Abstract
Porous Si (PS) layers emitting red photoluminescence (PL) are prepared by anodization of p-type (100) monocrystalline Si substrate in aqueous HF solutions. PS layers oxidized in free air exhibit an intense yellow-orange PL under uv photoirradiation, while as-prepared samples emit red PL. Authors explain the PL behaviour and its origin in both unetched and HF-etched as- prepared and oxidized PS layers according to calculated PL based on quantum confinement formalism and ir spectroscopy. PL behaviour is associated with a quantum size effect and concentration change in quantum dots and wires. HF etching of oxidized PS may induce dots or wires in the PS structure, depending on the oxidation degree, and produce a PL blue- or redshift, resp. By correlating PL spectra of unetched and HF-etched oxidized PS, authors find that highly oxidized PS transforms into an SiO2 matrix in which photoluminescent nanocrystalline Si quantum dots are embedded. 32 refs.