Topic
X-ray reflectivity
About: X-ray reflectivity is a research topic. Over the lifetime, 2215 publications have been published within this topic receiving 37648 citations.
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TL;DR: MOTOFIT as mentioned in this paper uses a slab-model approach with the Abeles matrix method, and extensions for surface roughness to perform nonlinear least-squares regression on the experimental reflectivity curves.
Abstract: The contrast-variation technique is employed in multiple-contrast neutron/X-ray reflectometry experiments to highlight scattering from different structural components that are present at a surface or interface. The advantage of this technique is that the structural model used to describe the interfacial scattering length density profile must apply to all the contrasts measured. A new reflectivity analysis package, MOTOFIT, which runs in the IGOR Pro environment (http://www.wavemetrics.com), has been created to aid the simultaneous fitting (with the same structural model) of these multiple-contrast data, using an intuitive graphical user interface, which most co-refinement packages do not possess. MOTOFIT uses a slab-model approach with the Abeles matrix method, and extensions for surface roughness to perform non-linear least-squares regression on the experimental reflectivity curves. Other features, such as the ability to create complicated interparameter constraints or analyse reflectivity from multilayers, simulated annealing, etc., make MOTOFIT a powerful reflectometry analysis package
959 citations
IBM1
TL;DR: The use of X-ray and neutron reflectivity to study polymers in the condensed state and in solutions is revieved in this article, where basic theoretical and experimental concepts of specular reflectivity are presented.
736 citations
TL;DR: In this paper, a new ellipsometry technique was developed for the measurement of the dielectric constants of high reflectivity metals, which is especially well suited to the measurements of high-reflectivity metals.
Abstract: We report the development of a new ellipsometry technique which is especially well suited to the measurement of the dielectric constants of high reflectivity metals. Modulation methods are used to permit the measurement of a differential reflectance parameter which does not decrease in sensitivity in the high reflectivity limit as do the usual reflectance parameters measured with standard techniques. In addition the ellipsometer is faster than previous methods, being capable of recording the relevant data in a few minutes as the wavelength is swept continuously over a range of several thousand angstroms. The precision of the dielectric constants so measured is 1% in most cases. The polarization modulation technique, upon which the ellipsometer is based, is presented in detail, with emphasis on its wider applicability to any problem involving the study of dichroic phenomena.
532 citations
TL;DR: In this paper, an interband effective electron mass was defined for carbon systems, where the mass density was derived from the valence electron density via the plasmon energy, which is measured by electron energy-loss spectroscopy (EELS).
Abstract: Grazing-angle x-ray reflectivity (XRR) is described as an efficient, nondestructive, parameter-free means to measure the mass density of various types of amorphous carbon films down to the nanometer thickness range. It is shown how XRR can also detect layering if it is present in the films, in which case the reflectivity profile must be modeled to derive the density. The mass density can also be derived from the valence electron density via the plasmon energy, which is measured by electron energy-loss spectroscopy (EELS). We formally define an interband effective electron mass ${m}^{*},$ which accounts for the finite band gap. Comparison of XRR and EELS densities allows us to fit an average ${m}^{*}=0.87m$ for carbon systems, m being the free-electron mass. We show that, within the Drude-Lorentz model of the optical spectrum, ${m}^{*}=[1\ensuremath{-}{n(0)}^{\ensuremath{-}2}]m,$ where $n(0)$ is the refractive index at zero optical frequency. The fraction of ${\mathrm{sp}}^{2}$ bonding is derived from the carbon K-edge EELS spectrum, and it is shown how a choice of ``magic'' incidence and collection angles in the scanning transmission electron microscope can give ${\mathrm{sp}}^{2}$ fraction values that are independent of sample orientation or anisotropy. We thus give a general relationship between mass density and ${\mathrm{sp}}^{3}$ content for carbon films.
511 citations
TL;DR: In this article, it has been demonstrated that repeated dipping of the substrate into solutions of polycations and polyanions in an alternating sequence leads to the deposition of continuous molecular layers that form a polymer film with a well-defined supramolecular structure.
Abstract: Ultrathin polymer films were physisorbed to surface-modified Si wafers by electrostatic deposition of polyelectrolytes from aqueous solutions. For the first it has been demonstrated that the preparation procedure, which involves repeated dipping of the substrate into solutions of polycations and polyanions in an alternating sequence, leads to the deposition of continuous molecular layers that form a polymer film with a well-defined supramolecular structure
452 citations