materials. The results are used in model calculations of radiative transfer in circumstellar dust shells with solid SiO dust in order to determine the spectral features due to SiO dust. Results. Comparison of synthetic and observed spectra shows that reasonable agreement is obtained between the main spectral characteristics of emission bands due to solid silicon monoxide and an emission band centred on 10 μm, but without the accompanying 18μm band, observed in some S-stars. We propose that solid SiO is the carrier material of this 10 μm spectral feature.

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Infrared spectroscopic analysis of an ordered Si/SiO2 interface

Cited by 62 publications

References 9 publications

Investigation of the Chemical Purity of Silicon Surfaces Reacted with Liquid Methanol

Investigation of the Chemical Purity of Silicon Surfaces Reacted with Liquid Methanol

Silica Surface Features and Their Role in the Adsorption of Biomolecules: Computational Modeling and Experiments

Laboratory measurement of optical constants of solid SiO and application to circumstellar dust

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