Exploring OH incorporation pathways in pulsed laser deposited EuOOH thin films

Abstract

This study sheds light on the formation of EuOOH thin films intended for photonic applications in light emission. To this end, we designed a unique experiment in which we deposited films by pulsed laser deposition from an Eu2O3 target followed by low temperature annealing in an isotopic furnace, which allows selecting atmospheres (18O2 or D218O vapour) containing specific isotopes. Ion beam techniques have been used for the absolute determination of 16O and H content as well as that of the isotopes (18O, D) incorporated in the films upon annealing. A large content of either H2O or hydroxyl (OH−) groups was identified in the as-deposited films by infrared spectroscopy, while the incorporation of 18O or D upon annealing is limited (≤8 % and ≤ 4 %, respectively). Yet, annealing is a critical and necessary step to achieve the right stoichiometry and to induce the formation of hydroxides. Films produced under the optimum deposition pressure range (≤4 × 10−4 Pa) and annealing atmosphere (D218O) show the EuOOH monoclinic structure, while their photoluminescence response is in excellent agreement with the emission of Eu3+ ions in monoclinic EuOOH.