Preparation, analyze and pure blue-emitting electroluminescent devices for Tm ion doped rare-earth oxysulfide thin films evapolated by reactive deposition

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Although rare-earth (Y,La, etc) oxide and oxysulfide show efficient luminescence excited with cathode ray and ultraviolet light, there are only a few reports on studies of electro-luminescent devices used these materials, because of difficulty for high quality films.In this study, the growth technique for Tm^<3+> ion doped rare-earth oxysulfide thin films (Y_2O_2 : Tm, La_2O_2S : Tm) having stoichiometric composition are developed in order to obtain the pure blue-emitting electroluminesent device.The following results were obtained.(1) The coprecipitation method is suitable for the prepareation method of the oxide-fluorescent powder which is used as the starting material for the evaporation.In the case of the oxysulfide-fluorescent powder, it is the suitable technique that sulfur is added in the oxide-fluorescent podwer and fired (sulfuration) .(2) Oxide-fluorescent thin-films having good crystallinity were obtained.(3) Oxysulfide-fluorescent thin-films having good crystallinity were also obtained by reactive deposition of the oxide-fluorescent powder and the sulfur.(4) Rare-earth oxide and rare-earth oxysulfide thin-film electroluminescent devices which have stacked structure of the emission layrs and semicoductor layrs show blue emission.(5) The excitation mechanism of the emission center was discussed in order to improve the luminance of electroluminescent device.