Optical Constant Determination in the Infrared of Uniaxially Oriented Monolayers from Transmittance and Reflectance Measurements

Buffeteau, Thierry; Blaudez, D.; Péré, and E.; Desbat, Bernard

doi:10.1021/jp9847991

Cited by 73 publications

(119 citation statements)

References 38 publications

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“…A series of the MO measurements has been performed on the basis of approximation 10. 11,13,18,24,30,31,32,[49][50][51] However, the difference between 3k iso and k max can be essential. For example, the value of 3k iso ) 0.79 characterizes bulk CdAr dispersed in KBr pellets, 49 which is distinct from the value of k max ) 1.04 found for a 11-monolayer LB film of CdAr on glass.…”

Section: Methodsmentioning

confidence: 99%

A New Approach to the IR Spectroscopic Study of Molecular Orientation and Packing in Adsorbed Monolayers. Orientation and Packing of Long-Chain Primary Amines and Alcohols on Quartz

and

Rao

2001

J. Phys. Chem. B

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A new method is suggested for determining the molecular orientation in adsorbed films with uniaxial and biaxial anisotropy from two (s-and p-polarized) IRRAS spectra of the same sample, measured at the optimal angle of incidence. The method is simple, does not use the film thickness, and is internally stable with respect to the uncertainty in the input optical parameters of the anisotropic film. The advantages and limitations of the method are discussed. To validate the method, we determined the orientation of hexadecylamine and hexadecyl alcohol adsorbed on a quartz surface. It is shown that at a concentration above the concentration of 2D precipitation but below the concentration of 3D precipitation, hydrocarbon chains in the adsorbed amine monolayer are well-packed in a monoclinic (biaxial) subcell with a tilt angle of about 30°. Chaotically arranged crystallites of the amine molecules appear at the surface at a concentration higher than the concentration of 3D precipitation. Adsorbed monolayers of the alcohol turn out to have a hexagonal structure, in which the hydrocarbon tails are "flip-flop" positioned and tilted by 25-30°from the surface normal.

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Section: Methodsmentioning

confidence: 99%

A New Approach to the IR Spectroscopic Study of Molecular Orientation and Packing in Adsorbed Monolayers. Orientation and Packing of Long-Chain Primary Amines and Alcohols on Quartz

and

Rao

2001

J. Phys. Chem. B

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“…These spectral modifications can be explained from simulation of PM-IRRAS spectra using a program developed in the L.P.C.M laboratory. 27 Indeed, a slight modification of the isotropic extinction coefficient of the v as (Si-O-Si) mode ͑with k Ќ уk ʈ ) on a thickness of about 0.5 m allows us to reproduce the signal modification observed for poled surfaces in the 1000-1100 cm Ϫ1 spectral range ͑Fig. 11͒.…”

Section: B Ftir Spectroscopymentioning

confidence: 92%

X-ray absorption and infrared reflectance of poled silica glass for second harmonic generation

Nazabal

Fargin

Flem

et al. 2000

Journal of Applied Physics

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Structural alterations induced by a thermal poling treatment which is at the origin of second harmonic generation in a Herasil silica glass are studied by x-ray absorption near-edge spectroscopy (XANES). Multiple scattering calculations are performed to explain the experimental O–K edge XANES shape of unpoled surfaces of the glass and then to interpret modifications resulting from poling. The observations are consistent with emergence of disorder by breaking Si–O bridging bonds which are not completely removed by a thermal depoling treatment. Fourier transform infrared spectroscopy shows modifications of nonbridging oxygen bonds which are coherent with a model involving a protons migration during poling. Moreover, a partial anisotropy in the direction of the electrostatic field which is applied during the poling treatment is observed.

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“…Yamamoto and Ishida [115,142] extended Hansen's method to the case of biaxial anisotropy. Based on the matrix method of Ohta and Ishida [134] and the generalization of Yamamoto and Ishida [115,142], Buffeteau et al [143] suggested the computation procedure applicable for an arbitrary succession of coherent anisotropic and incoherent layers.…”

Section: Input Mediummentioning

confidence: 99%

Absorption and Reflection of Infrared Radiation by Ultrathin Films

Tolstoy¹,

Чернышова²,

Skryshevsky³

2003

Handbook of Infrared Spectroscopy of Ultrathin Films

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The primary characteristics that one identifies from infrared (IR) spectra of ultrathin films for further analysis are the resonance frequencies, oscillator strengths (extinction coefficients), and damping (bandwidths), related to different kinds of vibrational, translational, and frustrated rotational motion inside the thin-film material [1][2][3][4][5][6][7]. However, the microscopic processes inside or at the surface of a film (motion of atoms and electrons) give rise to the frequency dependence (the dispersion) not only of the extinction coefficient but also of the refractive index of the film. As a result, a real IR spectrum of an ultrathin film is, as a rule, distorted by so-called optical effects. Specifically, the spectrum strongly depends upon the conditions of the measurement, the film thickness, and the optical parameters of the surroundings and substrate impeding extraction of physically meaningful information from the spectrum. Thus after introduction of the nomenclature accepted in optical spectroscopy and a brief discussion of the physical mechanisms responsible for absorption by solids on a qualitative level, this introductory chapter will concentrate on the basic macroscopic or phenomenological theory of the optical response of an ultrathin film immobilized on a surface or at an interface.The theoretical analysis of the IR spectra of ultrathin films on various substrates and at interfaces will involve two assumptions: (1) the problem is linear and (2) the system under investigation is macroscopic; that is, one can use the macroscopic Maxwell formulas containing the local permittivity. The first assumption is valid only for weak fields. The second assumption means that the volume considered for averaging, a (the volume in which the local permittivity is formed), is lower than the parameter of inhomogeneity of the medium, d (e.g., the effective thickness of the film, the size of islands, or an effective dimension of polariton), a < d. In this case, the response of the medium to the external electromagnetic field is essentially the response of a continuum. The 1

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Optical Constant Determination in the Infrared of Uniaxially Oriented Monolayers from Transmittance and Reflectance Measurements

Cited by 73 publications

References 38 publications

A New Approach to the IR Spectroscopic Study of Molecular Orientation and Packing in Adsorbed Monolayers. Orientation and Packing of Long-Chain Primary Amines and Alcohols on Quartz

A New Approach to the IR Spectroscopic Study of Molecular Orientation and Packing in Adsorbed Monolayers. Orientation and Packing of Long-Chain Primary Amines and Alcohols on Quartz

X-ray absorption and infrared reflectance of poled silica glass for second harmonic generation

Absorption and Reflection of Infrared Radiation by Ultrathin Films

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