Objetivo The fabrication of silicon-based optoelectronic devices is of prime importance for the development of optical interconnects in microelectronics. The recent demonstration that microporous porous silicon (PS) layers are able to produce intense room temperature and visible photo- and electroluminescence (the latter under anodic oxidation conditions), is the first step toward the realisation of silicon emissive devices (light-emitting diodes, lasers, etc). However, the origin of the phenomenon is not yet totally understood. The main goal of EOLIS is to understand this effect through an extensive analysis of various PS layers, and fabrication by sophisticated methods of model structures in the form of dots and wires.A study was made of the mechanisms that give rise to luminescence in silicon nanostructures and in particular in microporous porous silicon (PS) layers. Sample processing: The properties of PS processed by different recipes are being assessed. PS formed in polysilicon layers exhibits a much lower porosity (35%) than layers fabricated, in the same conditions, in monocrystalline substrates (85%) but presents a red luminescence which is much weaker than the latter. PS layers (55% porosity obtained from p-doped substrates), have been stabilized by oxidation at low temperature (300 to 400 C). The results indicate that this treatment does not modify the morphology of PS. Modelling: The electronic properties of thin silicon (111) layers embedded in a calcium fluoride host crystal have been investigated. The band gap is found to increase to the visible range for silicon layer thickness less than 4 double layers (dl). For 1 and 2 dl the bonding silicon-calcium state emerges from the silicon valence band and leads to an almost direct gap at finite wavevectors that could account for efficient luminescence in this system. Calcium fluoride growth on stepped (111) silicon surfaces has been investigated. Observations suggest that the step lattice is not influenced by the fluoride deposit. Characterization: Rapid thermal oxidation (RTO) of PS layers was studied. Aligned crystallites remain throughout oxidized luminescent layers with a wide distribution of size down to below 3 nm. For the highest RTO temperatures, negligible crystalline silicon remains in the layer in accord with the absence of 750 to 800 nm PL emission. In situ atomic force microscopy (AFM) in the contact mode has been carried out on highly porous PS layers. In situ coupled photomodulated infra red (IR) spectroscopy and PL measurements have been carried out on PS layers. Results show that the yellow green luminescence is not only a blue shift of the red luminescence and suggest that it exists 2 different regimes.APPROACH AND METHODS The prime objectives will be to determine the effective dimensionality and degree of quantum confinement in light-emitting porous silicon structures and the role of surface states, dangling bond density and silicon morphology on radiative efficiency. Luminescence measurements made on porous silicon will be compared with those made on epitaxially grown and polymeric silicon structures with well-defined dimensions, crystalline quality and surface states. When combined with theoretical calculations of band structure and oscillator strengths, a model will be built up for the processes giving rise to luminescence in these structures. A wide range of techniques will be required to characterise them. Model dot and wire structures will be fabricated using a variety of techniques which include chemical synthesis, molecular beam epitaxy (MBE), chemical beam epitaxy (CBE) and electron beam and STM lithographies combined with anisotropic etching. The luminescence efficiency of the model structures will be investigated using ex situ and in situ techniques, and compared with theoretical predictions of similar structures. Classical characterisation techniques will include transmission electron microscopy, photoluminescence, electron spin resonance, and atomic force microscopy. These will be combined with novel techniques such as flow microcalorimetry and in situ infrared absorption and photoluminescence to determine the relationship between the radiative efficiency and the nature of the quantum structures. POTENTIAL The know-how gained from these studies will give new insights into the mechanisms giving rise to efficient luminescence in Si material. The knowledge of these mechanisms will allow the fabrication of a new class of silicon devices (light-emitting diodes, lasers). Ámbito científico natural scienceschemical scienceselectrochemistryelectrolysisnatural sciencesphysical sciencesopticsmicroscopyelectron microscopynatural scienceschemical sciencesinorganic chemistrymetalloidsnatural sciencesphysical sciencesopticslaser physicsnatural sciencesmathematicsapplied mathematicsmathematical model Programa(s) FP3-ESPRIT 3 - Specific research and technological development programme (EEC) in the field of information technologies, 1990-1994 Tema(s) Data not available Convocatoria de propuestas Data not available Régimen de financiación Data not available Coordinador CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE Aportación de la UE Sin datos Dirección Campus de Luminy, Case 913 13288 MARSEILLE Francia Ver en el mapa Coste total Sin datos Participantes (6) Ordenar alfabéticamente Ordenar por aportación de la UE Ampliar todo Contraer todo Centre National d'Études des Télécommunications (CNET) Francia Aportación de la UE Sin datos Dirección 98 chemin du Vieux Chêne 38243 Meyland Ver en el mapa Coste total Sin datos Defence Research Agency (DRA) Reino Unido Aportación de la UE Sin datos Dirección St Andrews Road WR14 3PS Malvern Ver en el mapa Coste total Sin datos FORSCHUNGSZENTRUM JUELICH GMBH Alemania Aportación de la UE Sin datos Dirección WILHELM JOHNEN STRASSE 52425 JUELICH Ver en el mapa Enlaces Sitio web Opens in new window Coste total Sin datos LPICM-École Polytechnique (LIX) Francia Aportación de la UE Sin datos Dirección Route de Saclay 91128 Palaiseau Ver en el mapa Coste total Sin datos NATIONAL RESEARCH CENTRE FOR SCIENTIFIC RESEARCH DEMOKRITOS Grecia Aportación de la UE Sin datos Dirección AGHIA PARASKEVI, 60228 15310 ATHENES Ver en el mapa Coste total Sin datos UNIVERSITY OF MODENA AND REGGIO EMILIA Italia Aportación de la UE Sin datos Dirección Via G.Campi 287 41100 MODENA Ver en el mapa Coste total Sin datos