Zhizhong Yuan

Enhancement of ZnO light emission via coupling with localized surface plasmon of Ag island film

Enhancement of the light emission of ZnO films was observed by coupling through localized surface plasmons. By sputtering Ag islands onto ZnO films, their band gap emission coming through the Ag island films was enhanced by threefolds, while the defect emission was quenched. The enhancement was found to be mainly dependent on the sputtering time of the Ag islands, which is related to the island size. Furthermore, the relative spectral position between the ZnO emission band and the localized surface plasmon resonance bands of Ag islands was found to be decisive for the enhancement or quenching of photoluminescence, indicating that the emission intensity of ZnO films can be controlled by the Ag island size and the localized surface plasmon resonance band position.

Photoluminescence of Si-rich silicon nitride: Defect-related states and silicon nanoclusters

The photoluminescence (PL) from defect-related states and Si nanoclusters was observed in the Si-rich silicon nitride films simultaneously. The weaker red-light emission of Si nanoclusters was obtained in the 1100°C annealed films with the 514.5nm excitation. Due to the quantum confinement effect, the PL peaks redshift with the increase of the excess Si concentration. Excited by the 325nm line, strong PL from N and Si dangling bond centers was observed in either the as-deposited films or the 1100°C annealed ones. The results demonstrate that the luminescence from defect-related states or Si nanoclusters is selected by the excitation energy.

Electroluminescence of SnO2∕p-Si heterojunction

Polycrystalline SnO2 film of tetragonal rutile structure with an optical band gap of 3.9eV was formed by oxidation process at 1000°C on electron beam evaporation deposited Sn film. Room temperature electroluminescence from the SnO2∕p-Si heterojunction was observed at 590nm when the device was under sufficient forward bias with the positive voltage applied on the p-Si substrate. It is proposed that the electrons in the conduction band of SnO2 relax to defect states that resulted from the dangling bonds at the surface of the small SnO2 grains and then radiatively recombine with the holes in the valence band.

Correlation between luminescence and structural evolution of Si-rich silicon oxide film annealed at different temperatures

The visible red band light emission of the Si-rich silicon oxide films prepared by electron-beam evaporation with postannealing was investigated. The films annealed at temperatures lower than 600°C were composed of Si nanoclusters with high fraction of boundary atoms, featuring photoluminescence (PL) band centered at 700–710nm. By contrast, the PL bands of the films annealed at temperatures higher than 600°C redshifted with the expansion of the Si nanoclusters. The most intense light emission was observed in the 600°C annealed sample. The conversion of the luminescence mechanism from surface states controlled to quantum confinement controlled was proposed on the basis of the evolution of the film structure.

Photoluminescence of Tb3+ doped SiNx films grown by plasma-enhanced chemical vapor deposition

Room temperature photoluminescence (PL) properties of the Tb3+ ion implanted nonstoichiometric silicon nitride (Tb3+:SiNx) and silicon dioxide (Tb3+:SiOx) were studied. The films were deposited by plasma-enhanced chemical vapor deposition and then annealed at different temperatures for 1h in flowing N2 before or after the implantation. Results show that there are four intense PL peaks due to the intra-4f transitions of Tb3+ in the wavelength from 470to625nm for both kinds of films. Moreover, after postannealing at 1000°C, the integrated PL intensity of Tb3+:SiNx is much higher than that of Tb3+:SiOx. The energy transfer from the defect related energy levels to the Tb3+ ions will enhance the D45→Fk7 (k=3–6) luminescence of Tb3+ ions.