Films, oxide thickness

Formation conditions Nature of oxide film Thickness (nm)... 

For control or calibration purposes, film thickness can be determined by mounting a sectioned specimen and measuring the oxide film thickness directly on the screen of a projection microscope at a known magnification. Alternatively, the loss in weight of an anodised sample of known area may be found after the film has been stripped in a boiling solution made up as follows ... 

Sample surface unrepresentative. Heterogeneity of the sample was given above as the cause of Class II deviations. The case in which heterogeneity causes one part of a surface to differ from another is clear enough it is often encountered with minerals. Here we wish to direct attention to cases where a surface, though uniform, differs in composition from the bulk of the sample. The cause may be an oxide film thick enough that composition differences between it and the bulk of the sample influence the analytical results. 

Damjanovic A, Hudson PG. 1988. On the kinetics and mechanism of O2 reduction at oxide film covered Pt electrodes. I. Effect of oxide film thickness on kinetics. J Electrochem Soc 135 2269-2273. 

The capacitance determined from the initial slopes of the charging curve is about 10/a F/cm2. Taking the dielectric permittivity as 9.0, one could calculate that initially (at the OCP) an oxide layer of the barrier type existed, which was about 0.6 nm thick. A Tafelian dependence of the extrapolated initial potential on current density, with slopes of the order of 700-1000 mV/decade, indicates transport control in the oxide film. The subsequent rise of potential resembles that of barrier-layer formation. Indeed, the inverse field, calculated as the ratio between the change of oxide film thickness (calculated from Faraday s law) and the change of potential, was found to be about 1.3 nm/V, which is in the usual range. The maximum and the subsequent decay to a steady state resemble the behavior associated with pore nucleation and growth. Hence, one could conclude that the same inhomogeneity which leads to pore formation results in the localized attack in halide solutions. 

If measurements are made in thin oxide films (of thickness less than 5 nm), at highly polished Al, within a small acceptance angle (a < 5°), well-defined additional maxima and minima in excitation (PL) and emission (PL and EL) spectra appear.322 This structure has been explained as a result of interference between monochromatic electromagnetic waves passing directly through the oxide film and EM waves reflected from the Al surface. In a series of papers,318-320 this effect has been explored as a means for precise determination of anodic oxide film thickness (or growth rate), refractive index, porosity, mean range of electron avalanches, transport numbers, etc. 

Figure 3.12 (a) Steady state values of A and 1 as a function of potential. Platinum in aqueous sulphuric acid. (b> Dependence of oxide film thickness on potential. Platinum in aqueous sulphuric acid. From Reddy et a . (1968). 

Such reactions processes are responsible for the transition from PS formation to electropolishing with increasing potential as typically revealed in an i-V curve.18 PS formation can occur when the surface is not or only partially covered by oxide. Once the whole surface is covered with an oxide film further reaction can only proceed through the formation of oxide followed by its dissolution. Further increasing the potential will only result in an increase of oxide film thickness. On the other hand, increasing HF concentration will increase the dissolution rate of oxide. The presence of oxide on the silicon surface in the PS formation region and its increase with potential have been experimentally observed.98... 

Factors controlling nanostructure and oxide film thickness... 

Fig. 38. Dependence of electroreflection amplitude on the potential for the silicon electrode. ha> = 3.42 eV the oxide film thickness (nm) 1—120 2—35 3—17. [From Tyagai and Snitko (1980).]...

Figure 7-1. Possible oxidation mechanisms related to oxide film thicknesses, overview.

An important consequence of the zone equilibrium approximation is that the quantities Cx (5 ) and CX(L ) appearing in the above expressions can be viewed as constants independent of oxide film thickness L. In this limit... 

Fig. 28. Dependence of limiting oxide film thickness on temperature. [After Rhodin, J. Am, Chem. Soc. 73, 3143 (1951).]...

Since diffusion is thermally activated, the growth rate in oxide film thickness during sliding as a function of temperature, similar to thermal oxidation under static conditions, follows an Arrhenius type of relationship... 

The formation of a rare earth metal oxide on the metal surface, impedes the cathodic reduction of oxygen and thus cathodic inhibition is achieved by the addition of a rare earth metal salt to a system. The surface atom concentration ratio, [Ce/Ce + M], where M is Fe, Al or Zn, is a function of cerium oxide film thickness determined by AES depth profiles as shown in Fig. 12.2. 

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