Substrate-suppressed phase transition in nano-crystalline thin films
Department of Materials and Interfaces, Weizmann
Institute of Science Rehovot, 76100, Israel
2 Department of Materials and Nuclear Engineering, University of Maryland College Park, MD, 20742, USA
Accepted: 16 September 2002
Upon substrate removal nano-crystalline cubic thin films transformed into the tetragonal phase. Randomly oriented nano-crystalline films were prepared with moderate residual tensile stress by sol-gel processing or RF sputtering. The low dielectric constant and the X-ray diffraction spectra identified the films as being cubic at room temperature. Despite the tensile stress in the substrate-supported films, the free-standing films became corrugated, indicating 0.3–0.5% lateral expansion. The fact that the cubic-to-tetragonal phase transition was responsible for the lateral expansion has been confirmed by a fivefold increase of the dielectric constant and a detectable piezoelectric effect.
PACS: 77.55.+f – Dielectric thin films / 77.22.Ch – Permittivity (dielectric function) / 77.80.Dj – Domain structure; hysteresis
© EDP Sciences, 2002