Study On Sol-gel Prepared Photoluminescence And Electroluminescence From Tb³⁺ Doped SiO₂ Thin Films

The Tb³⁺ doped SiO₂ photoluminescent films were prepared by using sol-gel method. The surface topography of the film was characterized by using Atomic Force Microscope (AFM). The excitation and emission spectra were measured by spectrophotometer equipment. The thickness of film was carried out by means of Elliptical Polarization Instrument. The layered optimization scheme was introduced. The thin film electroluminescent device of different concentration of Tb³⁺ was tried to be fabricated. In the TFEL, the pure SiO₂ was used as insulating layer and the Tb³⁺ doped SiO₂ film as luminescence layer.The luminescent feature was characterized by using self-made power source and the luminescent mechanism has been discussed.The Tb³⁺ doped SiO₂ luminescent films with green light emission were prepared by dip-coating method. The luminescent properties influenced by layer number of films have been studied. The thin films had very strong luminescent intensity, when the layer number was four and the thickness was about 400nm.The research showed that the luminescent intensity had close relationship with the surface topography of thin film and the internal structure of cluster.The Tb³⁺ doped SiO₂ luminescent films were also obtained by using spin coating method. The AFM pictures of the films indicated that there is no crackle on the surface of the films and the films are relatively uniform. The influences of concentration, the annealing temperature on the PL intensity of the films have been studied. When the doped ration of Tb³⁺ions was 0.5% and the annealing temperature was 750℃, the sample showed intense green emission. The analysis showed that the concentration quenching was caused by the exchange action between ions and the cross relaxation between energy level.Al³⁺ ions were added to the starting materials, the results showed that Al³⁺ can increase the PL intensity of Tb³⁺ ions. It may be due to the Al³⁺ ions involved in the network structure of SiO₂, which formed the function group of Si -O-Al that can resulted in the symmetry of coordination environment of the Tb³⁺ ions. The parity selection rules of field have been broaden by the 4f electronic configuration mixed with the opposite parity state, the transition of electric dipole moment from ⁵D₄ to ⁷F₅ have been strengthened.With layered optimization scheme, we tried to prepare thin film electrolumines-cent device of different concentration of Tb³⁺ by using sol-gel method. The device has been measured by using self-made power resource. The result showed that the device has optimum green emission, when the testing voltage was 150V and the frequency was 500HZ.