Formation of Si nanocrystallites observed by in situ transmission electron microscopy and their effect on the enhancement of Er photoluminescence in Er-doped SiO2

Abstract

The formation of Si nanocrystallites ͑nc-Si͒ in erbium ͑Er͒-dispersed SiO x ͑x ഛ 2͒ films was investigated by in situ annealing while performing transmission electron microscopy measurements. The correlation between the formation of nc-Si and Er ion emissions was also comprehensively investigated by photoluminescence and electron spin resonance measurements. The results showed that the formation of nano-Si region with the suitable size is important for enhancement of Er ion emission.

The evolution of the fraction of Er ions sensitized by Si nanostructures in silicon-rich silicon oxide thin films

“…We note that the values measured here are in good agreement with previously reported results [4,15] where Si-ncs density varies from 1.3 × 10 19 to 2 × 10 18 cm −3 for T a varying between 400 and 1100 • C. 2 × 10 18 ph cm −2 s −1 . The PL intensity increases between 500 and 600 • C for samples B and C, then decreases by a factor of 2 (sample B) and 3 (sample C) from 600 to 850 • C. It further decreases by a factor of 5 for T a higher than 850 • C. On the other hand, the PL intensity of sample A, with the lowest Er concentration, slightly increases from 500 to 700 • C, then decreases by a factor of 2.7 for T a higher than 850 • C. This result, in good agreement with the previously reported results for such matrices [16,17], has been attributed either to the decrease of the Si sensitizer density or Er clustering or cooperative up-conversion for high T a and high C Er . We note that the decrease by a factor of 3 of the density of Sincs between 850 and 1050 • C, as observed by EFTEM, could partially explain the evolution of the PL intensity with T a .…”

“…The inset of figure 2 shows the typical PL spectra of Er 3+ ions in the SiO layer deposited under NH 3 before and after annealing. The excitation photon flux at 364 nm was On the other hand, the PL intensity of sample A, with the lowest Er concentration, slightly increases from 500 to 700 • C, then decreases by a factor of 2.7 for T a higher than 850 • C. This result, in good agreement with the previously reported results for such matrices [16,17], has been attributed either to the decrease of the Si sensitizer density or Er clustering or cooperative up-conversion for high T a and high C Er . We note that the decrease by a factor of 3 of the density of Sincs between 850 and 1050 • C, as observed by EFTEM, could partially explain the evolution of the PL intensity with T a .…”

From amorphous to crystalline silicon nanoclusters: structural effects on exciton properties

“…Luminescence in the visible, however, is often observed to appear and to evolve in correlation with Si-ncls formation and growth, as is expected from quantum confinement (QC) of excitons in crystalline Si-ncls [17,18], albeit its specific origin is still a matter of active discussion in the literature [19]. The thermally induced formation of Si-ncls has been shown to be also a very important step for the sensitization of erbium light emission from erbium-doped SRSO [20]. It is thus remarkable that after more than a decade of studies, many aspects of the microscopic mechanisms of Si nanocrystal formation, and the relation between the structural properties of the material and its optical characteristics, are still poorly understood.…”