Fiber-textured films

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 film is fibrillated mechanically by mbbing or bmshing. Immiscible polymers, such as polyethylene or polystyrene (PS), may be added to polypropylene to promote fibrillation. Many common fiber-texturing techniques such as stuffer-box, false-twist, or knife-edge treatments improve the textile characteristics of slit-film fibers. 

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. 

As we have seen, the orientation of crystallites in a thin film can vary from epitaxial (or single crystalline), to complete fiber texture, to preferred orientation (incomplete fiber texture), to randomly distributed (or powder). The degree of orientation not only influences the thin-film properties but also has important consequences on the method of measurement and on the difficulty of identifying the phases present in films having multiple phases. 

R. W. Smith. A kinetic Monte Carlo simulation of fiber texture formation during thin-film deposition. J Appl Physics 57 1196, 1997. 

The required degree of understanding of the physical properties of metal thin films used for interconnects on chips is illustrated by the following example. It was found that the performance of conductors on chips, A1 or Cu, depends on the structure of the conductor metal. For example, Vaidya and Sinha (10) reported that the measured median time to failure (MTF) of Al-0.5% Cu thin films is a function of three microstructural variables (attributes) median grain size, statistical variance (cr ) of the grain size distribution, and degree of [111] fiber texture in the film. 

The diagrams thus show, on the scale of the anisotropic areas, a fiber texture similar to that described by Kuroda (2, 13) for petroleum cokes and Kakinoki (12) for thin films of carbon. The presence of the arcs 002, when the electron beam is not perpendicular to the C-axis, is caused by the fact that the texture axis shows some dispersion. This, however, does not prevent each area from having an average direction of the axis 002 different from that of the adjacent ones. 

The wire is examined in a transmission pinhole camera with filtered radiation and with the wire axis vertical, parallel to one edge of the flat film. The problem of finding the indices uv v of the fiber axis is best approached by considering the diffraction effects associated with an ideal case, for example, that of a wire of a cubic material having a perfect [100] fiber texture. Suppose we consider only the 111 reflection. In Fig. 9-9, the wire specimen is at C with its axis along NS, normal to the incident beam IC. CP is the normal to a set of (111) planes. Diffraction from these planes can occur only when they are inclined to the incident beam at an angle 6 which satisfies the Bragg law, and this requires that the (111) pole lie somewhere... 

A transmission pinhole pattern is made with Co Ka radiation of an iron wire having an almost perfect [110] fiber texture. The wire axis is vertical. How many high-intensity maxima will appear on the lowest-angle 110 Debye ring and what are their azimuthal angles on the film ... 

An electroplated layer of copper on sheet steel is examined in a back-reflection pinhole camera with Cu Ka radiation incident at right angles to the sheet surface. Assume the copper has a fiber texture with the fiber axis [ww] scattered by an angle p in every direction about the sheet normal. How large must p be for the 420 Debye ring (see Table 4-2) to appear on the film if the fiber axis [//yw] is (a) [110], (b) [100] ... 

Abstract. Structural properties of rubrene thin films on cleaved mica (001) surfaces were investigated by optical microscopy and x-ray diffraction. Optical microscopy shows, that the crystallization of rubrene results in formation of spherulites. X-ray specular diffraction reveals polycrystalline and polymorphic nature of rubrene. The pole figure measurements of films prepared at low deposition rates reveal orthorhombic structure and indicate fiber textures with crystallographic planes (121), (131) and (141) preferentially oriented parallel to the substrate surface. High deposition rate thin films in addition show polymorphism, corroborating the existence of the orthorhombic and the triclinic phase. 

The degree of the (110) fiber texture improves (i.e., a preferential orientation of 110 planes develops) with increasing film thickness. However, the film texture and surface morphology are critically dependent on the growth conditions. Under conditions where 100 or both 100 and 111 planes develop, the preferred orientations different from the (110) fiber texture may form. 

Diamond homoepitaxy and heteroepitaxy have been achieved on diamond and cBN, respectively. Epitaxially textured and fiber textured, highly oriented diamond films have been grown on Si(lOO). The feasibility of diamond heteroepitaxy on Ni, Ti, Co and Cu has also been confirmed by several experiments. Diamond can grow on Fe, but not yet by epitaxy. 

According to the principle of evolutionary selection, the development of fiber textures is a result of the growth competition between randomly oriented diamond crystals, and the resultant direction of fiber axis coincides with the direction of fastest growth. With increasing film thickness, bofii crystal size and size spectrum increase, and the degree of texture improves with concomitant reduction of overall misorientation. 

Two methods will be presented here allowing the preparation of films in which the crystallites have lost two and three degrees of freedom. By an appropriate control of the growth process, diamond films with fiber texture can be fabricated, in which... 

Figures 4, 5 and 6 show examples of normalized experimental pole figures. For Fig. 4 the material is a TiN fine-grained polycrystalline thin film. Such thin films, which are produced by a physical vapor deposition (PVD) method, are used in microelectronics as diffusion barriers between the silicon from one side and the aluminum current lines on the other side. From the (111) and (200) pole figures one can easily recognize that nearly all the crystallites have a (111) crystal direction parallel to C, the normal to the specimen, and are uniformly arranged around this direction. This corresponds to a so-called fiber texture.

Basceri, C., Streiffer, S.K., Kingon, A.I., Waser, R. The dielectric response as a function of temperature and film thickness of fiber-textured (BaSr)Ti03 thin films grown by chemical vapor deposition. J. Appl. Phys. 82(5), 2497-2504 (1997)... 

Oba, F., Ohta, H., Sato, Y, Hosono, H., Yamamoto, T, and Ikuhara, Y (2004) Atomic structure of [OOOlj-tilt grain boundaries in ZnO A high-resolution TEM study of fiber- textured thin films. Phys. Rev. B, 70, 125415-125420. 

Supported bis(imino)pyridyl metal catalysts on SiO2/Si(100) wafers were used for ethylene polymerization in solvent. Since the catalysts are covalently anchored to the flat surface, polymers can only grow perpendicularly to the flat surface and form films of almost constant height. As the polymerization reaction occured weU below the dissolution temperature of polyethylene, all polymer remained on the catalyst surface [27]. A typical morphology is shown in the SEM images in Fig. 1 for a PE film polymerized from the SiO2/Si(100) wafer-supported bis(imino)pyridyl iron(II) catalyst in a toluene solution. Islands of polymer are observed on the top of the PE films. Between these islands, a fiber texture is found. This morphology is more apparent from the side view. 

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