Polarizable dipole models for reflectance anisotropy spectroscopy: a review

Arzate, N.; Mendoza, Bernardo S.; Vázquez-Nava, R. A.

doi:10.1088/0953-8984/16/39/002

Cited by 14 publications

(10 citation statements)

References 89 publications

(130 reference statements)

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“…In a recent theoretical work [12,13], the characteristic oscillatory line shape of the RAS signal in the Soret band region, observed on LB samples after a certain critical coverage value [11], is explained in terms of dipole interactions between the porphyrin molecules arranged in an ordered lattice onto the substrate. The total lineshape results by adding the contribution of the single layers, in turn depending upon the orientation of the molecules in the layer, due to the interaction with the other molecules.…”

Section: Resultsmentioning

confidence: 99%

“…The interacting-dipoles model [12,13], although capable to describe the experimental results, is subject to a main criticism: all the values of the structural parameters characterizing the physical system are obtained phenomenologically, and not by first principles calculation (that probably represents a task too complicated to be performed at this stage). This means that the quality of the final result (exhibiting a nice agreement with experiment) should be relaxed, unless some independent argument is found to strengthen the main hypothesis.…”

Section: Resultsmentioning

confidence: 99%

“…Very recently, a new phenomenological model has been proposed to explain this RAS behaviour [12,13]: each LB layer is modelled as an ordered array of dipoles, and the dipole-dipole interaction is treated within the local fields theory. The resulting anisotropy spectrum for a given layer depends upon two parameters defining the average orientation of the molecules: the tilt angle θ (defined with respect to the normal to the substrate plane) and the azimuthal angle φ.…”

Section: Originalmentioning

confidence: 99%

See 2 more Smart Citations

Optical anisotropy and gas sensing properties of ordered porphyrin films

Bussetti

Corradini

Goletti

et al. 2005

Physica Status Solidi (b)

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Ordered films of porphyrins are routinely obtained by Langmuir-Blodgett technique, with a thickness control at the level of a single monolayer. The study of their optical anisotropy by reflectance anisotropy spectroscopy (RAS) has evidenced an interesting modification of the spectral line shape around the Soret band of the porphyrin layer after a certain critical thickness has been deposited onto the substrate. This finding has been connected to a structural modification of the film, although a detailed model was lacking until now. Recently, a new theoretical study based on the local field interaction has proposed to explain the RAS spectra in terms of the orientation of the molecules in a layer, that would change from layer to layer as the system is assembled. In order to test the model, we have collected new experimental data studying the modification of the optical anisotropy during exposure of the film to a gas (ethanol), mimicking the application for gas sensing analysis. The results show that the model is adequate to describe the real system: reordering of the layer during or after growth originates the anomalous spectra

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Originalmentioning

confidence: 99%

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Optical anisotropy and gas sensing properties of ordered porphyrin films

Bussetti

Corradini

Goletti

et al. 2005

Physica Status Solidi (b)

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“…Ab initio nonlinear calculations are even more computationally expensive, involving additional summations over intermediate states, and even bulk calculations have had limited success [74]. Alternative theoretical approaches have been reviewed [75] and, recently, interest has increased in polarizable dipole [76] and polarizable bond [77] models of the nonlinear optical response. Aspnes and co-workers have proposed a simplified bond hyperpolarizability model, where it was assumed that only the axial component of the bond hyperpolarizability contributes to the nonlinear response [78], and have recently extended this by including transverse components and higher-order effects [79].…”

Section: Theorymentioning

confidence: 99%

Probing surface and interface structure using optics

McGilp

2010

J. Phys.: Condens. Matter

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Optical techniques for probing surface and interface structure are introduced and recent developments in the field are discussed. These techniques offer significant advantages over conventional surface probes: all pressure ranges of gas-condensed matter interfaces are accessible and liquid-liquid, liquid-solid and solid-solid interfaces can be probed, due to the large penetration depth of the optical radiation. Sensitivity and discrimination from the bulk are the two challenges facing optical techniques in probing surface and interface structure. Where instrumental improvements have resulted in enhanced sensitivity, conventional optical techniques can be used to characterize heterogeneous adsorbed layers on a substrate, often with sub-monolayer resolution. Nanoscale lateral resolution is possible using scanning near-field optics. A separate class of techniques, which includes reflection anisotropy spectroscopy, and nonlinear optical probes such as second-harmonic and sum-frequency generation, uses the difference in symmetry between the bulk and the surface or interface to suppress the bulk contribution. A perspective is presented of likely future developments in this rapidly expanding field.

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“…Since the bulk optical properties of cubic crystals are isotropic, any observed anisotropy must be related to the lower symmetry of the surface and/or the adsorbed overlayer. We use a polarizable dipole model [11] to describe the response of each adatom and we assume that the substrate may be described as a homogeneous semiinfinite system described by a local dielectric function. For concreteness, we concentrate our attention on ordered alkali overlayers adsorbed on a (001) nominally isotropic metallic surface, and in particular, we consider the case of K atoms on a clean Ir(001) surface.…”

mentioning

confidence: 99%

Dipole model for the linear response of adsorbed overlayers

Vázquez-Nava

Arzate

Mejía

et al. 2008

Phys. Status Solidi (c)

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This paper present theoretical calculations of reflectance anisotropy spectra (RAS) for overlayers of alkali atoms adsorbed on a crystalline metallic surface. We assume that the overlayer is formed by an ordered twodimensional (2D) array of adatoms that respond to the local electric field like point‐like harmonic oscillators. We consider overlayers with several rational coverages, assuming that the adsorbates occupy high symmetry sites which form a Bravais lattice that is commensurate with the substrate [1,2]. RAS spectra are obtained for the five 2D Bravais lattices. We found that RAS can be used to observe ordered phases when the ordered phase has a rectangular, centered‐rectangular or oblique symmetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Polarizable dipole models for reflectance anisotropy spectroscopy: a review

Abstract: We present a review of the formalism and application of polarizable dipole models that have been used to calculate reflectance anisotropy spectra of semiconductor and metal surfaces and thin organic films.

Cited by 14 publications

References 89 publications

Optical anisotropy and gas sensing properties of ordered porphyrin films

Optical anisotropy and gas sensing properties of ordered porphyrin films

Probing surface and interface structure using optics

Dipole model for the linear response of adsorbed overlayers

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