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Abstract

STM imaging and cathodoluminescence spectroscopy are used to explore the morphology and optical properties of Eu₂O₃ nano-islands grown on MgO(001) thin films. The global emission properties are governed by intense photon peaks at around 600 nm, arising from forced-dipole transitions in the 4f-state manifold of Eu³⁺ ions placed in a non-centrosymmetric crystal field. Local optical spectra obtained in the tunneling mode of the STM reveal that the Eu₂O₃ islands are responsible for the distinct optical response and not isolated Eu³⁺ ions inside the MgO matrix. Our work demonstrates that thin-film model systems can be used to elucidate fundamental properties of Eu-containing phosphors on the nanometer scale.