Optical and structural properties of SiO2 co-doped with Si-nc and Er3+ ions
Résumé
We present a study on erbium-doped silicon rich silicon oxide (SRSO:Er) thin films grown by the magnetron cosputtering of a three confocal cathodes according to the deposition temperature and the annealing treatment. It is shown that several parameters such as the stoichiometry SiOx, the Erbium content and the fraction of agglomerated Silicon are strongly influenced by the deposition temperature. Especially, an increase of the fraction of agglomerated-Si concomitant to a reduction of the erbium content is observed when the deposition temperature is raised. These structural differences have some repercussions on the optical properties that lead to better performances for high-temperature deposited material. It is illustrated by the Er-PL efficiency that is higher for 500°C-deposited than for RT-deposited sample at all annealing temperatures. Finally an investigation of the different emitting centres within the films is performed with a cathodoluminescence technique to highlight the emission of optically-active defect centers in the matrix. It is shown that some oxygen vacancies, namely Silicon-Oxygen Deficient Centers, have a strong contribution around 450-500 nm and are suspected to contribute to the energy transfer towards Er3+ ions.