Nanostructured CaF₂:Ln³⁺ (Ln³⁺ = Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺) Thin Films: MOCVD Fabrication and Their Upconversion Properties

Abstract

Calcium fluoride represents one of the most efficient hosts for up‐conversion or down‐conversion emissions. A simple metal organic chemical vapor deposition approach is applied to the fabrication of CaF 2 nanostructured thin films using the fluorinated “second‐generation” β‐diketonate compound Ca(hfa) 2 •diglyme•H 2 O as a Ca‐F single‐source precursor. The versatility of the process is demonstrated for the fabrication of up‐converting Yb/Er or Yb/Tm codoped CaF 2 films on Si, quartz, and glass substrates. The Ln(hfa) 3 •diglyme (Ln = Tm, Er, Yb) precursors are used as sources of the doping ions. Structural, morphological, and compositional characterization of the films shows the formation of polycrystalline CaF 2 films with a very uniform surface and suitable doping. In fact, an appropriate tuning of the mixture composition, i.e., the Ca:Ln ratio in the multicomponent source, permits the deposition of films with the desired stoichiometry. The films show promising up‐conversion properties in the visible and near infrared regions upon laser excitation for both doping mixtures.