Lanthanide fluoride thin films have gained interest as materials for various optical applications, including electroluminescent displays and mid-IR lasers. However, the number of atomic layer deposition (ALD) processes for lanthanide fluorides has remained low. In this work, we present an ALD process for TbF3 using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)terbium and TiF4 as precursors. The films were grown at 175–350 °C. The process yields weakly crystalline films at the lowest deposition temperature, whereas strongly crystalline, orthorhombic TbF3 films are obtained at higher temperatures. The films deposited at 275–350 °C are exceptionally pure, with low contents of C, O, and H, and the content of titanium is below the detection limit (<0.1 at. %) of time-of-flight elastic recoil detection analysis (ToF-ERDA). Due to the lack of titanium impurities, the films show high transmittance down to short UV wavelengths.
Atomic layer deposition of TbF3 thin films
Elisa Atosuo, Juha Ojala, Mikko J. Heikkilä, Miika Mattinen, Kenichiro Mizohata, Jyrki Räisänen, Markku Leskelä, Mikko Ritala; Atomic layer deposition of TbF3 thin films. J. Vac. Sci. Technol. A 1 March 2021; 39 (2): 022404. https://doi.org/10.1116/6.0000790
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