Electroluminescence from CaS:TmF3 film prepared by radio frequency magnetron sputtering

Blue electroluminescence is reported from CaS:TmF3 thin films prepared by radio frequency magnetron sputtering method. The dependences of brightness on substrate temperature, concentration of TmF3, and the applied voltage were investigated on alternating current thin-film electroluminescent devices. The obtained maximum brightness was above the level of ZnS:TmF3 devices. The equivalent average energy of the excited electrons contributed to the electroluminescence in CaS:TmF3 alternating current thin-film electroluminescent devices and was estimated at around 4.23 eV by comparing the ratio of infrared to blue peak in electroluminescent spectra with that in photoluminescent spectra excited by different photon energy. The excitation processes of electroluminescence in CaS:TmF3 thin films were assumed to be energy transfers from the conduction band edge to Tm3+ centers. (C) 1998 American Institute of Physics.