Microstructural characterization of unidirectionally frozenin situ Sn-Se eutectic composites

An array of lamellar SnSe-SnSe₂ structure is obtained by unidirectional solidification, in which SnSe and SnSe₂ are, respectively,p andn type semiconductors. Their structural morphology was examined with use of transmission and scanning electron microscopes. It was found that the ordering of the alternative layers of the phases could be accomplished by a suitable choice of freezing rates, although several kinds of structural defects such as terminations, misfit lamellae and colony structure were observed. The mechanisms of these defect formations were considered in terms of the constitutional supercooling. Furthermore, the crystallographic relationship between the two phases in the solidified state was determined.