Czochralski parameters

The next most importtmt parameters in Czochralski growth of crystals are the heat flow and heat losses in the system. Actually, aU of the parameters (with the possible exception of 2 and 9) are strongly ciffected by the heat flow within the crystal-pulling system. A tj pical heat-flow pattern in a Czochralski sjretem involves both the crucible and the melt. The pattern of heat-flow is important but we will not expemd upon this topic here. Let it suffice to point out that heat-flow is set up in the melt by the direction of rotation of the cr5rstal being pulled. It is also ctffected by the upper surface of the melt and how well it is thermally insulated from its surroundings. The circular heat flow pattern causes the surface to radiate heat. The crystal also absorbs heat and re-radiates it... 

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). 

The parameters which control CZOCHRALSKI GROA H are listed in the order of their importance in 4.2.7., given on the next page. All of these... 

Returning to Czochralski crystal growth, of the 9 parameters given in... 

The next most important parameters in Czochralski growth of crystals are the heat flow and heat losses in the system. Actually, all of the parameters (with the possible exception of 2 and 9) are strongly affected by the heat flow within the crystal-pulling stem. The next section addresses this factor. 

Mateika, D., Laurien, R. Rusche, Ch. (1982). Lattice parameters and distribution coefficients as function of Ca, Mg and Zr concentrations in Czochralski grown rare earth gallium garnets. Journal of Crystal Growth, 56, 677-89. 

The calculations were carried out in the framework of the model of point defect dynamics, i.e., for the same crystals with the same parameters as in already the classical work on the simulation of microvoids and interstitial dislocation loops (A-microdefects) (Kulkarni et al., 2004). According to the analysis of the modern temperature fields used when growing crystals by the Czochralski method, the temperature gradient was taken to be G = 2.5 K/ mm (Kulkarni et al., 2004). The simulation was performed for crystals 150 mm in diameter, which were grown at the rates Vg = 0.6 and 0.7 mm/ min. These growth conditions correspond to the growth parameter Vg/ G >... 

In practice, crystal growing experience based on experimentation counts for much in choosing suitable growth parameters for the wide variety of physical properties to be encountered in rare earth metals and compounds. There are three main versions of the Czochralski technique currently used throughout the rare earth crystal growing community. One employs a hot crucible, the other two use cold crucible containment. 

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