Memory effect in low-density amorphous silicon under pressure

Abstract

Our investigations on porous Si (π-Si) show that on increase of pressure it undergoes crystalline phase transitions instead of pressure-induced amorphization, as suggested earlier, and the amorphous phase appears only on release of pressure. This amorphous phase, when subjected to higher pressures, transforms reversibly to a higher-coordinated primitive hexagonal phase, showing a kind of memory effect which may be the only example of its kind in the elemental solids. First-principles calculations and thermodynamic arguments help understand these observations.