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

• Published in: Nanoscale Vol. 1; no. 8; pp. 3823 - 3837
• Main Authors: Ehré, F, Labbé, C, Dufour, C, Jadwisienczak, W. M, Weimmerskirch-Aubatin, J, Portier, X, Doualan, J.-L, Cardin, J, Richard, A. L, Ingram, D. C, Labrugère, C, Gourbilleau, F
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 22.02.2018
• Subjects: Cerium oxides; Clusters; Electron microscopy; Emission analysis; Excitation spectra; Gas flow; Nitrogen; Parameters; Photoluminescence; Silicates; Silicon; Spectrum analysis; X ray photoelectron spectroscopy
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c7nr06139k

Ce-Doped SiO x N y films are deposited by magnetron reactive sputtering from a CeO 2 target under a nitrogen reactive gas atmosphere. Visible photoluminescence measurements regarding the nitrogen gas flow reveal a large emission band centered at 450 nm for a sample deposited under a 2 sccm flow. Special attention is paid to the origin of such an emission at high nitrogen concentration. Different emitting centers are suggested in Ce doped SiO x N y films ( e.g. band tails, CeO 2 , Ce clusters, Ce 3+ ions), with different activation scenarios to explain the luminescence. X-ray photoelectron spectroscopy (XPS) reveals the exclusive presence of Ce 3+ ions whatever the nitrogen or Ce concentrations, while transmission electron microscopy (TEM) shows no clusters or silicates upon high temperature annealing. With the help of photoluminescence excitation spectroscopy (PLE), a wide excitation range from 250 nm up to 400 nm is revealed and various excitations of Ce 3+ ions are proposed involving direct or indirect mechanisms. Nitrogen concentration plays an important role in Ce 3+ emission by modifying Ce surroundings, reducing the Si phase volume in SiO x N y and causing a nephelauxetic effect. Taking into account the optimized nitrogen growth parameters, the Ce concentration is analyzed as a new parameter. Under UV excitation, a strong emission is visible to the naked eye with high Ce 3+ concentration (6 at%). No saturation of the photoluminescence intensity is observed, confirming again the lack of Ce cluster or silicate phase formation due to the nitrogen presence. Ce-Doped SiO x N y films are deposited by magnetron reactive sputtering from a CeO 2 target under a nitrogen reactive gas atmosphere.