XAFS INVESTIGATIONS OF FERROELECTRIC-IV-VI SEMICONDUCTORS

Using X-ray Absorption Fine-structure Spectroscopy, we have investigated the local structure of the Pb1-xGexTe and PbTe1-XSx alloy systems. In all cases, we find the smaller substitutional ion off-center from the cell center, and these off-center ions appear to undergo an orientational order-disorder transition. Using XAFS, we are also able to clearly map the relative shift between the cation and anion sublattices below the Curie temperature, showing that the transitions in these materials exhibit both order-disorder and displacive character. Here, we review previous work on Pb1-xGexTe and present new results on PbTe1-xSX, thereby showing the effect in materials with both cation-sublattice and anion-sublattice disorder. © 1991, Taylor & Francis Group, LLC. All rights reserved.