Films amorphous “structure

The amorphous structure favours internal oxidation unless a protective oxide film is formed as, for example, under low oxygen partial pressures . 

The work on carbon nitride solids is strongly related to research on diamondlike carbon (DLC) materials [5, 6]. DLC materials are thin film amorphous metastable carbon-based solids, pure or alloyed with hydrogen, which have properties similar to that of crystalline diamond (high hardness, low friction coefficient, high resistance to wear and chemical attack). This resemblance to diamond is due to the DLC structure, which is characterized by a high fraction of highly cross-linked sp -hybridized carbon atoms. To obtain this diamond-like structure... 

The structure of a vapor-quenched alloy may be either crystalline, in which the periodicity of the unit cell is repeated within the crystallites, or amorphous, in which there is no translational periodicity even over a distance of several lattice spacings. Mader (64) has given the following criteria for the formation of an amorphous structure the equilibrium diagram must show limited terminal solubilities of the two components, and a size difference of greater than 10% should exist between the component atoms. A ball model simulation experiment has been used to illustrate the effects of size difference and rate of deposition on the structure of quench-cooled alloy films (68). Concentrated alloys of Cu-Ag (35-65%... 

Monodisperse analogs of such ir-electron systems, PPV oligomers (molecular glasses) were studied by Bazan and coworkers [217]. The films prepared from 192 by solution casting showed completely amorphous structure due to a tetrahedral structure of the molecule and OLEDs ITO/PVK/192/Al-emitted green light with an efficiency up to 0.22 cd/A (Chart 2.42). 

Although there is no consistent explanation of the relationship between organic polymer morphology and electrical properties,amorphous structures are generally preferred over a crystalline structure. An experiment was conducted to study the structure of the film deposited using an inert carrier gas. The PNT-N... 

Ion implantation (qv) has a large (1014 K/s) effective quench rate (64). This surface treatment technique allows a wide variety of atomic species to be introduced into the surface. Sputtering and evaporation methods are other very slow approaches to making amorphous films, atom by atom. The processes involve deposition of a vapor onto a cold substrate. The buildup rate (20 tm/h) is also sensitive to deposition conditions, including the presence of impurity atoms which can facilitate the formation of an amorphous structure. An approach used for metal—metalloid amorphous alloys is chemical deposition and electro deposition. 

Many other organic materials have been deposited by evaporation in vacuo but usually form either a polycrystalline or an amorphous structure. However, Hoshi et al. [424] have made some progress in depositing epitaxial films of lutetium diphthalocyanine on to single crystals of potassium bromide. Here again the temperature of the substrate is critical but only relatively small areas of continuous crystal have been obtained. 

The amorphous phase appearing above 20 GPa at room temperature (see above) has also recently been studied by X-ray diffraction [135] and Raman scattering [132,133]. Serebryanaya et al. [135] identify the structure as a three-dimensionally polymerized Immm orthorhombic lattice, but find that compression above 40 GPa gives a truly amorphous structure. In contrast to the orthorhombic three-dimensional polymer structure discussed in the last section, the best fit here is found for (2+2) cycloaddition in two directions, with (3+3) cycloaddition in the third, and thus some relationship to the tetragonal phase. From the in situ X-ray data a bulk modulus of 530 GPa is deduced, about 20% higher than for diamond. Talyzin et al. [132, 133] find that this phase depolymerizes on decompression into linear polymer chains, unless the sample is heated to above 575 K under pressure. A strong interaction with the diamond substrate is also noted, such that only films with a thickness of several hundred nm are able to polymerize fully [ 132]. Hardness tests were also carried out on the polymerized films, which were found to be almost as hard as diamond and to show an extreme superelastic response with a 90% elastic recovery after indentation [133]. 

Hydrocarbon gases, without any catalyst DLC Thin film, sp3 bond, amorphous structure... 

The electrochemical properties of passive layers lead to the question of their structure on a mesoscopic scale and at atomic resolution. Their barrier character with respect to metal corrosion postulates a dense, poreless film their electronic properties, in some cases, crystalline structures. The change of their properties with film aging, as in e.g. film-breakdown phenomena, support the existence of many defects that may heal with time. In many cases an amorphous structure is assumed. Some ex situ... 

In the case of passive layers the outer hydroxide film is always present. It is hydrated to a large extent, and thus does not correspond to crystalline Ni(OH)2. The incorporation of water leads to an amorphous structure of the outer part of the passive layer with the observed characteristic dense package of small grains. All these detailed investigations lead to the structure of the passive layer on Ni with a an inner crystalline oxide with a antiparallel orientation of its (111) planes relative to the (11 l)-oriented Ni surface with a tilt of 3° and an outer amorphous hydroxide part. 

Fig. 4.20. Evolution of the CdS and ZnO valence band maxima as derived from the binding energies of the core levels by subtracting BEvb(CL) values determined from the CdS substrate and the thick ZnO film, respectively [71], The different evolution of the Zn 3d and O Is binding energies is attributed to an amorphous structure of the ZnO layer during the initial growth. The thickness of the amorphous layer is 2 nm. The ZnO films were deposited by magnetron sputtering from an undoped ZnO target at room temperature using 5 W dc power...

Fig. 18.19 Top views of SEM images of nanotube layers Amorphous structures of N-ion implanted Ti02 nanotubes at 1 x 1015 ions per cm2 (a) and 1 x 1016 ions per cm2 (b) annealed anatase TiOj nanotube films before ion implantation at 1 x 1015 ions per cm2 (c) and 1 x 1016 ions per cm2 (d) [reprinted from Ghicov et al. (2006), copyright 2006, with permission from Elsevier]...

Figure 20 shows excellent step,coverage of one of the MOCVD BST films deposited by the dome type reactor with single injection nozzle at a wafer temperature of 413°C. The substrate has a linelspace pattern with an aspect ratio of 1 6 made of SiO covered with a very thin Pt film. The step coverage is more than 80%. The featureless surface morphology of the film implies that the film has an amorphous structure which should be crystallized by proper postannealing. As discussed previously, however, the hydrocarbon incorporation problem for low temperature CVD must be considered. 

The interface structure between a HOD film, made by the two-step process, and Si was observed by TEM in Ref. [313]. (fll)XPF measurements indicated that the FWHM was about 9°. In consistent with the results of Tzou et al. [314] there were two areas at the interface (i) an interfacial region with amorphous structure where the orientations of diamond grains were random, and (ii) an interfacial region... 

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