Research and analysis on the thin films sputtered by the Ba-Al-S:Eu target fabricated by powder sintering

Abstract

Europium-doped barium thioaluminate (BaAl 2 S 4 :Eu) is currently the most efficient blue phosphor for inorganic thin film electroluminescent (iEL) device. To produce the full-color EL device, several kinds of blue-emitting layer were attempted and tested. As a key point of blue-emitting layer fabrication, single target sputtering deposition is an effective method. In this work, new structural target is introduced and the fabricated process is expatiated. The PL spectra of asfabricated targets show that both of two, 3mol% and 5mol% europium-doped, have blue emitting property. According to the PL spectra excited by 290nm, 300nm and 320nm ultraviolet, emission peaks located in the region near 470nm. So the as-fabricated targets can be used in single target sputtering deposition on thin film of BaAl 2 S 4 :Eu. XRD pattern indicates that there are 4 different phases, barium tetraaluminum sulfide (BaAl 4 S 7 ), barium sulfide (BaS), europium sulfide (EuS) and barium aluminum oxide (BaAl 2 O 4 ), in target 1. Besides these four compounds, other two phases, aluminum sulfide (Al 2 S 3 ) and barium thioaluminate (BaAl 2 S 4 ), are detected in target 2. Considering the analysis results, especially the hydrolyzation of Al 2 S 3 , target 1 is more suitable for sputtering deposition of BaAl 2 S 4 :Eu thin film. XPS and X-ray Fluorescence patterns describe the precise molar ratio of each element. In target 1 the relative atom concentration of barium, aluminum, sulfur and oxygen can be calculated from the pattern and molar ratio is about 9:33:41:17. Molar ratio of barium and europium is about 1:0.03. In short, the barium thioaluminate doped by europium sputtering target 1 is better to be applied in the fabrication of blue-emitting layer in inorganic electro-luminescent devices.