STUDY OF ANODIC-OXIDATION OF POROUS SILICON - RELATION BETWEEN GROWTH AND PHYSICAL-PROPERTIES

In this work, we report a preliminary study of anodic oxidation of p(+) porous silicon in order to obtain Si wires of lateral controlled size. RBS and SIMS spectra show that the whole porous layer is uniformly oxidized independently of the anodic current. The lateral size of Si wires can be controlled by varying the potential difference between the silicon electrode and a platinum cathode from 0 to 10 V. At 10 V, the electrical contact between the substrate and the porous layer is broken. Then the porous layer is practically no more oxidized. At this stage, the lateral size of the Si wire has been estimated to 4 nm. Electron Paramagnetic Resonance (EPR) measurements were performed which indicate that there are oxygen vacancies in SiO2 and that the trigonal (111)P-b center is not the dominating paramagnetic defect as in as-prepared porous layer or in porous layer thermally oxidized. The photoluminescence intensity increases with the potential difference but it is much lower than that obtained in p(+) porous layer of 80% porosity. This weak photoluminescence intensity may be explained by a bad passivation of Si surface or/and to the fact that the major part of the Si wires have lateral size too high to lead to visible luminescence.