Interface Films

When infrared radiation with electric field amplitude Eo impinges on the film-covered substrate, some is reflected from the ambient/film interface while some is transmitted into the film and then reflected at the film/substrate interface. Some of the radiation reflected at the film/substrate interface is reflected back into the film at the film/ambient interface. However, some is transmitted into the ambient (see Fig. 4). The reflection coefficient (r) for the film/substrate system is calculated by summing the electric field amplitudes for all of the waves reflected into the ambient and then dividing by the electric field amplitude Eo) of the incident radiation. 

C.G. Vayenas, R.M. Lambert, S. Ladas, S. Bebelis, S. Neophytides, M.S. Tikhov, N.C. Filkin, M. Makri, D. Tsiplakides, C. Cavalca, and K. Besocke, Direct STM, XPS and TPD observation of spillover phenomena over mm distances on metal catalyst films interfaced with solid electrolytes, Stud. Surf. Sci. Catal. 112, 39-47 (1997). 

S. Neophytides, D. Tsiplakides, and C.G. Vayenas, Temperature-Programmed Desorption of Oxygen from Pt-films Interfaced with Y203-Doped Zr02> /. Catal. 178, 414-428 (1998). 

D. Tsiplakides, S. Neophytides, and C.G. Vayenas, Investigation ofthe state ofthe electrochemically generated adsorbed O species on Au films interfaced with Y203-doped-ZrOj, Ionics, submitted (2001). 

A subsequent detailed XPS study of Pt films interfaced with YSZ6 (Figs 5.35 to 5.37) has shown that ... 

Figure 6.7. Example of rule G2 (electrophilic behaviour) Effect of Pc2h4(= Pd) (a), Po2 (=Pa) (b) and A (c) on the rate of C2H4 oxidation on Pt films interfaced with CaZrO 9ln01O3.aj a H+-conductor.50 Note that Fig. 6.7c is obtained under gaseous composition where the rate is positive order in 02 and negative order in C2H4 (Figs. 6.7a, 6.7b). Reprinted with permission from the Institute for Ionics.

Methanol oxidation on Ag polycrystalline films interfaced with YSZ at 500°C has been in investigated by Hong et al.52 The kinetic data in open and closed circuit conditions showed significant enhancement in the rate of C02 production under cathodic polarization of the silver catalyst-electrode. Similarly to CH3OH oxidation on Pt,50 the reaction exhibits electrophilic behavior for negative potentials. However, no enhancement of HCHO production rate was observed (Figure 8.48). The rate enhancement ratio of C02 production was up to 2.1, while the faradaic efficiencies for the reaction products defined from... 

G. Pitselis, P. Petrolekas, and C.G. Vayenas, Electrochemical Promotion of NH3 decomposition over Fe catalyst films interfaced with K+ and Na+ conductors, Ionics 3, 110-117(1997). 

Charge propagation within the film is in principle slower than charge injection (or consumption) at the electrode/film interface Whether electrons are transported... 

In recent years, high-resolution x-ray diffraction has become a powerful method for studying layered strnctnres, films, interfaces, and surfaces. X-ray reflectivity involves the measurement of the angnlar dependence of the intensity of the x-ray beam reflected by planar interfaces. If there are multiple interfaces, interference between the reflected x-rays at the interfaces prodnces a series of minima and maxima, which allow determination of the thickness of the film. More detailed information about the film can be obtained by fitting the reflectivity curve to a model of the electron density profile. Usually, x-ray reflectivity scans are performed with a synchrotron light source. As with ellipsometry, x-ray reflectivity provides good vertical resolution [14,20] but poor lateral resolution, which is limited by the size of the probing beam, usually several tens of micrometers. 

Simulation of the RBS experimental spectra by means of the RUMP code has shown that, in both cases, the film composition was Fe203 (within 5%). The spectra also confirm the sharp character of the substrate/film interface, within the resolution... 

Continuous (barrier, passivation) films have a high resistivity (106Q cm or more), with a maximum thickness of 10 4cm. During their formation, the metal cation does not enter the solution, but rather oxidation occurs at the metal-film interface. Oxide films at tantalum, zirconium, aluminium and niobium are examples of these films. 

The results demonstrated that both compression and shear can induce the formation of C-C bonds between sp-hybridized carbons atoms, which leads to polymerization within the SAM. Interestingly, it was found that the location of these reactive sites within the film could influence the calculated friction. For instance, if the diacetylene components in the chains were close to the tip/film interface, reactions between the film and tip could occur, which led to wear and high friction. On the other hand, if the diacetylene moieties were far from the tip, the reactions did not lead to wear and had little effect on the average calculated friction. These observations demonstrate that a proper treatment of the chemical reactivity of the system may be necessary in some cases to calculate friction accurately. 

The structural state of dendritic macromolecules at air-water (Langmuir mono-layers) and air-solid (adsorbed monolayers, self-assembled films and cast films) interfaces have been reviewed by Tsukruk [17]. Although this work summarizes various characterization techniques for dendritic films by AFM techniques, in this chapter, we will present recent progress on the characterization of the dendritic film surface morphologies. 

E. H. Hellen and D. Axelrod, Fluorescence emission at dielectric and metal-film interfaces,... 

We examine an electron transfer of hydrated redox particles (outer-sphere electron transfer) on metal electrodes covered with a thick film, as shown in Fig. 8-41, with an electron-depleted space charge layer on the film side of the film/solution interface and an ohmic contact at the metal/film interface. It appears that no electron transfer may take place at electron levels in the band gap of the film, since the film is sufficiently thick. Instead, electron transfer takes place at electron levels in the conduction and valence bands of the film. 

Thus, in the stationary state, the rate of anodic transfer of metal ions across the metal/film interface equals the rate of anodic transfer of metal ions across the film/solution interface this rate of metal ion transfer represents the dissolution rate of the passive film. The thickness of the passive film at constant potential remains generally constant with time in the stationary state of dissolution, although the thickness of the film depends on the electrode potential and also on the dissolution current of the passive film. 

Figure 2.12 shows the Cp values resulting from fitting peak potentials measured in CV as a function of ionic strength with Equation 2.5 for PAH-Os/PVS films finished either in positive or negative polyions and assembled and tested at different pHs. Interestingly, not always do films finished in PVS have Cp < 0 and films capped with PAH-Os have Cp>0, which means that uncompensated charges at the electrolyte/ film interface are not the only contribution to Cp. The other contribution arises from... 

---