| Research Abstract |
Amorphization from the quenched high-pressure phase with the beta-Sn structure has been studied for several semiconductors. Results were analyzed by using a configuration-coordinate model. The temperature dependence of the intensity of the diffraction peaks gives information concerning the potential barrier *U between the two phases of the before- and after-phase transitions.
X-ray diffraction measurements at high pressures and low temperatures were carried out by an energy dispersive method using a synchrotron radiation.
When pressure is released at 90 K, the high pressure phase of GaSb is quenched. The quenched high pressure phase shows amorphization when temperature is increased below 1 GPa, while it transforms to ZnS phase above 1 GPa. Similar amorphization occurs when temperature is decreased below 270 K.With increasing pressure at 300 K, AlSb transforms into the beta-Sn phase at 8-10 GPa. With decreasing pressure, the high pressure phase returns to the ZnS phase at 4-2 GPa. On the other hand, the high pressure phase of AlSb is quenched at 100 K when pressure is released. The quenched high pressure phase shows amorphization when temperature is increased at 2.5 GPa and 2.0 GPa. When temperature is elevated at 3.5 GPa, however, the quenched high pressure phase returns to the ZnS phase from 280 K to 340 K.Similar amorphization was also observed when pressure was reduced at 240 K and 270 K, while the phase transition to the ZnS phase was observed at 300 K and 330 K.
Analysis from a configurational coordinate model proves that the pressure derivative of *U to the amorphous phase is much larger than that to the ZnS phase. Reverse of inequality occurs at 3 GPa.
For InAs and CdTe with much larger ionicity, only the transition to the ZnS phase was observed. A large ionicity in the bonding nature should lower *U to the ZnS phase. Thus the phase transition to the ZnS phase occurs at higher pressure where *U to the ZnS phase is lower than *U to the amorphous phase.
|
