Heteroleptic Cyclopentadienyl-Amidinate Precursors for Atomic Layer Deposition (ALD) of Y, Pr, Gd, and Dy Oxide Thin Films

Thin films of rare-earth (RE) oxides (Y₂O₃, PrO_<i>x</i>, Gd₂O₃, and Dy₂O₃) were deposited by atomic layer deposition from liquid heteroleptic RE­(<i>ⁱ</i>PrCp)₂(<i>ⁱ</i>Pr-amd) precursors with either water or ozone as the oxygen source. Film thickness, crystallinity, morphology, and composition were studied. Saturation was achieved with Gd₂O₃ when O₃ was used as the oxygen source at 225 °C and with Y₂O₃ with both oxygen sources at as high temperature as 350 °C. The growth rates were 0.90–1.3 Å/cycle for these processes. PrO_<i>x</i> was challenging to deposit with both oxygen sources but with long, 20 s purges after the water pulses uniform films could be deposited. However, saturation was not achieved. With Dy₂O₃, uniform films could be deposited and the Dy­(<i>ⁱ</i>PrCp)₂(<i>ⁱ</i>Pr-amd)/O₃ process was close to saturation at 300 °C. The different oxygen sources had an effect on the crystallinity and impurity contents of the films in all the studied processes. Whether ozone or water was better choice for oxygen source depended on the metal oxide material that was deposited