POROUS SILICON OF VARIABLE POROSITY UNDER HIGH HYDROSTATIC-PRESSURE -RAMAN AND PHOTOLUMINESCENCE STUDIES

Raman scattering and photoluminescence measurements have been performe d in free standing porous silicon, for the first time at hydrostatic p ressures up to 21 GPa. The pressure dependence of the porous silicon p hotoluminescence and Raman scattering has been systematically investig ated as a function of porosity. Spectral features of both the Raman an d PL bands exhibit almost the same transition pressures and depend on the maximum pressure achieved. Highly porous silicon (>80%) transforms at 18 GPa resulting in unrecoverable suppression of Raman and lumines cence activity.