Studying textured films

We saw that studying thin films makes it necessary for the diffraction patterns to be produced at a fixed and controlled incidence. We will assume that we are conducting an experiment with this type of equipment and that we want to find out whether the film is textured or not. 

3 Other peaks ean appear if the ineidenee angle is such that other planes are approximately in the Bragg position, or if part of a film is comprised of randomly oriented grains. 

4 Aside from this intrinsic aspect of the sample, Bragg-Brentano systems usually are not equipped with a support that makes it possible to orient the sample accurately with respect to the diffractometer s frame of reference. Thus, an angular error in the positioning of the 

We described in detail the method for illustrating a non-random orientation of grains in a film. We are now going to continue by describing the methods for quantifying this orientation. 

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The angle 0h is the angle between the X-ray polarization direction, s, and the direction to the atom h in the j shell. For isotropic materials, like powders, the sum becomes N/3. For thin films like heteroepitaxial metallic films [19], there is often an intrinsic asymmetry leading to different in-plane and out-of-plane bonds. Otherwise, the polarization dependence of EXAFS can be also an important tool for studying texturized films providing an alternative probe to the long range order technique such as diffraction when XRD diffraction is dominated by that from the substrate. 

As we have already mentioned, this description of quantitative texture measurements based on pole figures involves both bulky samples and thin films. The experimental conditions may differ in order to optimize the diffracting volumes, but this has already been discussed in Part 1 of this book. We will not go into any further detail on the study of textured films since, most of the time, it can all be reduced to the general case of quantitative texture analysis. 

Thompson and Carol (1995) have experimentally studied texture evolution in Ag thin films and have shown that the competition between strain energy minimization and surface energy minimization leads to film textures that are consistent with the transition predicted by (1.32). Figure 1.38 shows their experimental results on texture evolution in Ag polycrystalline thin films of different thicknesses as a function of temperature excursion AT from the deposition temperature. Here, the Ag films were deposited on MgO(lOO) substrates coated with amorphous silicon oxide. The solid line in this figure denotes the texture transition condition predicted by (1.32). 

The determination of particle size and stmctural iaformation for fibers and polymers, and the study of stress, texture, and thin films are appHcations that are growing ia importance and can be examined with x-ray iastmments. 

X-ray diffraction consists of the measurement of the coherent scattering of x-rays (phenomenon 4 above). X-ray diffraction is used to determine the identity of crystalline phases in a multiphase powder sample and the atomic and molecular stmctures of single crystals. It can also be used to determine stmctural details of polymers, fibers, thin films, and amorphous soflds and to study stress, texture, and particle size. 

Cachet H, Cortes R, Froment M, Mamin G (1999) Epitaxial growth of electrodeposited cadmium selenide on (111) gallium arsenide. Philos Mag Lett 79/10 837-840 Muthuvel M, Stickney JL (2006) CdTe Electrodeposition on InP(lOO) via Electrochemical Atomic Layer Epitaxy (EC-ALE) Studies Using UHV-EC. Langmuir 22 5504-5508 Streltsov EA, Osipovich NP, Ivashkevich LS, Lyakhov AS (1999) Effect of Cd(ll) on electrodeposition of textured PbSe. Electrochim Acta 44 2645-2652 Beaunier L, Cachet H, Cortes R, Froment M (2000) Electrodeposition of PbSe epitaxial films on (111) InP. Electrochem Commun 2 508-510... 

Applications The general applications of XRD comprise routine phase identification, quantitative analysis, compositional studies of crystalline solid compounds, texture and residual stress analysis, high-and low-temperature studies, low-angle analysis, films, etc. Single-crystal X-ray diffraction has been used for detailed structural analysis of many pure polymer additives (antioxidants, flame retardants, plasticisers, fillers, pigments and dyes, etc.) and for conformational analysis. A variety of analytical techniques are used to identify and classify different crystal polymorphs, notably XRD, microscopy, DSC, FTIR and NIRS. A comprehensive review of the analytical techniques employed for the analysis of polymorphs has been compiled [324]. The Rietveld method has been used to model a mineral-filled PPS compound [325]. 

This chapter describes the use of AFM as a methodology for characterizing dendritic macromolecules and their self-assembled films. Systematic AFM studies of the PAMAM dendrimers properties (e.g. their size, shape, rigidity, packing textures and molecular weight calculations) will be fully addressed in this chapter. 

A study compared the buccal mucoadhesive properties for different polymeric films that differed in their cross-linking status [91]. Synthetic (Carbopol 971P, PCP), semisynthetic (SCMS), and natural carrageenan (X-type) were analyzed for their mucoadhesive properties using a TA-XT2i texture analyzer. 

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