Fabrication Of SiN_x:Tb³⁺ Thin Film And Its Coupling With Silver Mediated Surface Plasmon Polaritons

Due to its energy savings and environmental benefits, high efficiency of solid-state light source has stimulated great interests. There are two approaches employed to attain this aim: suppression of nonradiative recombination processes or decreasing the radiative emission decay time. Surface plasmon polaritons (SPP), which are electromagnetic waves that propagate along the interface between vacuum or material with a positive dielectric constant and metal, has been experimental achieved in increasing the quantum efficiency of organic light emitting diode, InGaN/GaN quantum well, pn junction. Hence, in this thesis SPP was employed to acquire a high quantum efficiency of SiN_x:Tb³⁺, which can be integrated into silicon chips for tiny light sources. The main results achieved are listed as following:A non-stoichiometric silicon nitride (SiN_x) film was deposited by plasma enhanced chemical vapor deposition (PECVD). The ratio of NH₃/SiH₄ flows was varied from 1 to 15 to get different Si concentrations in the films. The experiment indicates that the band-gap of silicon nitride thin film will increase with the increase of the flow ratio of NH₃/SiH₄. With the increase of anneal temperature, the Fourier transform infrared (FTIR) spectrometer show that the peak of Si-N bond is blue shifted with litter intensity changeable, while the peak intensities of Si-H bond at 2100cm^-1 and N-H band at 3350cm^-1 all decreased. It is the escaping of large mount of hydrogen from the films during annealing that resulted in the above phenomena.The Tb³⁺ ions were implanted into the SiN_x films. Strong and sharp PL peak of Tb³⁺ ions were observed at about 543 run at all SiN_x films grown with different flow ratio of NH₃/SiH₄. Howerver, partly due to the silicon nanocrystals precipitated from the matrix after annealing at high temperature, the PL intensity of the Tb³⁺ is decreased.The time resolved photoluminescence (TRPL) at room temperature show that the emission decay time is 708μs corresponded to PL peak at 543 nm. After sputtering silver films, the emission decay time of Tb³⁺ ions decreased, irrespectively of the size of Ag islands. However, due to the increased size of Ag islands after rapid thermal processing (RTP), emission decay time was increased comparing to samples with silver film as deposited. Assuming the emitter to be a damped oscillating electric dipole, the experimental results are predicted coincidently with the classical CPS theory, which indicated that the internal quantum efficiency of the SiN_x:Tb³⁺ was improved by the silver island film.By introducing filler layers, the effect of the distance on coupling between SPP and SiN_x:Tb³⁺ was investigated. It is found that when the emitter located at the in-phase of the electric field of the SPP, the emission decay time reached its maximum, while at the reversed-phase of the SPP, the emission decay time reached its minimum.To avoid been absorbed by silver before exciting the SiN_x:Tb³⁺ film, the emitter was fabrication on quartz substrate. Since the substrate become transparent, not only the emission decay time becomes decreased, but also the increase of the PL intensity becomes possible. And it was found that variety of the thickness of silver island films resulted in different intensity of PL of Tb³⁺. The enhancement of PL was observed when the sputter time exceeds 100s, since more energy was absorbed to excited SPP. On the other hand, due to the coupling between nanocrystal or defect and SPP, the existence of nanocrystal or defect in SiNx film would decrease the coupling efficiency between SiN_x:Tb³⁺ and SPP.