Electronic and Vibrational Properties of Porous Silicon

Abstract

For ordered porous silicon, the Born potential and phonon Green’s functions are used to investigate its Raman response, while the electronic band structure and dielectric function are studied by means of a sp3s* tight-binding supercell model, in which periodical pores are produced by removing columns of atoms along [001] direction from a crystalline Si structure and the pores surfaces are passivated by hydrogen atoms for the electronic band structure calculations. This supercell model emphasizes the interconnection between silicon nanocrystals, delocalizing the electronic and phononic states. However, the results of both elementary excitations show a clear quantum confinement signature, which is contrasted with that of nanowire systems. In addition, ab-initio calculations of small supercells are performed in order to verify the tight-binding results. The calculated dielectric function is compared with experimental data. Finally, a shift of the highest-frequency Raman peak towards lower energy is observed, in agreement with the experimental data.