Texture-oriented films substrates

Oriented In-Plane Texture. In this kind of film the properties (H and in the various in-plane directions (texture and nontexture directions) are different. The texture of the film can be supported by the texture of the substrate and the crystal lattice can be smaller in the texture direction than in the transverse direction. This can be the source for strain-induced magnetic anisotropy (magnetostriction). It is also found that the crystal is aligned in the texture direction (92). 

Fig. 4.2 (Left) XRD patterns (CuK ) of equally thick ZnSe (ca. 1 xm) deposits prepared on H (a) and on CdSe/Ni (b), at a deposition potential of -0.7 V vs. SHE from a typical acidic (pH 3) solution. The reflection intensities for ZnSe(l 11) are denoted in the figure (right) XRD patterns within the low-angle region showing the (111) reflections of ZnSe/CdSe heterostructures (A). Overlayers of ZnSe were deposited on CdSe films of various (111) texture intensities. The substrate features are shown in (B) in full-intensity scale. Evidently, the preferential orientation of the ZnSe crystallites increases with that of the CdSe substrate, up to a constant limiting value. (Reprinted from [16], Copyright 2009, with permission from Elsevier)...

A SEM image of diamond particles is shown in Figure 9.15. Unlike past works, diamond film surfaces were well facetted with (111) and (100) faces, or consisted of cubo-octahedrons. Under certain conditions, either (111) or (100) faces of diamond particles were nearly parallel to the substrate surface. It is of intrigue that the (1 ll)-oriented diamond grains have hexagonal faces, as seen in Figure 9.15, rather than triangles that were seen in Refs. [186, 187]. Thus, both (111)- and (100)-textured diamond films were demonstrated to be synthesized on poly-crystalline Cu foils. 

In the UPS measurements we were able to prepare the (SN)x films inside of the LHV chamber. X-ray analysis and electron reflection patterns show the (102) plane of (SN)x to lie parallel to the substrate plane in a textured orientation. 

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 preferentially oriented films on YSZ substrates exhibit extremely sharp resistive transition with zero resistance obtained at temperatures of 90 K and above. Typical resistivity vs temperature results are shown in Fig. 6 for a 1 pm thick film. The 10-90% transition width is 1.5 K and zero resistance is obtained at 91.4 K. On some films we have observed zero resistance at temperature as high as 94 K, which is one of the highest values reported for films of 1-2-3. When the films are reacted for a longer period to convert all the BaFj, the transition gets broader, with zero resistance obtained at 80-85 K. The critical current density (J,) of films with T,(R=0) higher than 90 K is about 10 A/cm at 77 K and 10< A/cm at 4 K. Films with broader transitions, which are also less textured, have critical current densities an order of magnitude lower. 

The chapter begins with an overview of elastic anisotropy in crystalline materials. Anisotropy of elastic properties in materials with cubic symmetry, as well as other classes of material symmetry, are described first. Also included here are tabulated values of typical elastic properties for a variety of useful crystals. Examples of stress measurements in anisotropic thin films of different crystallographic orientation and texture by recourse to x-ray diffraction measurements are then considered. Next, the evolution of internal stress as a consequence of epitaxial mismatch in thin films and periodic multilayers is discussed. Attention is then directed to deformation of anisotropic film-substrate systems where connections among film stress, mismatch strain and substrate curvature are presented. A Stoney-type formula is derived for an anisotropic thin film on an isotropic substrate. Anisotropic curvature due to mismatch strain induced by a piezoelectric film on a substrate is also analyzed. 

Although deposition conditions for the preparation of YBa2Cu307-5 films are often optimized to produce c-axis-oriented films that exhibit high critical currents, polycrystalline films appear to be better suited for the fabrication of sensitive conductive polymer/superconductor structures. These superconductor thin films are more textured and have lower critical currents than the smooth films, which are prepared with what would normally be considered more optimized deposition conditions. The weak link characteristics of these thin films are also enhanced by depositing the superconductor onto cleaved MgO substrates. These substrates possess natural step edges and can be exploited to further disrupt the connection between selected superconductor grains. 

The rather weak response of 5T and 6T [174] is due to the unfavorable orientation of the long molecular axis with respect to the normal of the textured thin films. Since the long molecular axis makes an angle of 32° with respect to the normal [12,133] (section 7.4.3.1), the lowest Bu state contributes accidentally very little to the actual three-photon resonance enhancement (vide infra). A marked increase of the three-photon resonance would be observed if the long axis would lie in the substrate plane. 

Figure 9.5 GIXD used to study the crystalline information in thin films. (A) Randomly oriented (similar to powder) arrangements of crystallites, with no preference for a specific crystallographic orientation (100) with respect to the substrate normal, produces rings in the diffraction patterns. (B) Textured or oriented films with a distribution of crystallite orientations produce arcs of diffracted intensity. (C) Highly oriented films produce spots or ellipses. The corresponding 2D GDCD patterns for PBITT that are solid state pressed (A), as spun from solution (B) and annealed (C), are used as examples at bottom. The pressed sample (A) is mostly-not completely-randomly oriented. Reprinted from ref. 54 with permission from the American Chemical Society.

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