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Mixed cation phases in sputter deposited HfO2–TiO2 nanolaminates

2008; American Institute of Physics; Volume: 93; Issue: 2 Linguagem: Inglês

10.1063/1.2957670

1520-8842

Massiel Cristina Cisneros-Morales, C. R. Aita,

Electronic and Structural Properties of Oxides

Nanolaminate HfO2–TiO2 films are grown by reactive sputter deposition on unheated fused SiO2, sequentially annealed at 573to973K, and studied by x-ray diffraction. A nanocrystalline structure of orthorhombic (o) HfTiO4 adjacent to an interface followed by monoclinic (m) Hf1−xTixO2 is identified. m-Hf1−xTixO2, a metastable phase, is isomorphous with m-HfO2 and a high pressure phase, m-HfTiO4. A Vegard’s law analysis shows that the Ti atomic fraction in m-Hf1−xTixO2 is much greater than Ti equilibrium solubility in m-HfO2. A space group-subgroup argument proposes that m-Hf1−xTixO2 arises from an o∕m-HfTiO4 second order phase transition to accommodate the larger Hf atom.