Abdelillah Slaoui

Correlation of structural properties with energy transfer of Eu-doped ZnO thin films prepared by sol-gel process and magnetron reactive sputtering.

We investigated the structural and optical properties of Eu-doped ZnO thin films made by sol-gel technique and magnetron reactive sputtering on Si (100) substrate. The films elaborated by sol-gel process are polycrystalline while the films made by sputtering show a strongly textured growth along the c-axis. X-ray diffraction patterns and transmission electron microscopy analysis show that all samples are free of spurious phases. The presence of Eu(2+) and Eu(3+) into the ZnO matrix has been confirmed by x-ray photoemission spectroscopy. This means that a small fraction of Europium substitutes Zn(2+) as Eu(2+) into the ZnO matrix; the rest of Eu being in the trivalent state. This is probably due to the formation of Eu(2)O(3) oxide at the surface of ZnO particles. This is at the origin of the strong photoluminescence band observed at 2 eV, which is characteristic of the (5)D(0)-->(7)F(2) Eu(3+) transition. In addition the photoluminescence excitonic spectra showed efficient energy transfer from the ZnO matrix to the Eu(3+) ion, which is qualitatively similar for both films although the sputtered films have a better structural quality compared to the sol-gel process grown films.

Studies of silicon nanocrystals in phosphorus rich SiO2 matrices

Abstract In this contribution we present a new type of optoelectronic silicon nanocrystal (Si-nc) based material, namely, Si-nc embedded into solidified pure or doped spin-on-glasses. The resulting self-supporting samples contain thin layers with high Si-nc concentrations. The visible photoluminescence (PL) maximum at room temperature is blue-shifted when the concentration of phosphorus in the spin-on-glass is increased.

Si Nanocrystals Embedded in a Silicon Oxynitride Matrix

We investigated the morphological and structural change in silicon nanostructures embedded in the silicon oxynitride matrix. The study has been carried out on thin films thermally annealed at high temperature, after deposition at 400°C by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapour Deposition (ECR- PECVD), under different deposition parameters. Our study evidenced the existence of a well defined threshold for the silicon content in the film (around 47%), to get Si nano-crystallization in the silicon oxynitride matrix. Both Si nano-crystals and Si nano-columns have been observed by TEM analysis in two samples having a similar Si content but deposited under different conditions.