Diffusion depth, determination

Fig. 3 a - c. Schematic diagram illustrating the decreasing source method for diffusion transport determination of any organic pollutant in solution or leached from complex mixtures, as follows a column setup b pollutant concentration vs time in source and collection reservoirs during the test c pollutant concentration in solid-pore water with depth from source after the test... 

The F uptake of flint takes a much longer time than that for bone. Fluorine diffusion into the depth of flint material is controlled by defect clusters. The diffusion coefficient determined by implanting a model compound (amorphous silica bombarded with heavy ions and hydrated at 100°C) is 9.10—21 cm2/s at room temperature. The corresponding penetration depth of F under ambient conditions in a 1000-year-old artefact can be estimated via x — (Dt)1/2 = 0.17. im [50], Thus, F accumulates only in the first micrometre of the surface. The surface of ancient flint artefacts can be altered by dissolution. The occurrence of this phenomenon is especially important in basic media. However, in some cases, the thickness of the dissolved layer can be neglected compared to the F penetration depth at low temperatures. Therefore, Walter et al. [35] proposed relative dating of chipped flint by measuring the full width at half maximum (FWHM) of F diffusion profiles in theses cases. 

The Fe was diffused, from a spin-on glass film, onto n-type wafers at 700 to 900C. The diffusivities, as determined using junction-depth and conductivity techniques, could be explained in tenns of a model which assumed the existence of exhaustible diffusion sources. It was found that the diffusivity was described by ... 

A common technique is to deposit a very thin film of radioactive isotopes on a plane surface of a sample, and, after subsequent diffusion anneal, determine the activity of diffusion species as a function of distance from the plane surface. If the thickness of the sample is very much larger than the penetration depth of the tracers, the solid can be considered semi-infinite. Furthermore, if the diffusion is homogenous (e.g. taking place by lattice diffusion), the concentration of the diffusing tracers normal to the plane is through solution of Fick s second law with appropriate boundary conditions given by... 

Also, through the XPS data, a limited diffusion of the dopant ions is indicated. The Ca atoms are not localized at the immediate surface but rather diffuse into the nearsurface region. Although it would be extremely difficult to determine an exact diffusion depth profile, it is obvious from the XPS(0) data that the Ca atoms are confined to within the depth observable by XPS. Therefore the upper and lower limits to the diffusion distance (which is undoubtedly not a sharp diffusion depth) are defined. In this way it can be estimated that the Ca atoms are distributed in some way within roughly 25 A of the surface of the DHPPV. 

Figure 3.11 Temperature dependence of Vitamin E Index ( ) and maximal diffusion depth after 24 h ( ) in UHMWPE (data at 130°C are neglected for determining the activation energy because of the change in diffusion and sorption induced by the start of melting transition).

We assume in the following that the ligand is bound in a binding pocket of depth 6 —a = 7 A involving a potential barrier AU = 25 kcal/mol, similar to that of streptavidin (Chilcotti et al., 1995). We also assume that the diffusion coefficient of the ligand is similar to the diffusion coefficient of the heme group in myoglobin (Z) = 1 A /ns) as determined from Mofibauer spectra (Nadler and Schulten, 1984). 

Diffusivities of various elements ate determined experimentally. Dopant profiles can be determined. The junction depth can be measured by chemically staining an angle-lapped sample with an HE/HNO mixture. The -type region of the junction stains darker than the n-ty e region. The sheet resistivity can also be measured using a four-point probe measurement. These two techniques ate used for process monitoring. 

Figure 7 Quantitative high depth resolution profile of the major elements in the thin-film structure of Al /TIN /Si, comparing the annealed and unannealad structures to determine the extent of interdiffusion of the layers. The depth profile of the unannealed sample shows excellent depth resolution (a). The small amount of Si in the Al is segregated toward the Al/TiN interface. After annealing, significant Ti has diffused into the Al layer and Al into the TIN layer, but essentially no Al has diffused into the Si (b). The Si has become very strongly localized at the Al / TIN interface.

Figure 3.27 shows the depth profile of such a layer. Enrichment of Ti and A1 at the layer-substrate interface is visible. The Si signal in the layer increases with depth. It will subsequently be shown that it is not possible to determine from the depth profile alone whether there is diffusion of Si into the CrN layer. 

The skin layers from the palm of the hand were scanned in vivo. A CPMG sequence was applied to sample the echo train decays as a function of depth. The decay was determined by both the relaxation time and the diffusion coefficient. To improve the contrast between the layers, a set of profiles was measured as a function of the echo... 

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