HIGH-PRESSURE SRX-RAY DIFFRACTION STUDIES OF STRUCTURAL AND ELASTIC ASPECTS OF SUPERLATTICES

This paper reports on the development of our new high-pressure X-ray d iffraction technique to study elastic and structural aspects of superl attices simultaneously. By applying hydrostatic pressure to a superlat tice specimen in a diamond-anvil cell, synchrotron radiation X-rays pr obe its elastic response and structural change resulting in the peak s hift and intensity of Bragg reflections. Two metallic superlattices, A u/Ni and Mo/Ni, have been found anomalously incompressible (supermodul us) along the perpendicular (layer stacking) direction, while a semico nducting superlattice, PbSe/SnSe, shows no anomaly in its elasticity b ut undergoes a cubic-to-orthorhombic phase transition layer-by-layer s ystematically depending on the thickness.