Molecular orientation of adsorbates on metal and semiconductor surfaces determined by external reflection infrared spectroscopy

Hoffmann, Helmuth; Mayer, U.; Brunner, H.; Krischanitz, Anton

doi:10.1016/0022-2860(95)08770-v

Cited by 10 publications

(19 citation statements)

References 4 publications

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“…4) peaks as expected for such an external reflection infrared experiment on a silicon substrate. As clearly stated by Hoffman et al 41,42 a highly ordered alkyl monolayer should exhibit strongly positive peaks at ~2920 and ~2850 cm -1 (methylene asymmetric ν a (CH 2 ) and symmetric modes ν s (CH 2 )) and negative peaks (of much lower amplitude) at ~2968 and ~2879 cm -1 arising from methyl vibration modes (ν a (CH 3 ) ip and ν s (CH 3 ), respectively). A strongly disordered, liquid-like, film shows only negative peaks.…”

Section: -Octadecene Monolayers On N + -Type Surfacesmentioning

confidence: 76%

“…4) peaks, as expected for such an external reflection infrared experiment on a silicon substrate. As clearly stated by Hoffman et al, 41,42 a highly TABLE I. Water and hexadecane contact angles, Zisman critical surface tension, and monolayer thickness (ellipsometry) for the different samples made on silicon with a large range of doping.…”

Section: -Octadecene Monolayers On N + -Type Surfacesmentioning

confidence: 87%

“…40 Measurements were performed in the external reflection mode (for highly doped n + -type substrate) as described elsewhere. 41,42 After monolayer formation, we systematically measured the peak position of the symmetric and antisymmetric stretching modes of the CH 2 group. This is a useful tool to ascribe the degree of molecular order in the monolayers.…”

Section: Infrared Spectroscopymentioning

confidence: 99%

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1-octadecene monolayers on Si(111) hydrogen-terminated surfaces: Effect of substrate doping

Miramond

Vuillaume

2004

Journal of Applied Physics

100

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Enhanced photoanode properties of epitaxial Ti doped α-Fe2O3 (0001) thin films Appl. Phys. Lett. 101, 133908 (2012) Structure and optical band gap of ZnO1−xSx thin films synthesized by chemical spray pyrolysis for application in solar cells J. Appl. Phys. 112, 063708 (2012) Roto-flexoelectric coupling impact on the phase diagrams and pyroelectricity of thin SrTiO3 films J. Appl. Phys. 112, 064111 (2012) Plasmonic effects of ultra-thin Mo films on hydrogenated amorphous Si photovoltaic cellsWe have studied the electronic properties, in relation to structural properties, of monolayers of 1-octadecene attached on a hydrogen-terminated (111) silicon surface. The molecules are attached using the free-radical reaction between C v C and Siu H activated by an ultraviolet illumination. We have compared the structural and electrical properties of monolayers formed on silicon substrates of different types (n type and p type) and different doping concentrations, from low-doped ͑ϳ10 14 cm −3 ͒ to highly doped ͑ϳ10 19 cm −3 ͒. We show that the monolayers on n-, p-, and p + -silicon are densely packed and that they act as very good insulating films at a nanometer thickness with leakage currents as low as ϳ10 −7 A cm −2 and high-quality capacitance-voltage characteristics. The monolayers formed on n + -type silicon are more disordered and therefore exhibit larger leakage current densities ͑Ͼ10 −4 A cm −2 ͒ when embedded in a silicon/monolayer/metal junction. The inferior structural and electronic properties obtained with n + -type silicon pinpoint the important role of surface potential and of the position of the surface Fermi level during the chemisorption of the organic monolayers.

