Textured films

Grain size in textured films. For films having a preferred growth direction—e.g., (111)—LEED can be used to determine the preferred direction and the grain size parallel to the surfrce. The preferred direction is obtained from the symmetry of the diffraction patterns, while the grain size is obtained from the shape in angle of diffracted beams. 

Where Jo and S are the current density of the primary beam and the area of the irradiated sample, Z is the wave length, Ohki the structure factor amplitude, Q the volume cell, Z a factor that takes the microstructure of sample into account (Zm - for a mosaic single crystalline film, Zt - for a texture film), t is the sample thickness, dhu the interplanar spacing, a represents the mean angular distribution of the microcrystallites in the film, p is a multiplicity factor (accounts for the number of reflections of coincidence), R is a horizontal coordinate of a particular reflection in DP from textures and (p is the tilt angle of the sample. In the case of polycrystalline films, a local intensity is usually measured and the corresponding relation is ... 

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. 

Since the preparation of RNi2B2C thin films is now well established, it will be used in future work to prepare single-phase films and even textured films of systems that are difficult to produce as bulk materials, e.g., the metastable phase YPd2B2C (see Section 2.4) or M2B2C mixed systems (see Section 6). 

Fig. 7.9. RHEED images of optimized ZnO thin film surfaces on r-plane, a-plane, and c-plane sapphire, in the two azimuthal orientations (top and bottom) separated by 45° (left) or 30° (middle and right), respectively. The RHEED patterns of the a-axis textured film on r-plane sapphire (left) indicate an epitaxial and three-dimensional, island-like growth. The ZnO films on a-plane (middle) and c-plane sapphire (right) exhibit a smoother surface structure, as indicated by the streaky RHEED patterns and the observation of additional weak reflections in the top images due to 3 x 3 surface reconstruction [51]...

More recently there has been some interest in producing molybdenum disulphide by electrochemical deposition. Much of this work has been aimed at producing large crystals for use as semi-conductors, but Ponomarev et al reported the production of highly-textured films with basal plane orientation by cathodic electrochemical deposition from tetrathiomolybdate solutions, followed by annealing at 550°C in argon. 

It is well known that nitrogen can be easily incorporated in diamond, and usually, it must be very eareful of the air leak in the CVD chamber to prevent nitrogen contamination of diamond films. It is also known that addition of too much nitrogen to the source gas resulted in microcrystalline diamond films rather than well-faceted films. However, Koidl s group found [90] using a NIRIM-type reactor that an addition of small amount of N2 gas to the source gas of c=l-2%CH4/H2 resulted in pronounced (100)-textured films, while the film became microcrystalline without N2 addition. More specifically, an addition of 40-200 ppm of N2 to the... 

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. 

In the case of the homoepitaxial or heteroepitaxially textured films of 100 orientation, the microstructure and morphology of the films are... 

The microstructure (texture, orientation) and morphology of diamond films can be controlled by varying the growth parameter a (a=(vioq/vj j j) ), which depends primarily on gas composition and substrate temperature. For fiber-textured films, at low CH4 concentrations and increasing substrate temperatures (a < 1.5), the films exhibit pronounced <110> texture at medium CH4 concentrations and substrate temperatures (1.5 < a < 3), a transition of the fiber axis from <110> to <100> occurs a further increase in CH4 concentrations or decrease in substrate temperatures (a > 3) leads to fine-grained, non-faceted films. 

The concentration of molecular nitrogen in the source gas was recognized as a very important third parameter determining the growth morphology and texture Small amounts (lO-lOOp.p.m.) of nitrogen were found to improve the crystalline perfection and favor the formation of smooth 001 [-faceted (001 [-textured films considerably [22]. An analysis of HF-CVD homoepitaxial film growth rates... 

Chem. Descrip. Food starch modified derived from waxy maize Uses Texturizer, film-former, gum Arabic replacement in pan coating of confections and tablets, as glaze for bakery items, as egg wash replacement on baked goods, as coating for adhesion of seasonings and seeds to crackers and nut meats... 

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