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  • Kukli, Kaupo; Kemell, Marianna; Castan, Helena; Duenas, Salvador; Seemen, Helina; Rähn, Mihkel; Link, Joosep; Stern, Raivo; Ritala, Mikko; Leskelä, Markku (2018)
    Nanocrystalline HfO2:Al2O3 mixture films and nanolaminates were grown by atomic layer deposition at 350 degrees C from metal chloride precursors and water. Formation of metastable HfO2 polymorphs versus monoclinic phase was affected by the relative amount and thickness of constituent oxide layers. The films exhibited saturative magnetization and charge polarization in externally applied fields at room temperature. The films also demonstrated resistive switching behavior with considerable window between low and high resistance states. (C) The Author(s) 2018. Published by ECS.
  • Seppälä, Sanni; Niinistö, Jaakko; Mattinen, Miika; Mizohata, Kenichiro; Räisänen, Jyrki; Noh, Wontae; Ritala, Mikko; Leskelä, Markku (2018)
    La2O3 thin films were deposited by atomic layer deposition from a liquid heteroleptic La precursor, La(iPrCp)2(iPr-amd), with either water, ozone, ethanol, or both water and ozone (separated by a purge) as the oxygen source. The effect of the oxygen source on the film growth rate and properties such as crystallinity and impurities was studied. Saturation of the growth rate was achieved at 225 °C with O3 as the oxygen source. With water, very long purge times were used due to the hygroscopicity of La2O3 but saturation of the growth rate was not achieved. Interestingly, when an O3 pulse was added after the water pulse with a purge in between, the growth rate decreased and the growth saturated at 200 °C. With ethanol lanthanum hydroxide was formed instead of La2O3 at 200–275 °C whereas hexagonal La2O3 films were obtained at 300 °C but the growth was not saturative. Using the separate pulses of water and ozone in the same deposition provided the best results from the four studied deposition processes. After annealing the films deposited with the La(iPrCp)2(iPrAMD)/H2O/O3 process showed pure hexagonal phase in all the films regardless of the deposition temperature, whereas mixtures of cubic and hexagonal La2O3 were seen with the other processes.