Traditionally, simple and volatile metal compounds, such as halides, alkoxides, and β-diketonates, have been used to grow oxide films by ALD.¹ However, these precursors exhibit a number of shortcomings such as low reactivity towards O sources as well as introducing Cl or C impurities into the films.To avoid these and other potential difficulties, it is necessary to explore and develop new precursor chemistry.

In recent years, cyclopentadienyl (Cp)-compounds and amido complexes have emerged as ALD precursors.² Among these, we recently reported novel Cp-compounds to grow HfO₂ at high temperatures of 350-500°C.³ Additionally, the ALD of Ga₂O₃ and Er₂O₃ using dialkylamido-based and amidinate-containing precursors, respectively, is discussed.^4,5 Based on this, the growth of Er_xGa_2-xO₃ is demonstrated from 2 systems, the first one using β-diketonates and O₃ while the 2nd one uses Er(CpMe)₃, Ga₂(NMe₂)₆ and H₂O.⁶ Finally, we have an example of a dialkylamido-based dimer for oxidation state control in W oxide films, where the reaction between W₂(NMe₂)₆ and H₂O maintains W in its +3 state producing W₂O₃.⁷

Ta₂O₅ and BaTiO₃ are important materials for microelectronics. Discovery of new ALD precursors could prove useful for these materials, especially for Ba, which lacks stable sources. The new pyrazolate-based precursor for Ta exhibits high thermal stability and produces films of low impurity levels, whereas the novel pyrazolyl-based Ba precursor shows promise towards developing a feasible ALD process for BaTiO₃.^8,9

1. L. Niinistö et al. Phys. Stat. Solidi a 201 (2004) 1443.
2. M. Putkonen and L. Niinistö, Top. Organomet. Chem. 9 (2005) 125.
3. J. Niinistö et al. Chem. Mater. 19 (2007). In press.
4. C.L. Dezelah IV et al. Chem. Mater. 18 (2006) 471.
5. J. Päiväsaari et al. J. Mater. Chem. 15 (2005) 4224.
6. C.L. Dezelah IV et al. Ibid. 17 (2007) 1308.
7. C.L. Dezelah IV et al. J. Am. Chem. Soc. 128 (2006) 9638.
8. C.L. Dezelah IV et al. Ibid. (2007). Submitted.
9. C.L. Dezelah IV et al. To be published.

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