Tuning Eu3+ emission in europium sesquioxide films by changing the crystalline phase

Abstract We report the growth of europium sesquioxide (Eu 2 O 3 ) thin films by pulsed laser deposition (PLD) in vacuum at room temperature from a pure Eu 2 O 3 ceramic bulk target. The films were deposited in different configurations formed by adding capping and/or buffer layers of amorphous aluminum oxide (a-Al 2 O 3 ). The optical properties, refractive index and extinction coefficient of the as deposited Eu 2 O 3 layers were obtained. X-ray photoelectron spectroscopy (XPS) measurements were done to assess its chemical composition. Post-deposition annealing was performed at 500 °C and 850 °C in air in order to achieve the formation of crystalline films and to accomplish photoluminescence emission. According to the analysis of X-ray diffraction (XRD) spectra, cubic and monoclinic phases were formed. It is found that the relative amount of the phases is related to the different film configurations, showing that the control over the crystallization phase can be realized by adequately designing the structures. All the films showed photoluminescence emission peaks (under excitation at 355 nm) that are attributed to the intra 4f-transitions of Eu 3+ ions. The emission spectral shape depends on the crystalline phase of the Eu 2 O 3 layer. Specifically, changes in the hypersensitive 5 D 0  →  7 F 2 emission confirm the strong influence of the crystal field effect on the Eu 3+ energy levels.