An X-ray photoelectron spectroscopy study of BaAl 2S 4 thin films

Abstract

Depth profiling with X-ray photoelectron spectroscopy (XPS) was used to study BaAl 2S 4:Eu thin films, which were prepared as a multi-layered stack of electron beam deposited BaS:Eu and Al 2S 3 thin films. A post-deposition thermal annealing at 900 °C was performed to obtain full reaction towards BaAl 2S 4:Eu. Depth profiles were recorded for both as-deposited and annealed thin films. The influence of exposure to ambient air prior to and after ex situ annealing on the composition of the films is discussed. XPS photoline positions and shapes are interpreted to understand the formation and degradation of BaAl 2S 4:Eu. Such information is highly important for the optimisation of BaAl 2S 4:Eu thin films as the blue emitter in inorganic thin film electroluminescent displays.