Comparative study of photoluminescence of undoped and erbium-doped size-controlled nanocrystalline Si∕SiO2 multilayered structures

Abstract

Spectra and transients of the photoluminescence (PL) of undoped and Er-doped size-controlled nanocrystalline Si/ SiO 2 multilayered structures with mean nanocrystal size of 1.5-4.5 nm have been comparatively investigated. The Er-doped structures exhibit a strong Er-related PL band at 0.81 eV, while the efficiency of the intrinsic PL band of Si nanocrystals at 1.2-1.7 eV decreases by several orders of magnitude in comparison with the undoped structures. At low temperature the PL spectra of the Er-doped structures show several dips separated by the energy of Si TO-phonon and bound to the transition energies between the second and third excited states to the ground state of Er 3+. The Er-related PL is characterized by lifetimes of around 3-5 ms, a weak temperature quenching, and a high efficiency, which is comparable or even stronger than that of the intrinsic PL in the corresponding undoped samples. This efficient sensitizing of the Er-related luminescence is explained by the structural properties of the samples, which favor a strong coupling between the excitons confined in Si nanocrystals and upper excited states of the Er 3+ ions in the SiO 2 matrix.

Enhanced photoluminescence of porous silicon nanoparticles coated by bioresorbable polymers

“…The higher value of β for the coated samples points to a smaller energy dispersion of the defect states. Note that the obtained τ 0 and β values for the coated PSiNPs are close to the corresponding values for highly luminescent nc-Si in SiO 2 matrix formed by high temperature annealing of SiO/SiO 2 structures [32]. This fact confirms the suggestion about perfect passivation of the nonradiative defects in the coated PSiNPs.…”

Photoluminescence and positron annihilation spectroscopy of MeV Si+ ion-irradiated SiyO1−y:Er (y≈1/3) thin films

“…Si nanoclusters ͑Si ncls͒ embedded in a SiO 2 matrix, formed through the thermally induced phase separation of Si atoms in the oxide network, constitute photoluminescence ͑PL͒ centers with broadband aggregate optical emission and absorption properties. 2 While radiative recombination of carriers in a Si ncl can proceed through various channels, excited Si ncls can preferentially couple to nearby Er 3+ ions, 3 which are introduced as a dopant in the oxide matrix by processes such as cosputtering, ion implantation, or metalorganic chemical vapor deposition. This coupling enables nonradiative energy transfer from an excited Si ncl to Er 3+ ions, which ultimately relax by the emission of characteristic luminescence near 1540 nm through one of the various radiative transitions from the 4 I 13/2 manifold to the 4 I 15/2 ͑ground͒ manifold.…”

Photoluminescence of undoped and erbium-doped SiO/SiO/sub 2/ multilayers

“…The PL intensity of this Si-nc line vanishes when Si-nc are coupled to Er ions, on behalf of the intensity of the Er ions signal, which is increased by two orders of magnitude in this case. These points show the coupling effect and the energy transfer between Er ions and the Si-nc [8]. We also notice that the peak of the uncoupled Si-nc is centered around 797 nm, whereas the peak of the Ercoupled Si-nc is centered around 772 nm.…”

“…In the case of the sample containing only Er ions, there is no signal at 800 nm and a small signal is detected at 1540 nm. It is attributed to the 4 I 13/2 → 4 I 15/2 intra-shell Er ion transition [6][7][8]. For the sample containing only Si-nc, a peak is visible at 800 nm.…”

“…The maximum Si-nc size is then equal to the SiO barrier thickness. Such Er-doped multilayer systems can be prepared by RF sputtering [4], magnetron sputtering of Si in vacuum and Er-doped SiO 2 in an oxygen atmosphere [5], reactive magnetron sputtering of SiO 2 and Er 2 O 3 in an hydrogen-argon atmosphere [6] or by evaporation of SiO in an oxygen atmosphere [7,8]. In the last example, Er is introduced by the implantation method.…”