Specular X-ray reflection

Instrumentation. In most studies reported so far. X-ray radiation of a synchrotron collimated and monochromatized with suitable optics is used. An electrochemical cell with a moving working electrode is employed in order to minimize X-ray absorption by the electrolyte solution. A typical cell design is depicted in Fig. 6.10. 

For electrochemical measurements, the electrode is lowered away from the Mylar film that serves as a cell cover and X-ray window. After moving the electrode upwards, an electrolyte solution film of about 10 pm remains with only small radiation absorption. 

The surface-normal structure of epitaxially grown Te and Cd upd-layer was studied [89] and other upd-systems have been the subject of investigations [33, 88]. Kinetic studies of passive oxide formation on iron and iron alloys [90] and of Au(OOl) reconstruction have been reported [73]. 

Robinson, in Spectmscopic and Diffraction Techniques in Interfacial Electrochemistry, ed. by C. Gutierrez, C. Melendres. NATO ASI Series C, vol. 320 (Kluwer Academic, Dordrecht, 1990), p. 313 

Crystal Structure Analysis (Oxford University Press, Oxford, 2001) 

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Reflectometry is a useful probe with which to investigate the structure of multilayers both in self-supporting films and adsorbed on surfaces [51]. Specular X-ray reflectivity probes the electron density contrast perpendicular to the film. The X-rays irradiate the substrate at a small angle (<5 °) to the plane of the sample, are reflected, and are detected at an equal angle. If a thin film is present on the surface... 

A Specular X-ray reflection While the specular X-ray reflection (SXR) approach is again a means of probing solid coatings at the atomic level, it does have the advantage that the model obtained at the surface can include information on the atomic-scale roughness of the buried , i.c. usually inaccessible, electrode/surface layer interface. 

Figure 9.2 Scattering geometries with the corresponding initial and final wave vector and kj. (a) Setup for specular X-ray reflectivity measurements which reveal the sample stracture (roughness, lattice spacing) along the surface normal.

Thermal expansion of thin (130-5 nm) PHOST films coated on various substrates has been measured by using specular X-ray reflectivity [487]. Complementary use of neutron and X-ray reflectometry has allowed one to measure the spatial evolution of the reaction front in the fBOC resist with nanometer resolution [499]. Using a bilayer geometry with a lower layer consisting of PHOST protected with COO(CD3)3 and an upper layer consisting of PHOST containing PAG, compositional and density depth profiles were measured. 

Instrumentation. The electrochemical cells described in the preceding section can be used. A cell design with a significantly reduced radiation absorption of the electrolyte solution film as used for specular X-ray reflectivity measurements (see description below Fig. 6.10) can also be used. Electrode potentials are selected based on standard electrochemical experiments (e.g. cyclic voltammetry) with respect to well-defined changes of the electrode-solution interface (e.g. potential steps between potentials of complete desorption and maximum adsorption). Control of the potentiostat and the X-ray diffractometer as well as data acquisition, storage and manipulation are done with a suitably programmed computer. 

Key words grazing-incidence X-ray diffraction, specular X-ray reflectivity, liquid surface X-ray scattering, advanced materials, thin films, lipid structure, lipid-protein interactions. 

Specular X-ray reflectivity (XR) data for monolayers of the pure lipids DPG and MOG are shown in Figure 9C. Two-slab models were refined to the measured data (points) and the resulting calculated reflectivity curves are shown as lines in Figure 9C. The parameters of the... 

Chason E, Mayer TM (1997) Thin film and surface characterization by specular X-ray reflectivity. Crit Rev Solid State Mater Sci 22 1-67... 

The changes in enthalpy that occur at the LCOT of a P( /-S-f>-nBMA) copolymer (Mw=85K) were measured using differential scanning calorimetry (DSC). The volume change of the transition was determined by specular x-ray reflectivity measurements of the copolyma as a function of temperature. From the Kiessig fringes in the reflectivity profile, the thickness of the sample can be determined very... 

Figure 24-14. Off-specular X-ray reflectivity patterns showing the time-dependent growth of the first order diffraction peak for mesophase silica-surfactant films grown at the surface of a dilute acidic solution with a TMOS/CuTABr molar ratio of (a) 10.87 and (b) 7.25. At the higher TMOS/CuTABr ratio the film grows at the surface by addition of silica-coated surfactant micelles so the diffraction peak becomes narrower as the domains grow into solution, and more intense as the interface is covered. At the intermediate TMOS/Cu TABr ratio the film grows by packing at the interface of mesostructured particles formed in the bulk solution so the peak widtii does not change, but the intensity increases as the interface is covered.

Soles, C., Douglas, J., Wu, W., Peng, H., Gidley, D. Comparative specular x-ray reflectivity, positron annihilation lifetime spectroscopy, and incoherent neutron scattering measurements of the dynamies in thin polycarbonate films. Macromolecules 37(8), 2890-2900 (2004)... 

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