Structural and optical study of Ce segregation in Ce-doped SiO1.5 thin films

Abstract

Cerium doped SiO 1.5 thin films fabricated by evaporation and containing silicon nanocrystals were investigated by atom probe tomography. The effect of post-growth annealing treatment has been systematically studied to correlate the structural properties obtained by atom probe tomography to the optical properties measured by photoluminescence spectroscopy. The atom probe results demonstrated the formation of Ce-Si rich clusters upon annealing at 900 C which leads to a drastic decrease of the Ce-related luminescence. At 1100 C, pure Si nanocrystals and optically active cerium silicate compounds are formed. Consequently, the Ce-related luminescence is found to re-appear at this temperature while no Si-nanocrystal related luminescence is observed for films containing more than 3% Ce. V C 2015 AIP Publishing LLC. [http://dx.

On the interplay between Si-Er-O segregation and erbium silicate (Er2Si2O7) formation in Er-doped SiOx thin films

“…We can directly evidence that annealing at 1100 + C during 1 h induces the diffusion and the precipitation of all Si atoms in excess and a part of Er ions. The observed nanostructure is very similar to that observed in Ce-doped SiO 1.5 thin films [14,23].…”

“…By counting the number of atoms of each species in the sampling box, we are able to identify the composition of the Er-rich nanoparticles. The resulting compositional measurements are listed in [14,24]. This important result demonstrates similar phase transformation characteristics for two different rare earths in silicon-enriched silica.…”

“…The presence of crystallized Si-ncs has been evidenced by HRTEM since 900 + C (not presented here). In addition, it has been also highlighted that, for high concentrations, rare earth ions may also exhibit inhomogeneity upon deposition [14]. Moreover, as proposed by the mixture model [15] and recently evidenced by XPS [16], oxygen can be in homogenously distributed in SRSO layers, thus leading to the formation of Oxygen-rich and Oxygen-poor network.…”

The nitrogen concentration effect on Ce doped SiOxNy emission: towards optimized Ce3+ for LED applications

“…39 Concerning the Ce doping, the same clustering effect has been observed at T A =900°C in SiO 1.5 . 19,35,40 However, in the present study, all the HRTEM images do not show lattice fringes and very diffuse rings characteristic of amorphous materials are observed in the FFT images. In other words, no trace of Ce clustering effect has been detected in any film annealed at 700 °C or 900 °C.…”

“…Finally, the modeling demonstrates that with a N 2 flux below 2 sccm, a Si "phase" is present and likely kills the expected luminescence of Ce ions, as observed previously for enriched Ce-doped SiO 1.5 films on Si. 40 The γ scenario mentioned above in the optical analysis part, involving the surrounding media of Ce, is then confirmed. For 2 sccm, the samples contain mainly two phases (Si 3 N 4 and SiO 2 ) which exhibit a Ce PL signal since no free Si phase is detected.…”