RAMAN-SCATTERING FROM FREE STANDING POROUS SILICON UNDER HYDROSTATIC-PRESSURE

Luminescence and Raman scattering experiments have been performed on d ifferent types of porous silicon (PS) samples as a function of the hyd rostatic pressure. These measurements allow to compare the response of the material in different structural phases and show that under moder ate conditions of pressurization the strong PS luminescence is still o bserved though the sample has been transformed in a structural phase d ifferent from the diamond phase. They provide also upper bounds on the degree of the phase transformation which is discussed. In addition sp ecific PS Raman features are observed for the first time on these tran sformed samples. It is concluded that the PS luminescence is not relat ed to the diamond phase of silicon and that the emitting medium involv es more likely surface related complexes of the material.