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Section: -Octadecene Monolayers On N + -Type Surfacesmentioning

confidence: 76%

Section: -Octadecene Monolayers On N + -Type Surfacesmentioning

confidence: 87%

Section: Infrared Spectroscopymentioning

confidence: 99%

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1-octadecene monolayers on Si(111) hydrogen-terminated surfaces: Effect of substrate doping

Miramond

Vuillaume

2004

Journal of Applied Physics

100

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“…SAMs of organosulfur compounds on metal surfaces such as Au and Ag have been extensively studied. ,,,− This class of SAM, one based on a fairly simple chemical adsorption process, has been studied by numerous physical and spectroscopic techniques, and their structure is now well understood. The structures of monolayers of organosilanes (such as octadecyltrichlorosilane (OTS)) adsorbed on oxide surfaces like glass, Al 2 O 3 , SiO 2 , and ITO also have been investigated by numerous groups, ,,− but due to their extreme sensitivity to the methods of preparation used, their character remains less well understood. In general, it is found that the OTS chains can pack with densities approaching those found in bulk hydrocarbon crystals but that even the “highest quality” phases lack the long-range translational ordering found for thiolate SAMs on Au and Ag.…”

Section: Introductionmentioning

confidence: 99%

“…Hoffmann et al − have reported structural information about alkylsiloxane monolayers formed on silicon surfaces. Using reflection absorption infrared spectroscopy (RAIRS), they observed highly oriented, crystalline-like structures for long-chain molecules, including OTS, in which the hydrocarbon chains are tilted by an average of ∼8° from the surface normal direction.…”

Section: Introductionmentioning

confidence: 99%

Structure and Stability of Patterned Self-Assembled Films of Octadecyltrichlorosilane Formed by Contact Printing

et al. 1997

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The structures of thin films of octadecyltrichlorosilane (OTS) formed by contact printing and adsorption from solution on Al and SiO2/Si surfaces have been investigated by X-ray photoelectron spectroscopy (XPS), ellipsometry, reflection-absorption infrared spectroscopy (RAIRS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The structures of the OTS films were found to be strongly influenced by the method of preparation used. The films formed by contact printing for 30 s with an OTS "ink" are composed of close-packed, predominantly all-trans alkyl chains aligned nearly perpendicular to the surface, while films formed by adsorption of OTS for 30 s from a solution of comparable concentration are made up of sparsely adsorbed and more randomly oriented chains. Large changes in the film structure (from conformationally disordered, poorly oriented to well-packed, highly oriented hydrocarbon chains) were observed as the reaction time was increased for samples prepared by immersion in an OTS-containing solution (e.g. 15-30 min in a 1 mM solution). On the other hand, films prepared by contact printing reached or exceeded full monolayer mass coverages after only 30 s of substrate contact with an elastomeric stamp inked with a 10 mM solution of OTS in hexane. The OTS films formed by contact printing are stable at the high temperatures and aggressive reaction conditions necessary for their use as molecular resists in directing the selective deposition of metal and ceramic thin films by MOCVD and sol-gel methods, respectively. In this paper we show how such factors as the OTS ink concentration and stamp contact time influence the patterning of OTS thin films by microcontact printing. We find that reactive spreading and island formation of OTS domains in regions of the pattern not in contact with the stamp limit the fidelity of the patterning carried out at dimensions less than a few microns. We discuss several aspects of the physical processing which mediate these effects and propose possible methods for eliminating or greatly reducing them.

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Monolayer Formation of Organosilane Compounds on Hydroxylic Surfaces

Brunner

Gibson

Mayer

et al. 1997

Progress in Fourier Transform Spectroscopy

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Molecular orientation of adsorbates on metal and semiconductor surfaces determined by external reflection infrared spectroscopy

Cited by 10 publications

References 4 publications

1-octadecene monolayers on Si(111) hydrogen-terminated surfaces: Effect of substrate doping

1-octadecene monolayers on Si(111) hydrogen-terminated surfaces: Effect of substrate doping

Structure and Stability of Patterned Self-Assembled Films of Octadecyltrichlorosilane Formed by Contact Printing

Monolayer Formation of Organosilane Compounds on Hydroxylic Surfaces

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