Mass thickness

In another approach, which was previously mentioned, the mass thickness, or depth distribution of characteristic X-ray generation and the subsequent absorption are calculated using models developed from experimental data into a < )(p2) function. Secondary fluorescence is corrected using the same i flictors as in ZAP. The (pz) formulation is very flexible and allows for multiple boundary conditions to be included easily. It has been used successfully in the study of thin films on substrates and for multilayer thin films. 

Attenuation Coefficient—The fractional reduction in the intensity of a beam of radiation as it passes through an absorbing medium. It may be expressed as reduction per unit distance, per unit mass thickness, or per atom, and is called the linear, mass, or atomic attenuation coefficient, respectively. 

To determine the thickness of a thin layer, the composition and the density of the sputtered layer should be exactly known. The partial mass thickness cxDx must be divided by cx (the concentration of the analyte in the thin layer) to determine the total mass thickness Dx. Division of Dx by the density of the thin layer gives the thickness of the thin layer expressed in units of length. In their thickness calculations, De Neve et al. (2000) assumed their TiOx layers to be Ti02 with a density of 4.26gem-3. ... 

Results obtained by CPAA for composition and partial mass thickness have been shown to be consistent with the results obtained via other analytical methods. The main advantage of the use of CPAA as a surface characterization method are its purely instrumental character, requiring no sample preparation, its high accuracy, and its low detection limits. 

In a thin specimen, the magnitude of Ia is proportional to the mass thickness, pt ... 

Figure 2.54 The geometry of one of the substrates employed by Murray and Allara in their spacer experiments. PMMA = polymelhyl methacrylate spacer of thickness J, PNBA = monolayer of p-nitrobcnzoic acid. The mass thicknesses of the other layers are CaF, = 800 A. Al = 2500 A. Al = oxide c. 30 A, Ag = 200 A. From Murray and Allara (1982).

If the effect of absorption can not be neglected in the sample, the ratio of measured intensities contains the ratio of two exponentials from Beer s law. It corresponds to a difference inside the exponential. In practice, it is the mass absorption coefficients (ju/p) and the absorption path lengths expressed in mass thickness (pL) that are used. 

Barer R (1953) Determination of dry mass, thickness, solid and water concentration in living cells Nature 172 1098... 

QCM-D measurements that include dissipation allow a more accurate estimate of mass changes through application of Voigt model that takes into account the viscoelastic properties of the system. Modeling software QTools supphed by Q-Sense uses the full thick layer expressions to model the response. Here, this program has been used to estimate the mass, thickness, viscosity, and shear elastic modulus of the adsorbed pectin layer on BSA surface, with a best fit between the experimental and model/and D values. 

The transmission electron microscope (TEM) image from crazes in such films, the negative from which Fig. la was printed, can be analyzed not only to reveal dimensions of the craze but also to yield the local craze fibril volume fraction v by using a microdensitometer to measure the local density of the image, its mass thickness contrast The extension ratio of the craze fibrils, X equals i. ... 

Substrates for surface-enhanced Raman scattering (SERS) were prepared by vapor deposition of silver directly onto the surface of porous alumina. Silver nanostructures have been characterized by SEM and UV-Vis absorption. The SERS-activity of the substrates tested with water-soluble cationic Cu-porphyrin as a probe molecule, attained the maximum when Ag mass thickness vtas approximately 60 nm. 

In preliminary experiments we have shown that silver films thermally evaporated onto AAO substrates spontaneously form ordered nanocrystal arrays. In the present study we have prepared a series of Ag-coated AAO substrates with different silver mass thickness, and we have determined the optimum thickness of Ag film for SERS by observing the spectra of water-soluble cationic Cu(II)-tetrakis(4-N-methylpyridyl) porphyrin (CuTMpyP4). 

The AAO substrates with uniform and parallel nanoporous structure were prepared in a two-step electrochemical anodization of aluminum foils in 4 % oxalic acid, at the constant current density of 3 A/dm, during 60 min. The pore diameter and average interpore spacing were 40 5 nm and 120 20 nm, correspondingly. The arrays of Ag nanoparticles on AAO were formed by thermal evaporation of silver onto a AAO substrate at room temperature. The mass thickness of silver was varied by varying the deposition time. Two series of samples with thickness 30, 60, 90, 120, 150 and 180 nm were prepared. 

To examine the dependence of the Raman signal on Ag film thickness, the intensity of the band 1350 cm in SERS spectra of CuTMpyP4 for two series of samples was plotted as a function of the mass thickness. The results are presented in Fig. 3. 

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