rf Sputtered Luminescent Rare-Earth Oxysulfide Films

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Abstract
Thin luminescent films of lanthanum and gadolinium oxysulfide (RE2O2S) were prepared by radio-frequency sputtering in an Ar–H2S mixture. Small additions of Eu, Tb, or Tm produced red, green, or blue emissions, respectively. A luminance of 40 000 ftL from a La2O2S:Tb film was observed. The composition of the sputtered films was found to be very dependent upon the H2S pressure in the sputtering chamber. The film composition as a function of H2S pressure was determined and described. In order to achieve maximum luminescence, the films were treated in an H2–SO2 atmosphere at 1000 °C, and x-ray diffraction and luminous emission linewidths were observed to have decreased after treatment. Crystalline growth within the film and improved oxygen sulfur stoichiometry resulting from the treatment process are believed to be primarily responsible for the increase in luminous efficiency. The maximum luminous efficiency of the films was measured to be approximately 1/10 that of corresponding powder screens. Attempts to increase the film luminance by reducing the internal trapping of the radiation are discussed.

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