In this study, the structural properties of luminescent porous silicon layers have been investigated. Double x-ray and electron diffraction patterns combined with high resolution electron microscopy (HREM) show a good agreement in that the distortion of the lattice planes in porous silicon is related to the smallness of the crystallites constituting the layers. HREM results indicate that a two-level microstructure is present in porous silicon layers. This structure consists of a crystalline part (nanocrystals) and an amorphous part (a sponge-like structure). The morphology of both parts show differences for samples grown under different conditions. A model based on this two-level microstructure is used to account for these observations. It turns out that this microstructure cannot be characterized, as often attempted, by only the measured values of the porosity and the surface area. Finally, double x-ray diffraction on post-treated porous silicon layers confirms that hydrogen desorption and readsorption or further oxidation and/or reconstruction of the oxide layer in porous silicon induce further distortion of the lattice planes. © 1995, The Electrochemical Society, Inc. All rights reserved.

Sharp luminescence at 1.54μm from erbium doped porous silicon has been observed. The silicon was made porous after implantation of high doses of erbium and oxygen into p-type Czochralski silicon. The erbium related luminescence from porous silicon is an order of magnitude more intense than that from erbium doped single crystal silicon. © 1995, IEE. All rights reserved.

It has been postulated that light emission from porous silicon is caused by quantum confinement of the electron states within silicon wires formed by anodic electroetching of silicon. In order to investigate this hypothesis we have made measurements of the X-ray excited optical luminescence (XEOL) and the total electron yield (TEY) as a function of X-ray energy for porous silicon at station 3.4 of the SRS at Daresbury laboratory. Results have shown that the luminescence is associated with elemental silicon, and this is true for as prepared and oxidised material. In the latter case the XEOL spectrum is completely different from the TEY. However, by considering the microscopic origin of the excitation together with time-dependent relaxation data, we conclude that the emission comes from silicon surface states and not quantum effects in the nanoparticles. This is in contrast to other similar studies. © 1995.

The structural and optical properties of low and high porosity luminescent porous silicon layers have been studied. It has been shown that the luminescence intensity is strongly dependent on the porosity and not on the surface area. Double-crystal X-ray and electron diffraction patterns indicate that freshly anodized luminescent porous silicon is crystalline. Both techniques show an increasing distortion of the lattice planes with increasing porosity, implying that the distortion is strongly linked to the smallness of the crystallites constituting the layers. © 1995.

High resolution scanning transmission electron microscopy (STEM) and synchrotron X‐ray excitation of luminescence (XEOL) is used to probe the chemical nature of the luminescence mechanisms of porous and rapidly oxidised porous silicon. It is concluded that for fresh porous silicon, Si‐Si bonded material is involved in the luminescence. For oxidised material this is probably not the case, the chemical environment being SiO2. Copyright © 1995 WILEY‐VCH Verlag GmbH & Co. KGaA