SiO2 films containing Si nanocrystals (nc-Si) and Er were prepared and their photoluminescence (PL) properties were studied. The samples exhibited luminescence peaks at 0.81 and 1.54 μm, which could be assigned to the electron-hole recombination in nc-Si and the intra-4f transition in Er3+, respectively. Correlation between the intensities of the two luminescence peaks was studied as functions of Er concentration and excitation power. The present results clearly demonstrate that excitation of Er3+ occurs through the recombination of photogenerated carriers spatially confined in nc-Si and the subsequent energy transfer to Er3+.

1.54 μm photoluminescence of Er3+ doped into SiO2 films containing Si nanocrystals: Evidence for energy transfer from Si nanocrystals to Er3+

Surface chemistry of Luminescent Silicon Nanocrystallites

SiO2 films containing Si nanocrystals (nc-Si) and Er were prepared and their photoluminescence (PL) properties were studied. The samples exhibited PL peaks at 0.8 and 1.54 μm, which could be assigned to the electron-hole recombination in nc-Si and the intra-4f transition in Er3+, respectively. Correlation between the intensities of the two PL peaks was studied as functions of the size of nc-Si, Er concentration, excitation power and excitation wavelength. It was found that the 1.54 μm PL of Er3+ is strongly enhanced by incorporating nc-Si in films. Furthermore, the intensity of the 1.54 μm peak was found to depend strongly on the size of the incorporated nc-Si.

Photoluminescence from SiO2 films containing Si nanocrystals and Er: Effects of nanocrystalline size on the photoluminescence efficiency of Er3+

We describe the increase of europium ion (Eu3+) fluorescence owing to resonant plasma oscillation of silver (Ag) particles in silica (SiO2) glass, which were precipitated by annealing in a reducing atmosphere sol–gel derived SiO2 glass containing Ag+ and Eu3+ ions. Nanometer size effects of Ag particles on the increase were also investigated as a function of the reduction time. The mean particle size and the volume fraction of silver particles in glass were estimated from absorption spectra using the Mie–Drude theory modified by the electron mean free path model. The fluorescence from Eu3+ ions when the excitation was a N2 laser increased in the presence of silver particles of ∼4.3 nm size. From comparison of the radiative damping time of the plasma oscillation with the lifetime of Eu3+ fluorescence we, tentatively, concluded that the induced surface plasma oscillation by incidence and the interaction between Eu3+ and Ag particles occurred simultaneously.

Enhanced fluorescence from Eu3+ owing to surface plasma oscillation of silver particles in glass

Photonic crystals based on silica colloidal crystals (artificial opals) exhibit pronounced stopbands for electromagnetic wave propagation and the corresponding modification of the photon density of states in the visible range. These spectrally selective features can be enhanced by impregnating opals with higher refractive materials like, e.g., polymers. Doping of these structures with dye molecules, semiconductor nanoparticles (quantum dots), and rare-earth ions provides a possibility to examine the challenging theoretical predictions of the inhibited spontaneous emission in photonic bandgap (PBG) materials. First experiments are discussed in which pronounced modification of spontaneous emission spectra and noticeable changes in decay kinetics were observed.

Spontaneous emission of dye molecules, semiconductor nanocrystals, and rare-earth ions in opal-based photonic crystals

Erbium photoluminescence at room temperature and at 77 K has been observed from porous silicon doped with erbium from a spin‐on silica gel film. Erbium incorporation into silicon dioxide at the surface of porous silicon and rapid thermal processing at temperatures higher than 1223 K were found to be a necessary prerequisite for erbium‐related luminescence in porous silicon. No erbium diffusion into monocrystalline silicon from the spin‐on films was observed. The depth‐dependent erbium concentration in the bulk of porous silicon was determined by secondary‐neutral‐ and secondary‐ion‐mass spectrometry depth profiling. The laterally resolved erbium distribution in the porous silicon was derived from energy‐dispersive x‐ray analysis. Possible mechanisms of erbium‐related luminescence in porous silicon are discussed.

G. N. Troyanova

Papers

Erbium luminescence in porous silicon doped from spin‐on films

Strong 1.54 μm luminescence from erbium-doped porous silicon

Porous silicon as low-dimensional host material for erbium-doped structures

Luminescence of erbium-doped porous silicon

Heteroepitaxial growth of lead sulfide on silicon