PRESSURE-INDUCED PHASE-TRANSITION IN POROUS SILICON

High pressure studies of porous silicon reveal that a phase transition occurs at approximately 170 kbar. The phase transition is detected by an abrupt change in color of porous silicon from orange-yellow to bla ck. Photoluminescence measurements show an initial blu shift of the lu minescence peak. At approximately 25 kbar the blue shift ceases and a reversal of shift is observed. The red shift continues up to approxima tely 90 kbar at which point the luminescence is quenched. The shift re versal is interpreted as a pressure-induced direct-indirect transition in porous silicon. The results are best explained in the context of t he quantum confinement model.