Transitional Buffering Film

COMPOSITION-GRADED TRANSITIONAL BUFFERING FILM/ELECTROCOPPER... 

Figure 21.8 XPS spectra of the surface of composition graded transitional buffering film layered by double-graded process curve a, surface curve b, 1 min sputter curve c, 5 min sputter curve d, oxidized copper surface.

Figure 21.9 The proposed seetional model of a eomposition-graded transitional buffering film layered by double-graded proeess A, pure methane plasma polymer layer B, composition-graded layer of methane plasma polymer and metal C, sputtered metal layer with earbon contamination.

It was reported recently [216] that optical-quality PbTe thin films can be directly electrodeposited onto n-type Si(lOO) substrates, without an intermediate buffer layer, from an acidic (pH 1) lead acetate, tellurite, stirred solution at 20 °C. SEM, EDX, and XRD analyses showed that in optimal deposition conditions the films were uniform, compact, and stoichiometric, made of fine, 50-100 nm in size, crystallites of a polycrystalline cubic structure, with a composition of 51.2 at.% Pb and 48.8 at.% Te. According to optical measurements, the band gap of the films was 0.31 eV and of a direct transition. Cyclic voltammetry indicated that the electrodeposition occurred via an induced co-deposition mechanism. 

Fig. 23 Equilibrium spreading pressures of (R,S)-( +)- and(R)-( +)-stearoyltyrosine on an aqueous subphase of pH 6.86 (potassium phosphate/disodium phosphate buffer) as a function of temperature. Film type II is the film at temperatures above the transition and film type I is the film at temperatures below the transition. Reprinted with permission from Arnett et al, 1990. Copyright 1990 American Chemical Society.

Fig. 9. Effect of solution pH on the redox behavior of an Ru02 aqueous solution interface. (— -), From work with an Ru02/Ti02 film [209]. The upper lines are for the Ru(IV)/Ru(VI) transition as obtained from voltammograms for pure RuOz (on Ti) in a range of borate (pH > 8) and phthalate (pH < 8) buffer solutions O and refer to the cathodic and anodic peak maxima respectively. (- -), Variation of the half-wave potential for benzaldehyde oxidation (O.lmoldm-3, scan rate = 1.5mVs 1) on pure Ru02 in buffered 10% f-butanol in water mixtures. The voltammograms outlined on the left and right for Ru02 in acid and base, respectively [207],...

Other properties of fatty acid monolayers such as the phase transition temperature are consistent with the field strength theory stearic acid monolayers formed rigid films on alkaline earth subphases (17, 35). The temperature of the phase transition from rigid to fluid monolayers, estimated by the Devaux talc test, was a function of pH and buffer composition (Figure 17). Thus transition temperature at pH 6 decreased in a weak field sequence (I in Table III) while transition temperatures at pH 8 decreased in an intermediate field sequence (III or IV in Table III). Since variables such as tt are not controlled in these experiments, it is surprising that transition temperature data followed these sequences. 

Brinker and coworkers also monitored the absorbance (A) at 355 nm (it it transition) in situ to ealeulate the kinetics of the ds trans isomerization of the azobenzene ligands contained in the nanocomposite film deposited on the ITO/ glass substrate in buffer solution (Liu, 2004). The first-order plot o ln Aao, Aq)/ (Aao—At)) vs. t was not perfectly linear in the entire region. The slope (rate constant, k) gradually decreases (t< 250 min) and remains constant (t> 250 min). The deviation from first-order kinetics is common for azobenzene ligands confined in sol-gel matrices or polymers (Bohm et al., 1996 Ueda et al., 1992). These data imply that the kinetics is composed of two parts, a fast one (ki) and a slow one ( 2). When t is small, the fast proeess is predominant. On the contrary, the slow process becomes predominant as time (i) increases. A double exponential equation was used to fit the data and evaluate ki and k2-... 

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