Beschreibung:
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We have investigated the compositional and structural properties of blue emitting BaAl<jats:sub>2</jats:sub>S<jats:sub>4</jats:sub>:Eu electroluminescent thin films fabricated by switching electron-beam evaporation using two targets. The use of X-ray photoelectron spectroscopy (XPS) revealed that the ratio of barium to sulfur in thin films is 1.0:2.0, which is identical to the stoichiometry of BaAl<jats:sub>2</jats:sub>S<jats:sub>4</jats:sub>. The X-ray diffraction (XRD) peaks from the thin film were assigned to those of a BaAl<jats:sub>2</jats:sub>S<jats:sub>4</jats:sub> crystal. The photoluminescence (PL) spectrum shows emission from the 4f<jats:sup>6</jats:sup>5d→4f<jats:sup>7</jats:sup> transition of the activated Eu<jats:sup>2+</jats:sup> ions in BaAl<jats:sub>2</jats:sub>S<jats:sub>4</jats:sub> crystals. These results indicate that the crystalline phase in thin films is only BaAl<jats:sub>2</jats:sub>S<jats:sub>4</jats:sub>. The thin films also contain a large amount of oxygen impurities, which result in the formation of an Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> layer and amorphous barium aluminate.
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