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A transparent computer controlled muti-zone furnace was
developed for vertical dynamic gradient freeze(VDGF) growth of
Benzil single crystals for nonlinearoptics. The effects of
impurities, heating profiles and speeds on the growth rates, the
interface shape, and constitutional supercooling were
investigated through close-up observation andcomputer
simulation. In addition to good agreement between experiments
andsimulation, it was found that the constitutional
supercooling, rather thanthe interface shape, was the key factor
for a successfulgrowth. In other words, raw material
purification and ahigher temperature gradient (G) / growth
rate(R) ratio for growth for preventing supercooling
werecrucial. Benzil single crystals with good optical
transparency were grown, and their absorption spectrum in the
visible-light range was notaffected by growth conditions and
post-annealing.
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