Epitaxially induced high temperature (> 900 K) cubic-tetragonal structural phase transition in BaTiO3 thin films

For (001)(c) oriented BaTiO3 thin films, it has been found that epitaxial constraint can result in a dramatic increase in the temperature of a tetragonal (T) structural phase transition. For 2000-Angstrom-thick films grown directly on SrTiO3 substrates, a T-->cubic (C) phase transition was found on heating at >950 K, where the lattice constant changed smoothly with temperature. It was also found for films of the same thickness that the T-->C transition is nearly restored to that of bulk crystals by the use of a buffer layer, which relaxes the epitaxial constraint. These results provide evidence of an epitaxially induced high temperature structural phase transition in BaTiO3 thin films, where the ferroelectric (internal) and structural (external) aspects of the phase transition are decoupled. (C) 2004 American Institute of Physics.