Te solvent zone in THM

Choice of the dimensions of the Te zone and control of its interface shape are considered essential in determining the crystallinity. For example, for the growth of rods 10 mm in diameter and ~60 mm long, Schoenholtz demonstrate that a 3 mm wide Te zone generates polycrystalline boules, the grain size being 0.5 of the diameter of the rod. Using of a 4 or 6 mm wide zone generated sing crystals rods,albeit with twins. Multiple passes of Te zones were not found to eliminate grains and twins.
Funaki et al extended the diameter of THM CdTe to 50 mm and found that a Te zone in the range 30-50 mm was most effective, with the very best results being obtained for a 40 mm zone. It was noted that for zones of greater or smaller width, the convex interface shape included inflection points which likely to introduce grain boundaries.

The ideal solvent zone height (h) and ampoule diameter (x) have following relations;
h = 0.471134 x + 5.16234E-3 *x^2.
For example, 12.8 mm solvent height is optiaml for 22 mm diameter of CZT ingot growth.