Substrate amorphous

In Sect. 3.7.1, we present one example which shows how texture may determine the physical properties and reliability of thin films. 

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The oriented overgrowth of a crystalline phase on the surface of a substrate that is also crystalline is called epitaxial growth [104]. Usually it is required that the lattices of the two crystalline phases match, and it can be a rather complicated process [105]. Some new applications enlist amorphous substrates or grow new phases on a surface with a rather poor lattice match. 

Transmission electron microscopy (tern) is used to analyze the stmcture of crystals, such as distinguishing between amorphous siUcon dioxide and crystalline quartz. The technique is based on the phenomenon that crystalline materials are ordered arrays that scatter waves coherently. A crystalline material diffracts a beam in such a way that discrete spots can be detected on a photographic plate, whereas an amorphous substrate produces diffuse rings. Tern is also used in an imaging mode to produce images of substrate grain stmctures. Tern requires samples that are very thin (10—50 nm) sections, and is a destmctive as well as time-consuming method of analysis. 

The metal size clearly increases when the decomposition takes place on the substrate. Nevertheless, the overall shift after complete decomposition is the same both on crystalline and amorphous substrates. This can be explained by the assumption that the increase of the number of the metal atoms in the cluster takes place also on an amorphous substrate, on a scale high enough to shift the core levels but low enough to maintain a constant emitted intensity ratio between the substrate and the metal core levels. The authors concluded therefore that the core-level position is highly size-sensitive in the range of very small particles, e.g. < 100 atoms where the associated electronic properties are primarily atomic. However, on approaching the metallic state for >100 atoms, the corelevel shift is a much poorer criterion of the cluster size. 

Polycrystalline films deposited on amorphous substrates are of lower crystallographic surface heterogeneity the higher the temperature of annealing subsequent to deposition or the higher the substrate temperature during deposition again, photoelectric work-function data serve to emphasize the point (9,10, 12,18). 

Fig. 16 Molecular trajectory in the early stage of chain adsorption onto the thin substrate. The chain atoms on the crystalline substrate and the amorphous substrate are depicted in dark gray and in white, respectively. The presence of longloops in the amorphous region is quite pronounced...

Here we examine models that try to explain how textures develop during deposition on oriented (single-crystal), textured, polycrystalline, and amorphous substrates. We select electrodeposition of nickel as a model system. 

When Lsub is kept constant and Dt is varied, similar selectivity in the film orientation is observed. Thin CuPc films prepared on amorphous substrates using PVD at Tsab = RT and low Dt (0.1 nm s ) are oriented with their (100) crystallographic planes preferentially parallel to the substrate surface (standing). At higher D (10 nm s ), an additional second type of preferred orientation is observed with (110) planes oriented preferentially parallel to the substrate surface (lying) (Resel et al, 2000). 

The metallorganic compounds (I, II) employed in presence of a heterogeneous phase containing an amorphous compound of a low-valency, strongly electropositive transition metal, generally polymerize a-olefins to amorphous polymers. In a similar fashion, the soluble reaction products of such metallorganic compounds with compounds of transition metals, chemisorbed on amorphous substrates, polymerize a-olefins to amorphous polymers 6, 9). 

The reactants used for mordenite synthesis were an amorphous substrate of near-mordenite composition (Zeolex S-6-10, 0.91 Na -AkOa-10.6 Si02-7.4 H20, J. M. Huber Co.) and two different types of sodium sili-... 

Crystallization was followed by analyzing the solid product quantitatively by x-ray powder diffraction. Prepared mixtures of a standard sample of mordenite and the amorphous substrate of mordenite composition were used to establish a calibration curve for the quantity of mordenite based on the summation of x-ray peak intensities. For zeolites A and X, the unreacted aluminosilicate gel was used to prepare mixtures with standard samples of zeolites A and X for quantitative phase identification. 

E.I. Givargizov [ Oriented Crystallization on Amorphous Substrates (Plenum Press, New York, 1991) p.221-64 and references therein ]... 

Choi, J. H., Tabata, H., and Kawai, T. (2001). Initial preferred growth in zinc oxide thin films on Si and amorphous substrates by a pulsed laser deposition. J. Cryst. Growth 226 493-500. 

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