TEM investigations of epitaxial praseodymium oxide on silicon

We present results for epitaxial growth of praseodymium oxide as a potential high-K dielectric. From TEM (including high resolution electron microscopy and electron diffraction) we find that on Si(001) oriented surfaces, crystalline Pr₂O₃ grows in the Mn₂O₃ structure as (110)-domains, with two orthogonal in-plane orientations. On Si(111) we obtain epitaxial growth of Pr₂O₃ having the hexagonal La₂O₃ structure. These Pr₂O₃ layers can be overgrown epitaxially with silicon. We find that a phase transition takes place during the anneal of the as-grown films in N₂ at temperatures below growth temperature. Annealed films display again the cubic Mn₂O₃ structure, (111)-oriented but 180° rotated around the Si (111) surface normal.