Study of Structural, Electronic and Vibrational Properties of Porous Silicon with Different Porosity

In this work, density functional theory (DFT) was utilized to study the influence of the porosity on the structural, electronic and vibrational properties of porous silicon (PS). It is based on the potential plane wave (PP-PW) method within generalized gradient approximation (GGA). Supercell model was used to simulate nanopores structures. The results obtained from the formation energy calculation exhibited that the most stable structure corresponds to the highest porosity (40.62%). Moreover, a direct band gap is calculated for all porosities and enlargement of energy gap with porosity was observed. The obtained IR spectra calculation show a resemblance between 15.62 and 40.62% porosities and 3.12 and 28.12% porosities. In order to confirm the theoretical results, we prepared porous silicon specimens by electrochemical etching of (001) p-type silicon wafer (1–10 Ohm cm resistivity). In addition, the IR spectra of PS layers were measured and compared against the calculated spectra. IR absorbance spectrum obtained for a porosity of 40.62% shows great agreement with the experimental one and confirms that the surface is hydrogenated.