Photoluminescence of Si nanocrystals embedded in : Excitation/emission mapping

Abstract

Time‐resolved photoluminescence from Si nanocrystals produced by 1100∘C thermal annealing of SiOx/SiO2 multilayers were investigated by tunable laser excitation, achieving a detailed excitation/emission pattern in the visible and UV range. The emission lineshape is a gaussian curve inhomogenously broadened because of the size distribution of Si nanocrystals, the excitation spectrum consists of the overlap of two gaussian bands centered around 3.4 and 5.1 eV. The mapping of luminescence spectral components with the lifetime points out the energy cubic dependence of the spontaneous emission rate. These findings are interpreted on the basis of models proposed in literature that associate this luminescence with quantum confinement of excitons or interfacial Si/SiO2 defects.

Effect of the structure on luminescent characteristics of SRO-based light emitting capacitors

“…Figure 2(b) shows the PLE spectra of the SRO 20 films, where two main peaks at about 290 and 360 nm are observed. Excitation bands at ∼360 and ∼290 nm have been related to Γ 25 →Γ 15 and Γ 25 →Γ 2′ optical direct transitions in bulk silicon, respectively [20][21][22][23]. As observed in figure 2(b), there is a clear blue-shift of the PLE band related to the Γ 25 →Γ 2′ direct transition as the annealing temperature increases.…”

“…For the SRO 20 films, the PL intensity increases as the annealing temperature increases, with the highest emission obtained for the one thermally annealed at 1100 °C. The red-shift of the main PL peak has been widely observed and is ascribed to the agglomeration of excess silicon and subsequent silicon nanoparticle formation as a result of the thermal annealing process [4,16,19,20]. Nevertheless, besides the Si agglomeration, some point defects can also exist within the SRO films.…”

Si and Ge nanocrystals in resonator multilayer structures

“…Figure shows PL decay curves of the SiO x /Al 2 O 3 bare structure taken at different pump intensities in the range 7–4000 µW that corresponds to the linear mode . The decay curves have been measured at 1.70 eV, i.e., at the maximum of the PL peak.…”

Visible luminescence peculiar to sintered silica nanoparticles: Spectral and decay properties

“…An interesting suggestion derives from past studies performed on γ-irradiated oxygen deficient silica where a PL around 1.8 eV has been observed under 2.5 eV excitation; this PL has been associated with highly oxygen deficient states due to Si clusters [28]. This attribution is justified by the knowledge of the extensively investigated Si-nanocrystals embedded in silica which are characterized by a red PL: its position depends on the crystal size, its lifetime occurs in the μs timescale and its PLE extends in the visible-UV range [29][30][31][32]. This emission is attributed to both the quantum confinement of excitons and localized defects states at the Si/SiO 2 interface [33,34].…”