The c-axis length and phase transition temperature change in an epitaxial PbTiO3thin film grown on a SrTiO3(001) substrate by metal-organic chemical vapour deposition

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Abstract
The room-temperature and high-temperature theta -2 theta X-ray diffraction patterns of the PbTiO3 thin films grown on SrTiO3(001) substrates by metal-organic chemical vapour deposition under reduced pressure show that the epitaxial PbTiO3 thin film has a smaller c-axis length and a higher phase transition temperature than does the bulk material. The coexistence of a and c domains has also been found through the changing temperature X-ray diffraction pattern of the as-grown film. Taking the additional strain items into consideration the original Landau-Ginzburg-Devonshire form of the elastic Gibbs free energy of the PbTiO3 thin film is different from that of the bulk material, upon this, a relationship between the phase transition temperature and c-axis strain in the epitaxial film has been proposed. The reason for the c-axis length shortening has been discussed.