Lanthanum Oxyfluoride Sol−gel Thin Films by a Simple Single-Source Precursor Route

Highly transparent and homogeneous nanostructured LaO1-xF1+2x (0≤ x ≤ 1) thin films have been synthesized by a simple sol−gel procedure using La(hfa)3·diglyme (Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme = bis(2-metoxyethyl) ether) as source compound for both lanthanum and fluorine. While thermal treatments up to 500 °C resulted in highly fluorinated nanosystems, i.e., LaF3 at 300 °C and LaF3 + LaOF at 500 °C, pure and single-phase nanostructured lanthanum oxyfluoride thin films with a mean crystallite size of ∼15 nm have been obtained at 700 °C. The microstructure and composition of the samples and their interplay with the synthesis procedure were investigated by glancing incidence X-ray diffraction, X-ray photoelectron, and X-ray excited Auger electron spectroscopy. Finally, the optical properties of the films were studied by UV−vis−NIR spectroscopy and spectroscopic ellipsometry.