Lu Jin

Structure and luminescence evolution of annealed Europium-doped silicon oxides films

Europium (Eu)-doped silicon oxide films with Eu concentrations from 2.1 to 4.7 at. % were deposited by electron beam evaporation. The Eu related luminescence from the films was found to be sensitive to the evolution of film microstructures at different annealing temperatures. Luminescence centers in the films changed from defects of silicon oxides to 4f(6)5d-4f(7)(8S(7/2)) transition of Eu2+ after the films annealed in N2 at temperature higher than 800 °C. The evolution of luminescence centers was attributed to the formation of europium silicate (EuSiO3), which was confirmed by x-ray photoelectron spectroscopy, x-ray diffraction, time resolved photoluminescence, and transmission electron microscopy.

Energy transfer from luminescent centers to Er3+ in erbium-doped silicon-rich oxide films

The energy transfer mechanism between luminescent centers (LCs) and Er3+ in erbium-doped silicon-rich oxide (SROEr) films prepared by electron beam evaporation is investigated. Intense photoluminescence of the LCs (weak oxygen bonds, neutral oxygen vacancies, and Si=O states) within the active matrixes is obtained. Fast energy transfer from Si=O states to Er3+ takes advantage in the SROEr film and enhances the light emission from Er3+. The introduction of Si nanoclusters, which induces the Si=O states and facilitates the photon absorption of the Si=O states, is essential to obtain intense photoluminescence from both Si=O states and Er3+.

Sensitization of Er 3+ ions in silicon rich oxynitride films: effect of thermal treatments

The optical properties of reactive co-sputtered erbium doped silicon rich oxynitride (Er:SRON) films are studied as a function of annealing temperatures (Ta). The sensitization mechanism of Er3+ is found to evolve with Ta: excess Si related localized states play the essential role in samples when Ta is below 700 °C, while silicon nanoclusters (Si-NCs) become the dominate sensitizers when Ta exceeds 800 °C. Our results show that higher density of sensitized Er3+ could be acquired via energy transfer from localized states, and thus provide an alternative way for the engineering of light sources based on Er:SRON.

The modulation on luminescence of Er3+-doped silicon-rich oxide films by the structure evolution of silicon nanoclusters

A series of silicon-rich oxide (SRO) and erbium-doped SRO (SROEr) films imbedded with structural tunable silicon nanoclusters (Si NCs) have been fabricated using sputtering followed by post-annealing. The coalescence of Si NCs is found in the films with large Si excess. The energy transfer rate between Si NCs and Er3+ is enhanced, but the luminescence efficiencies of both Si NCs and Er3+ are reduced by the coalescent microstructures. Optimization of the microstructures of Si NCs is performed, and the preferential optical performance for both Si NCs and Er3+ could be achieved when Si NCs were separated in microstructures.

Size-dependent coupling between localized surface plasmons and excitons in silicon nitride matrix

The size-dependent coupling between localized surface plasmons (LSPs) and excitons within a silicon nitride (SiN(x)) matrix is investigated. A strong correlation between the photoluminescence (PL) enhancement and this resonance coupling is observed. From the analysis of the relationship between the dipolar resonance peaks of Ag nanostructures with various sizes and those of PL enhancement, we ascribe the enhancement of PL from the SiN(x) matrix by the addition of Ag nanostructures mainly to the LSP resonance coupling.

Temperature dependence of sensitized Er3+ luminescence in silicon-rich oxynitride films

The temperature dependence of sensitized Er3+ emission via localized states and silicon nanoclusters has been studied to get an insight into the excitation and de-excitation processes in silicon-rich oxynitride films. The thermal quenching of Er3+ luminescence is elucidated by terms of decay time and effective excitation cross section. The temperature quenching of Er3+ decay time demonstrates the presence of non-radiative trap states, whose density and energy gap between Er3+4I13/2 excited levels are reduced by high-temperature annealing. The effective excitation cross section initially increases and eventually decreases with temperature, indicating that the energy transfer process is phonon assisted in both samples.

Optimization of the electroluminescence from SiNx-based light-emitting devices by modulating the size and morphology of silver nanostructures.

A maximal enhancement of ~6.5 times of the external quantum efficiency (EQE) for SiNx-based light-emitting devices (LEDs) is achieved by magnetron sputtering a silver nanostructures layer onto the active matrix. The enhancement of EQE is affected by the dimension and morphology of silver nanostructures, which can be controlled by the sputtering time and the post treatment of rapid thermal annealing. The optimal size of silver nanostructures is about 100 nm in diameter by comparing the integrated electroluminescence intensity under the same input power. The optimization of EQE for SiNx-based LEDs is discussed by considering the contributions of the enhancement of light-extraction efficiency induced by the surface roughening of the front electrode, internal quantum efficiency due to the coupling between excitons and localized surface plasmons, and carrier injection efficiency. Our work may provide an alternative approach for the fabrication of Si-based light sources with promising luminescence efficiency.

Evolution of the sensitized Er3+ emission by silicon nanoclusters and luminescence centers in silicon-rich silica

The structural and optical properties of erbium-doped silicon-rich silica samples containing different Si concentrations are studied. Intense photoluminescence (PL) from luminescence centers (LCs) and silicon nanoclusters (Si NCs), which evolves with annealing temperatures, is obtained. By modulating the silicon concentrations in samples, the main sensitizers of Er3+ ions can be tuned from Si NCs to LCs. Optimum Er3+ PL, with an enhancement of more than two, is obtained in the samples with a medium Si concentration, where the sensitization from Si NCs and LCs coexists.

Photoluminescence from dislocations in silicon induced by irradiation of electron beams

We induced dislocations controllably by using irradiation of electron beam. The dislocations induced by irradiation slipped though whole wafer and well-distributed at its slipping direction {111} <100> with a density highest to ∼1.3×107 cm−2. And dislocations related luminescence (DRL) peaks from D1 to D4 were observed in the irradiated silicon. This method may lead to the silicon based light emitting device with the compatibility of integrated circuit technology.

Surface plasmon enhanced electroluminescence of SiNx film based MIS device

Electroluminescence of MIS devices consisted with an ITO/SiO2/SiNx/Ag/p-Si/Al multilayer structure, as well as the multilayer without Ag, was investigated. The enhancement of EL intensity of MIS devices by introduce an Ag islands film was observed. Due to the existence of Ag islands film in the MIS devices of SiNx films, the injected current of MIS devices was increased and the extracted EL was also enhanced by the excitons-LSPs coupling.