The temperature dependence of the viscosity and stressrelaxation kinetics of sol-gel-derived SiOC glasses that contain up to 14 at.% carbon have been characterized in the temperature range of 1000°-1400°C. The viscosity, as determined from relaxation experiments, is in good agreement with the creep viscosity and is typically two orders of magnitude higher than the viscosity of vitreous silica. However, materials suffer from partial crystallization at >1150°C, and the precipitation of ␤-SiC nanocrystals induces a flow-hardening behavior and results in a dynamic increase in viscosity, especially at >1200°C and for glasses with a high carbon content.

The present article deals with the optimized processing conditions leading to the highest density of Si nanoclusters which play the role of sensitizing centers for the nearby Er ions within a silica matrix. The layers were obtained by reactive magnetron sputtering under a plasma of Ar mixed to different rates of hydrogen, and were subsequently annealed at various temperatures. The increase of the dilution degree of the Ar plasma with hydrogen was found to multiply the nucleation sites whose density foreshadows that of the Si nanoclusters formed upon annealing. Both hydrogen content and annealing temperature govern the growth of the clusters. The maximum density of efficient sensitizing centers was obtained for hydrogen rate in the plasma of 50% and annealing at 900 °C. This has directly led to the enhancement of the coupling rate between the Si nanoclusters and the Er ions, as reflected by the ten times increase of the proportion of optically active ions, compared to that for standard conditions. In parallel, the lifetime emission of the active Er ions was found to continuously improve with the annealing temperature and has reached values exceeding 7 ms.

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Room-temperature 1.54 μm electroluminescence from Er-doped silicon-rich silicon oxide films deposited on n + -Si substrates by magnetron sputtering J. Appl. Phys. 90, 5835 (2001); 10.1063/1.1413231Effect of hydrogenation on room-temperature 1.54 μm Er 3+ photoluminescent properties of erbium-doped silicon-rich silicon oxide Er-doped Si-rich silica layers were obtained by reactive magnetron sputtering and both structural and room-temperature photoluminescence properties were investigated. The controlled introduction of hydrogen in the plasma was found to play a critical role in the microstructure and distribution of the Si nanograins formed after annealing. Concomitant density increase and size decrease of these nanograins mostly amorphous were noticed upon increasing the hydrogen partial pressure in the plasma. This was accompanied by a systematic enhancement of the Er emission indicating that both crystallized and amorphous silicon nanoparticles are similarly efficient sensitizers for Er emission. The lifetime of the latter was found as high as 5-6 ms.