Packing and molecular orientation of alkanethiol monolayers on gold surfaces

Ulman, Abraham; Eilers, James E.; Tillman, Nolan

doi:10.1021/la00089a003

Cited by 264 publications

(246 citation statements)

References 1 publication

(1 reference statement)

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“…22 These calculations provide explicit predictions of the atomic positions, from which scattering cross sections have been calculated. Typically, the calculated in-plane translational correlation lengths are quite short; this result and the mean molecular tilt for a given mean molecular area 21 are both in agreement with experimental results.…”

Section: J Introductionmentioning

confidence: 99%

X-ray grazing incidence diffraction from alkylsiloxane monolayers on silicon wafers

Tidswell

Rabedeau

Pershan

et al. 1991

The Journal of Chemical Physics

136

103

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X-ray reflection (both specular and off-specular) and grazing incidence diffraction (GID) have been used to study the structure of alkylsiloxane monolayers (n-C18H37SiO1.5) formed by self-assembly from solution on silicon wafers. GID studies of complete monolayers reveal a single ring of scattering associated with the monolayer. The Lorentzian line shape of this ring indicates that the film is characterized by liquidlike order, with a typical translational correlation length of about 45 Å. The thermal coefficient of expansion of the monolayer, as determined from the GID peak position, is approximately equal to the value for liquid n-alkanes. Upon either heating or cooling, the monolayer correlation lengths decrease, suggesting that the differential thermal-expansion coefficients of the film and substrate figure prominently in thermal changes of the molecular ordering. GID data for incomplete monolayers also reveal a single ring of scattering associated with the monolayer. While both the translational correlation lengths and integrated peak areas are significantly reduced relative to complete monolayers, the peak positions of the incomplete monolayers are comparable to those of complete monolayers. Given the lower average areal density of incomplete monolayers, this finding implies that incomplete monolayers are inhomogeneous.

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Section: J Introductionmentioning

confidence: 99%

X-ray grazing incidence diffraction from alkylsiloxane monolayers on silicon wafers

Tidswell

Rabedeau

Pershan

et al. 1991

The Journal of Chemical Physics

136

103

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“…Our observation of non-exfoliation phenomenon is presumably due to the additional energy needed to overcome partially or fully interdigitated interactions between the alkyl chains of the intercalates (Fig. 3b) 30,32,33 .…”

Section: Resultsmentioning

confidence: 83%

Tandem intercalation strategy for single-layer nanosheets as an effective alternative to conventional exfoliation processes

et al. 2015

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Simple and effective generation of transition metal chalcogenides (TMCs) in a single-layer form has been a challenging task. Here we present a tandem molecular intercalation (TMI) as a new exfoliation concept for producing single-layer TMCs from multi-layer colloidal TMC nanostructures in solution phase. TMI requires tandem Lewis base intercalates, where short 'initiator' molecules first intercalate into TMCs to open up the interlayer gap, and the long 'primary' molecules then bring the gap to full width so that a random mixture of intercalates overcomes the interlayer force. Spontaneous exfoliation then yields single-layer TMCs. The TMI process is uniquely advantageous because it works in a simple one-step process under safe and mild conditions (that is, room temperature without sonication or H 2 generation). With the appropriate intercalates, we have successfully generated single-layer nanostructures of group IV (TiS 2 , ZrS 2 ), group V (NbS 2 ) and VI (WSe 2 , MoS 2 ) TMCs.

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“…Since the value of p is described classically as being proportional to the dipole moment derivative with respect to the normal coordinate of vibrational oscillation, 21,32 factors significant to a redistribution of electron density, such as molecular orbital intermixing and van der Waals forces, may result in increased oscillator strength, namely, ͉p SAM ͉ Ͼ ͉p liq ͉. The contribution of such factors stands to the reason given the important role of intermolecular forces driving the selfassembly mechanism, 17,33,34 and follows naturally from the discussion of phase related intensity variation outlined above. Note that in general, ⌬p may occur by virtue of a change in net permanent dipole or by induced dipole effects, i.e., a change in vibrational polarizability.…”

Section: Absorption Enhancement Effectmentioning

confidence: 99%

Observation of surface enhanced IR absorption coefficient in alkanethiol based self-assembled monolayers on GaAs(001)

Marshall

Bensebaa

Dubowski

2009

Journal of Applied Physics

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Alkanethiol self-assembled monolayers (SAMs) of various methylene group chain lengths [HS–(CH2)n–CH3] (n=9,11,13,15,17) were fabricated on the GaAs(001) surface followed by characterization using Fourier transform infrared spectroscopy. Modal analysis of the CH2 stretching mode region (2800–3000 cm−1) showed that linear scaling of the n-dependent factors accurately reproduced the spectral data, supporting a chain-length consistent physical model upon which a measurement of the absorption coefficient was based. Evaluated from the linearity of the absorbance data, a peak coefficient of 3.5×104 cm−1 was obtained and a domain for ordered self-assembly was assigned for values n>9. Compared with measurements of the absorption coefficient made in the liquid phase, the SAM phase coefficient was determined to be about six times greater. This enhancement effect is discussed in terms of contributions relating to the locally ordered environment and is largely attributed to the chemical properties of the interface. We believe this to be the first demonstration of IR spectral enhancement of a molecular species chemisorbed on the semiconductor surface.

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Packing and molecular orientation of alkanethiol monolayers on gold surfaces

Cited by 264 publications

References 1 publication

X-ray grazing incidence diffraction from alkylsiloxane monolayers on silicon wafers

X-ray grazing incidence diffraction from alkylsiloxane monolayers on silicon wafers

Tandem intercalation strategy for single-layer nanosheets as an effective alternative to conventional exfoliation processes

Observation of surface enhanced IR absorption coefficient in alkanethiol based self-assembled monolayers on GaAs(001)

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