An Experimental Study of the Growth of Zinc Crystals by the Czochralski-Gomperz Method

Abstract

The conditions necessary to grow zinc single crystals of 2.7 mm diameter and of any desired orientation are determined experimentally. When a constant rate of growth is used and the crystal is initially given the desired orientation by starting it on a suitable nucleus the determining factor for the successful growth of a single crystal rod 10 cm or more in length is found to be the temperature gradient existing in the column of liquid zinc just below the growing crystal. The appropriate temperature gradient is a function of the orientation of the crystal. It is depicted graphically in a figure which shows the upper and lower limiting curves for the region of successful growth when the rate of growth is 1.2 cm/min. The lower curve rises from orientation 0 to 45° and falls from 45 to 90°. The upper curve lies slightly above and parallel to the lower curve from 0 to 50°, but then rises very sharply. The shape of this region does not seem such as to be attributed only to variation in heat conductivity with orientation. Attempts to grow crystals outside of the appropriate region result in sudden or gradual changes to new orientations. In the latter the orientation shifts gradually through a considerable range. Illustrations are given of such changes.