Studies On Preparation And Optical Properties Of The Undoped And Doped Li₂B₄O₇ Thin Films

Li₂B₄O₇ materials could store radiation information after being radiated. The energy is released by thermo-luminescence (TL) and optical stimulated luminescence (OSL) manners. The quantity of the energy is according to the tensity of the TL or the OSL. Moreover, the effective atomic number of the Li₂B₄O₇ material (Ze=7.26) is close to the body organizational tissue (Ze=7.13).Therefore, the material has application prospects in the intensity and the species of ray detection. Before the study of the TL and the OSL properties, it is necessary to study the luminescence properties of the Li₂B₄O₇ material. The methods of films'preparation in this work are the sol-gel method and the silk screen painting method. And the structural information of the films was obtained by the X-ray diffraction (XRD) analysis; we also studied the optical properties through optical absorption and photo- luminescence analysis. Furthermore we improved the film's optical properties by Cu and In elements doping .The experimental results showed that there were lots of impurity phase in films prepared by sol-gel method, therefore we have to improve the experimental technique in our later works. Because the melt point of the Li₂B₄O₇ material is very high , and it is not easy to decompose and oxidize under the high temperature. The films prepared by the silk screen painting method almost have no impurity phase even after the annealing under the high temperature and the thickness of the films could be controlled better.The Cu and In elements doping experimental results showed that the optical properties changed with the different doping concentration. The results also showed there were two absorption manners for Li₂B₄O₇:Cu ,In and Li₂B₄O₇:Cu films; the forbidden band gap of Li₂B₄O₇ thin films got smaller when they were doped with Cu and In element .These results would be favorable to the TL and OSL properties. The photo- luminescence results showed that slight doping could increase the luminescence intensity, but when the doping concentration is high there was center of luminescence quenching. When doped the Li₂B₄O₇: Cu films with In element at the same time, the luminescence intensity of the Li₂B₄O₇: Cu films reduced as the Cu concentration increased.