Prediction of elastic parameters of photoluminescent porous Si

The discovery of photoluminescence properties of highly porous silicon, PS, has recently attracted considerable research. To enrich the understanding of this material, we carry out an investigation of its elastic properties which are of great importance in any opto-, nano-, micro-device applications. By considering 80%-and 70%-porosity PS layers, we deduced their SAW velocities (longitudinal, V_L, and transverse, V_T); they were found to be: (V_L)_80% = 1677 m/s, (V_L)_70% = 1868 m/s, (V_L)_80% = 1041 m/s, (V_T)_70% = 1160 m/s, (V_R)_80% = 969 m/s and (V_R)_70% = 1080 m/s. Then, their reflection coefficients and acoustic signatures were calculated, plotted and spectrally analyzed. Hence, the optimal conditions for eventual measurements of these parameters by a scanning acoustic microscope were determined (spherical acoustic lens of 50deg, freon as a coupling liquid and variable operating frequencies: 58 MHz, 142 MHz and 565 MHz).