Photoluminescence and Stoichiometry Correlation in Nanocrystalline EuO<i>_x</i> Thin Films: Tunable Color Emission

Abstract

The development of broadband and ultracompact optoelectronic devices relies on the possibility of fabricating bright and tunable emitters at the nanoscale. Here, we show emission from EuO <i>_x</i> (1 ≤ <i>x</i> < 1.4) thin films on silicon formed by nanocrystals with average sizes in the range of 5 nm. The photoluminescence emission of the nano-EuO <i>_x</i> films is tunable as a function of the oxygen concentration changing from a green broadband Eu²⁺-related emission to a narrow red Eu³⁺-related emission. To reach these results has been instrumental through the use of a new methodology specially designed to achieve high-quality europium oxide films whose compositional properties are controlled by the growth base pressure and preserved thanks to a chemically stable and transparent cover layer of Al₂O₃. Our findings confirm the outstanding potential of nanostructured EuO <i>_x</i> films as "one-compound" optical elements with tunable emission properties for their implementation in integrated silicon-based devices.