Fine Structure of Visible Light Emitting Porous Silicon

Abstract

ABSTRACTPorous Si formed by anodization is studied by means of high-resolution scanning electron microscopy, optical microscopy, micro-photoluminescence spectroscopy, high-resolution transmisson electron microscopy, and micro-Raman spectroscopy. Surface morphologies of porous Si films are varied by changing the anodization conditions. High-resolution scanning electron microscopy measurements show that in all these films, porous Si fine structures of visible photoluminescent regions, which are confirmed with optical microscopy and micro-photoluminescence spectroscopy, are composed of particlelike structure of various sizes from several nm to several tens of nm. Transmission electron microscopy shows that these particles are composed of single-crystal Si spheres covered with an oxide layer. The peak of the Raman spectrum from the particlelike structure is shifted to lower energy and is wider than that for bulk Si, possibly due to lattice expansion around large surface fractions. These results suggest that the effective photoluminescence of porous Si is due to three-dimensional carrier confinement in quantum boxes.