INTERNAL RADIATIVE HEAT-TRANSFER IN CZOCHRALSKI GROWTH OF LITAO3 SINGLE-CRYSTAL

In order to investigate the effect of internal radiative heat transfer on growth behavior in the oxide Czochralski single crystal growth pro cess, differently colored LiTaO3 single crystals were grown in N2 + 0. 5 vol% O2 and N2 atmospheres. In the N2 + O2 atmosphere, transparent y ellow crystals of 55 mm in diameter and 70 mm in length could easily b e grown. The crystals have convex interfaces toward the melt. On the o ther hand, the crystals grown in the N2 atmosphere are brown because o f O2 deficiency. The brown crystals have concave interfaces and it was difficult to grow long crystals by using the hot zone with the same s tructure as that used in the N2 + O2 atmosphere. From measurements of temperature gradient in the growth furnace, temperature changes around crystals in the crucible with O2 introduction into the N2 atmosphere and emitted spectra from growing crystals in the N2 and N2 + O2 atmosp heres, it is concluded that increase of the resistance to heat transfe r due to the suppression of the internal radiative heat transfer in th e colored crystals is responsible for the growth difficulties such as concave interfaces.