On the effects of stresses in ferroelectric (Pb,Ca)TiO3 thin films

Grazing angle X-ray diffraction, profilemetry, permittivity vs. temperature end Raman spectrometry measurements have been carried out on Ca-substituted lead titanate thin films prepared by sol-gel and deposited on Pt/TiO2/SiO2/(100)Si substrates. Films with thicknesses of 150 and 350 nm were obtained. The crystalline (Pb,Ca)TiO3 films were randomly oriented with a and c parameters slightly different from those of bulk ceramics. Profilemetry measurements indicated that the films were under tensile stresses, developed during the drying of the deposited wet layer and during the thermal treatment of crystallization of the amorphous film. These stresses were confirmed by the shift obtained in the Raman frequencies of these films. As a consequence of these stresses, a positive shift of the maximum of the permittivity vs. temperature is measured. (C) 1998 Elsevier Science S.A.