Luminescent thin films of Eu-bearing UiO-66 Metal Organic Framework prepared by ALD/MLD

Abstract Crystalline Eu3+-2-aminoterephthalic acid thin (ca. 22 µm) films have been prepared by Atomic/Molecular Layer Deposition (ALD/MLD) on Si/SiO2 substrates. The β-diketonate complex precursor europium(III)-tris-(2,2,6,6-tetramethyl-3,5-heptanedionate, Eu(thd)3, was reacted with 2-aminoterephthalic acid, NH2TA. X-ray diffraction indicates the films deposited at 180°C exhibit the structure of UiO-66, a Zr-bearing metal organic framework. Scanning electron microscopy and atomic force microscopy show that the prepared films are very smooth and uniform, essentially defect-free, with a surface topography comprising evenly distributed hills without sharp edges, well adherent to the substrate. Attenuated total reflectance fourier transform infrared witnesses the presence of the organic ligand in the film and its coordination to the metal. X-ray photoelectron spectroscopy confirms the trivalent Eu oxidation state. Due to their thermal stability, fair volatility and facile synthesis, β-diketonate complexes have been shown to be suitable ALD precursors for preparing high-quality lanthanide organic framework thin films, enabling a single-step gas phase method for the synthesis of luminescent films.