X ray reflectivity

In 2006, the first x-ray reflectivity study of an ITIES was published in a series of papers by Luo et al. [68-70]. They studied an interface between a nitrobenzene solution of tetrabutylammonium tetraphenylborate (TBATPB) and an aqueous solution of tetrabutylammonium bromide (TBABr). The concentration of TBABr was varied to control the Galvani potential difference using an experimental setup as shown in Eigure 1.4. The ion distributions were predicted by a Poisson-Boltzmann equation, that explicitly includes a free energy profile for ion transfer across the interface described either by a simple analytic form or by a potential of mean force from molecular dynamics simulations. 

Reflectometry is a useful probe with which to investigate the structure of multilayers both in self-supporHng 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 smaU 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 

---

The actual structure at a vapor-liquid interface can be probed with x-rays. Rice and co-workers [72,73,117] use x-ray reflection to determine the composition perpendicular to the surface and grazing incidence x-ray diffraction to study the transverse structure of an interface. In a study of bismuth gallium mixtures. 

The detailed examination of the behavior of light passing through or reflected by an interface can, in principle, allow the determination of the monolayer thickness, its index of refiraction and absorption coefficient as a function of wavelength. The subjects of ellipsometry, spectroscopy, and x-ray reflection deal with this goal we sketch these techniques here. 

The development of scanning probe microscopies and x-ray reflectivity (see Chapter VIII) has allowed molecular-level characterization of the structure of the electrode surface after electrochemical reactions [145]. In particular, the important role of adsorbates in determining the state of an electrode surface is illustrated by scanning tunneling microscopic (STM) images of gold (III) surfaces in the presence and absence of chloride ions [153]. Electrodeposition of one metal on another can also be measured via x-ray diffraction [154]. 

The monolayer density, as measured by x-ray reflectivity, is only - 90% of the value of a crystalline paraffin such as suggesting a significant... 

The film thickness of epitaxial and highly textured thin films can be measured with XRD. Close to the usual or primary difftaction peaks there are secondary or subsidiary maxima in the difftacted intensity (see Figure 6), which are due to the finite film thickness. The film thickness is inversely proportional to the spacing between these maxima and is easily calculated. X-ray reflectivity is another accurate method for measuring a film s thickness. 

Fig. 8. X-ray reflection diagram of a thin polystyrene film on float glass [160]. The reflectivity R is plotted against the glancing angle . The film is spin coated from solution. A model fit (dashed line) to the reflectivity data is also shown where the following parameters are obtained film thickness = 59.1 0.1 nm, interface roughness glass-polymer = 0.4 0.1 nm, surface roughness polymer-air = 0.6+1 nm, mean polymer density = 1.05 + 0.01 g/cm-3. The X-ray wavelength is 0.154nm...

Fig. 10. X-ray reflectivity curves of polystyrene (PS)/poly-p-bromostyrene (PBrS) on a glass substrate before (solid line) and after annealing for 13 h at 130 °C (dashed tine) [191]. The width of the interface changes from 1.3 nm to 2.0 nm due to interfacial mixing of components. The X-ray wavelength is 0.154 nm and films have a thickness of 37.8 nm (PS) and 45.0 nm (PBrS), respectively...

Table 11. X-ray reflection data for -y-brass (CvuZna) and calculated electron densities.

---