Nanocrystalline Oxide-Based Luminiscent Nanophotonic Structures

Abstract

Light nanoemiters are the cornerstone of photonic integrated applications including displays for consumer products such as phones and smartwatches, and for advanced application such as quantum emitters. In this context it is appealing to have access to a single material platform suitable for tunable wavelength emission, and if possible, that can provide broadband white light emission. Solid state light emitting nanostructures based on Europium ions are a promising solution. When imbedded in a solid they can have two oxidation states Eu3+ or Eu2+ which upon excitation show a either a high purity red emission (associated to the Eu3+ dipole-forbidden intra-4f shell 5D0® 7F2 transition), or a broad emission band in the 450- 600 nm spectral region (related to the Eu2+ dipole-allowed 4f6 5d -> 4f7 transitions). Here I will discuss the strategy that our group is following based on europium oxides EuOx, 1/3<x<1, as this approach allows to have a high density of emitters. Moreover, their electric and optical properties can be tuned from the sesquioxide Eu2O3 that is a wide bandgap dielectric that shows the Eu3+ ion related narrow band red emission, to the monoxide EuO that is a semiconductor that shows a wide band white light emission related to the Eu2+ ion. For the nanoemitters we have prepared EuOx nanocrystalline films with high transparency, and in which the coexistence of both oxidation Eu states enables wavelength tunability [1.2]. Finally, recently we have designed 2D hybrid nanoemitters by integrating the EuOx films with metallic metasurfaces in order to induce an enhancement of the emission intensity by selective plasmonic excitation [3].