Czochralski method

Lithium Niobate. Lithium niobate [12031 -64-9], LiNbO, is normally formed by reaction of lithium hydroxide and niobium oxide. The salt has important uses in switches for optical fiber communication systems and is the material of choice in many electrooptic appHcations including waveguide modulators and sound acoustic wave devices. Crystals of lithium niobate ate usually grown by the Czochralski method foUowed by infiltration of wafers by metal vapor to adjust the index of refraction. 

TJItrahigh (99.999 + %) purity tellurium is prepared by zone refining in a hydrogen or inert-gas atmosphere. Single crystals of tellurium, tellurium alloys, and metal teUurides are grown by the Bridgman and Czochralski methods (see Semiconductors). 

The Czochralski Method has remained the most frequently employed method for obtaining single crystals. The seemingly formidable complexities involved have been conquered by the use of computer-control of the crystal-growing Parameters. One such system, available commercially, is shown in 6.4.12. (on the next page). 

A final comment on the Czochralski Method GaAs has become important in construction of integrated circuits for computers because of the promise of speed of response and density of components, compared to silicon wafers. Both As and Ga tend to oxidize in air as they approach the melt stage and AS2O3 sublimes. Both elements are toxic to man. In the... 

T. Inada and T. Fukuda, Direct Synthesis and Growth of Indium Phosphide by the Liquid Phosphorous Encapsulated Czochralski Method O. Oda, K. Katagiri, K. Shinohara, S. Katsura, Y. Takahashi, K. Kainosho, K. Kohiro, and R. Hirano, InP Crystal Growth, Substrate Preparation and Evaluation K. Tada, M. Tatsumi, M. Morioka, T. Araki, and T. Kawase, InP Substrates Production and Quality Control... 

The so-called liquid-encapsulated Czochralski process, a modified version of the Czochralski method, is extensively used for preparing and growing III-V crystals. 

Fig. 10. Pulling of a single crystal of UNi from the levitated melt by the Czochralski method...

Figure 2.1. Various forms exhibited by crystals, (a) Polyhedral crystals (b) hopper crystal (c) dendritic crystal (snow crystal, photographed by the late T. Kobayashi) (d) step pattern observed on a hematite crystal (0001) face (e) internal texture of a single crystal (diamond-cut stone, X-ray topograph taken by T.Yasuda) (f) synthetic single crystal boule. Si grown by the Czochralski method (g) synthetic corundum grown by the Verneuil method.

The most common methods of growing crystals involve solidification from the melt (in the case of one-component systems) or crystallization from solution. Some of the methods for growing crystals from melt are described schematically in Fig. 3.6. In the Czochralski method, commonly known as the pulling technique, the material is melted by induction or resistance heating in a suitable nonreactive crucible. The melt temperature is adjusted to slightly above the melting point and a seed crystal is dipped into the melt. After thermal equilibration is attained, the seed is slowly lifted from the... 

Figure 3.6 Methods for crystal growth from melt (a) Czochralski method (b) Kyropoulos method (c) Bridgman-Stockbarger method and (d) Vemeuil method.

Fig. 3.52 Dependence of Hall mobility on the melt composition for GaAs crystals grown by the Czochralski method.

Large crystals of Rb2[CrCl4] and [N(CH2Ph)H3]2[CrCl4] have been grown the former from the melt by the Bridgman and Czochralski methods, and the latter by careful temperature control from solutions in sealed tubes.252,261... 

Czochralski method - [LITHIUM AND LITHIUM COMPOUNDS] (Vol 15) -for ceramic crystal [CERAMICS - NONLINEAROPTICAL AND ELECTROOPTIC CERAMICS] (Vol 5) -for LED substrates [LIGHT GENERATION - LIGHT-EMITTING DIODES] (Vol 15) -for photoconductors [PHOTODETECTOFE] (Vol 18)... 

Large crystals of both LiNb03 and LiTa03 can be grown by the Czochralski method (see Fig. 3.11). Their principal properties are given in Table 6.5 below. 

Lithium tantalate is a single-crystal material that is produced in quantity by the Czochralski method (see Section 3.11) for piezoelectric applications and is therefore readily available. It is stable in a hard vacuum to temperatures that allow outgassing procedures. It is insensitive to humidity. It is widely used where precise measurements are to be made. 

Strontium barium niobate is a single-crystal material with the tungsten bronze type of structure which is made by the Czochralski method but has yet to find a major use. It has relaxor characteristics of the type shown in Fig. 7.1 which give it a high pyroelectric coefficient and detectivity, but its high permittivity lowers the figure of merit l. ... 

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