The effect of a transverse magnetic field on the microstructure of directionally solidified CdTe

Abstract

The purpose of this study was to examine several microstructural features in Bridgman-grown CdTe and determine whether the use of a tranverse, 4.6 kG magnetic field during solidification had any effect on these features. Any variation in these microstructural features due to the use of the magnetic field could be attributed to changes in the connective state of the melt and the resulting disruption or stabilization of the solid-liquid interface. In order to accomplish this objective, samples of CdTe were directionally solidified by the vertical Bridgman-Stockbarger method and a static magnetic field of 4.6 kG was applied transverse to the growth direction during the solidification of selected samples. The microstructural features examined included the preferred crystallographic growth direction of primary gains, grain and twin boundary length per unit area and etch-pit and subgrain boundary densities on a (111)-type plane. Measurements of these features were performed using the Laue X-ray backreflection technique and quantitative optical microscopy. No measurable difference in the microstructural features occurred as a result of using the 4.6 kG transverse magnetic field. The lack of any effect is attributed to either an insufficient magnetic field intensity or the possibility that the effect of a 4.6 kG transverse magnetic field on the fluid flow may not play a significant role in the mechanisms generating the microstructural features analyzed by the characterization techniques used in this study. Subgrain boundary densities were found to vary along the length of each boule and this variation was attributed to post-growth annealing.