A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.

The structural and luminescence properties of porous silicon

Organometallic chemistry on silicon and germanium surfaces.

The current status of the use of nanoparticles for photothermal treatments is reviewed in detail. The different families of heating nanoparticles are described paying special attention to the physical mechanisms at the root of the light-to-heat conversion processes. The heating efficiencies and spectral working ranges are listed and compared. The most important results obtained in both in vivo and in vitro nanoparticle assisted photothermal treatments are summarized. The advantages and disadvantages of the different heating nanoparticles are discussed.

Nanoparticles for photothermal therapies.

http://nathan.instras.com/documentDB/paper-69.pdf

Porous silicon: a quantum sponge structure for silicon based optoelectronics

This review is concerned with quantum confinement effects in low-dimensional semiconductor systems. The emphasis is on the optical properties, including luminescence, of nanometre-sized microcrysta...

Low-dimensional systems: quantum size effects and electronic properties of semiconductor microcrystallites (zero-dimensional systems) and some quasi-two-dimensional systems

Porous silicon/silicon structures under anodic oxidation conditions give rise to an electroluminescence phenomenon in the visible range. Using an optical multichannel analyzer the spectral distribution of the emitted light was measured−in situ−during the anodic oxidation step. Recorded spectra show a maximum which shifts continuously from red‐orange at the beginning of the process towards the yellow range. The visible emission well above the band gap of bulk silicon is attributed to a quantum size effect in the very small size (5–20 A) silicon island which constitutes the porous silicon skeleton. The light emission is interrupted when the current flow stops due to the formation of a continuous oxide layer at the porous silicon/silicon interface.

Electroluminescence in the visible range during anodic oxidation of porous silicon films

This study presents optical transmission measurements performed on free‐standing homogeneous porous silicon (PS) films of different porosities and substrate doping levels. The absorption coefficient curves deduced from these measurements, taking into account the total quantity of matter in the PS film, exhibit significant blue shift (up to 500 meV). These shifts, well correlated with the crystallite size variations with porosity and substrate doping observed by electron microscopy and gas adsorption experiments, are attributed to quantum size effects in the silicon microcrystallites.

Optical absorption evidence of a quantum size effect in porous silicon

We present results of photoluminescence experiments performed at 2 and 300 K on porous silicon layers with different porosities. The samples are obtained by electrochemical dissolution of (100) silicon wafers in hydrofluoric solution. The energy of the photoluminescence and its variation with porosity are found in good agreement with a theoretical model of quantum confinement in Si quantum wires. Electrons have to be taken into account, but it is shown that this quantum effect is mainly due (≊60%) to the large confinement of holes.

Visible photoluminescence from porous silicon: A quantum confinement effect mainly due to holes?

Optical characterisation of porous silicon layers by spectrometric ellipsometry in the 1.5–5 eV range

Epitaxial silicon films are obtained by low temperature chemical vapor deposition on porous silicon layers (PSL). The PSL are formed on lightly and highly boron doped silicon substrates. In the case of lightly doped substrates, the epitaxial films exhibit a large defect density (10 10 cm -2 ). It is shown that this defect density can be reduced by a 10 2 to 10 3 factor through the use of silicon channeled implantation and subsequent thermal annealing. On the other hand, when the epitaxial growth is performed on PSL formed from highly doped boron substrates, the epitaxial quality of the resulting films is equivalent to the homoepitaxy of silicon on bare silicon

http://jes.ecsdl.org/content/139/12/3595.full.pdf

A. Halimaoui

Papers

Electroluminescence in the visible range during anodic oxidation of porous silicon films

Optical absorption evidence of a quantum size effect in porous silicon

Visible photoluminescence from porous silicon: A quantum confinement effect mainly due to holes?

Optical characterisation of porous silicon layers by spectrometric ellipsometry in the 1.5–5 eV range

Silicon on Insulator Structures Obtained by Epitaxial Growth of Silicon over Porous Silicon