Porous Silicon Science and Technology

Optical Properties of Low Dimensional Silicon Structures, 1993

We present the mechanical, electrical and optical properties of light emitting porous silicon (LEPOS) prepared under clean conditions. It was found that the asanodised layers are in a compressive state, and that after annealing the stress changes and plastic deformation takes place. The film resistivities are greater than 10 7 il-cm. Photoluminescence stability from LEPOS is demonstrated on the scale of months. Finally, we present our measurements of the reflectance of porous Si on crystalline Si and show that it is very low over a wide spectral range.

International Journal of Nanotechnology, 2011

Electrochemical etching-a usual technique in nanotechnology-creates porous silicon with novel and useful properties. The considerable and controllable changes in the electronic structure and refractive index of porous silicon make it a promising material for photonics in comparison with bulk silicon. In this paper, we review as well as report on some interesting and unique properties of porous silicon material. In studying porous silicon as a low-dimensional material, we focus on the effect of the surface passivation of silicon nanocrystals on photoluminescence characteristics of such zero-dimensional crystals. As an optical material, we demonstrate the fabrication method and optical properties of the planar waveguide as well as the active waveguide and optical interference filters operated in infrared wavelengths. In addition, we investigated the effect of energy transfer from silicon nanocrystals to erbium ions in the erbium-doped porous silicon waveguide and also elaborate on the origins of the difference between the reflectivity spectra from fabricated filters and that of the simulation program.

Materials Chemistry and Physics, 1993

Visible light emission in porous silicon is of current interest both scientifically and technologically. Since this system can exhibit a wide variety of structures and particle sizes, however, a large volume of data exists, which at times can be quite contradictory. In this paper, a review of the general properties of porous silicon that have been reported thus far will be given, along with a discussion of the possible mechanisms for the luminescence process. The model of quantum confinement, amorphous silicon luminescence, a polysilane mechanism and the siloxene model will be discussed, along with the support for and drawbacks of each particular model.

Applied Surface Science, 1993

Following the recent discovery of visible photo and electroluminescence of high-porosity porous silicon layers this paper presents a review of the most relevant results and models proposed to explain the phenomena. Porous silicon fabrication techniques are presented including some recommendations to allow a meaningful comparison of results obtained hy different laboratories. Recent results of pore size. surface area measurements. crystallographic structure determination and microstructure observations are discussed. Detailed studies of optical absorption coefficients of porous layers of different porosities are pt-esentetf. A clear upshift toward the visible range is explained by a quantum confinement model. Intense visible photoluminesccnce ol porous silicon layers is discussed on the ground of both quantum confinement and surface-controlled phenomena. The caaential role played by surface passivation, for efficient luminescence. is analysed. Reported results of visible electroluminescence during anodic oxidation of porous silicon layers and visible light emission from solid-state porous silicon dcviccs are reviewed.

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Journal of Molecular Structure, 1999

Spectroellipsometrical (SE) investigations in 1.5-4.0 eV spectral range were done for optical characterization of porous silicon (PS) thin films. A mixing of a crystalline silicon and amorphous silicon with voids using Effective Medium Approximation [D.E. Aspnes, Phys. Rev. B 27 (1983) 985] is used to calculated the refraction index (n) and the absorption constant (k) of the PS layers. Measurements were done on PS obtained electrochemically on p ϩ silicon substrates. From the dispersion spectra of the refractive index, using the Wemple DiDomenico model [S.H. Wemple, M. DiDomenico Jr., Phys. Rev. B 3 (1971) 41338], the values for optical band gap, energy oscillator and dispersion energy for PS (model's parameters introduced by Wemple) are evaluated.

MRS Proceedings, 1994

ABSTRACTPorous silicon (PS) has been extensively studied in recent years. The origin of its luminescence has been a subject of debate. This work attempts to give some insight towards the understanding of this phenomenon, studying the behaviour of the energy band structure of PS as a function of the pore morphology and distribution, for a given porosity. The porous structure is modeled as empty columns of different sizes and shapes, produced into san otherwise silicon perfect crystal. The columns are passivated with hydrogen atoms. A tight-binding Hamiltonian on an ; sp3:s* basis set is applied onto a supercell. Due to the simplicity of the model, morphology effects can be analyzed. The results show that the band :gap and the nature of the 'States at the top of the valence band depend on the morphology. Furthermore, we also discuss the shift of the conduction band minimum towards the gamma point, producing an almost direct band gap, as the pore distribution changes.

Optical Materials, 2006

In our previous study, the refractive indices of freestanding porous silicon (PS) layers were derived using the envelope method, where the computation is based on the values of local minima and maxima in the oscillations of transmission spectra. In the present work, an improved procedure for calculating the optical parameters from the measurements data is described. It is verified by reflection measurements on freestanding samples that optical scattering at the air-PS interface is the main reason for the loss of the transmitted light intensity and thus for the inaccurate results we obtained earlier by the envelope method. This however can be avoided by taking into consideration the relationship between the optical path in the plane-parallel film and the position of extrema in the transmission spectra. The as-determined effective refractive indices show very good matching with the theoretical calculations by the BruggemanÕs effective medium approximation.

Journal of Physics: Conference Series, 2009

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Bulletin of Materials Science, 1994

Porous silicon prepared with anodic currents of 5 to 30 mA/cm 2 are characterized for structural and electronic properties of surface using photoluminescence, grazing angle X-ray diffraction, photoconductivity, thermally stimulated exo electron emission and work function measurements. The observed results indicate that with increasing porosity the crystallite size decreases and the amount of silicon hydride and oxide-type species increases, exhibiting a tendency similar to that of hydrogenated amorphous silicon and hydrogenated microcrystalline silicon. Free-standing powder of porous silicon, characterized by bright photoluminescenee at 730nm, showed crystallites of nanometre dimensions under the transmission electron microscope.