Flux growth technique

Synthetic emeralds. Emeralds can be synthesized either by flux-growth or hydrothermal processes. The flux-growth techniques is used by Chatham Research Laboratories in San Francisco, United States and Les fitablissements Cdramiques Pierre Gilson, while the hydro-thermal synthesis once utilized by Union Carbide (1965-1970) is currently employed by Biron and Vacuum Ventures. Synthetic emeralds are easily distinguished from naturals by their lower indices of refraction and densities, and by their distinct inclusions. 

The development of a low temperature crystal growth technique utilizing KOH as a flux by Wignacourt et al. (10) and his demonstration of its utility for studying the composition - structure... 

A schematic phase diagram of MBE growth is depicted in fig. 4 (Ohno 1998 Shen et al. 1999). Recently it was shown that metallic (Ga,Mn)As with x = 0.1 can be obtained by the use of a modified MBE growth technique at 7s = 150°C, migration-enhanced epitaxy (MEE), where the beam fluxes of source materials are precisely controlled (Sadowski et al. 2001a, 2001b). 

Atomic layer epitaxy (electrochemical) — Electrochemical atomic layer epitaxy (ECALE) is a self-limiting process for the formation of structurally well-ordered thin film materials. It was introduced by Stickney and coworkers [i] for the layer by layer growth of compound semiconductors (CdTe, etc.). Thin layers of compound semiconductors can be formed by alternating - underpotential deposition steps of the individual elements. The total number of steps determines the final thickness of the layer. Compared to flux-limited techniques... 

Because of the small volume of liquid phase, the Verneuil process is predestined to the growth of graded materials. The development of the flux-Verneuil technique [4] enables the variation of the material support to the growing crystal. In this way, a specific influence on the stoichiometry of the liquid phase is possible. 

Hot Wall Epitaxy (HWE). HWE is a high vacuum variant of physical vapor deposition with a base pressure of 10 6 mbar [9], In contrast to many other growth techniques it utilizes the near field of the molecular beam by moving the sample close or even into the hot wall tube that holds the film material. The walls of the tube can be heated separately and are held on a higher temperature than the sample and the source. This prevents deposition on the tube wall and helps to create a uniform flux of molecules. The main advantages of HWE are that the films are grown close to the thermodynamic equilibrium. The main drawback is that the position of the sample close to the evaporator makes an in situ characterization of the film growth impossible. 

If the desired compound melts incongruently it is often easier just to use a technique like flux growth to obtain single crystals. 

Fig. 22. A brief classification of R123 crystal growth techniques on a basis of different phenomena taking place at various interfaces between solid, liquid and gaseous phases participating in the solidification process (a) possible interface boundaries and phenomena connected with the presence of such interfaces (b) different interfaces present in the self-flux method note that numbers in brackets correspond to the general scheme of classification (a) (c) a number of interfaces and phenomena of some importance for the unidirectional solidification method note that (crystal-high-temperature phase and melt-high-temperature phase) interfaces are close to each other (d) different interfaces and phenomena to be considered in the SRL-CP pulling technique of bulk crystal production note that solute transport and nudeation can be controlled in order to achieve a desired morphology of the crystal.

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