title: Ferroelectricity and tetragonality in ultrathin PbTiO3 films.
abstract: The evolution of tetragonality with thickness has been probed in epitaxial c-axis oriented PbTiO3 films with thicknesses ranging from 500 down to 24 A. High resolution x ray pointed out a systematic decrease of the c-axis lattice parameter with decreasing film thickness below 200 A. Using a first-principles model Hamiltonian approach, the decrease in tetragonality is related to a reduction of the polarization attributed to the presence of a residual unscreened depolarizing field. It is shown that films below 50 A display a significantly reduced polarization but still remain ferroelectric.
authors.affiliation: DPMC, Université de Genéve, 24 Quai Ernest-Ansermet, CH-1211 Genéve 4, Switzerland. Celine.Lichtensteiger@physics.unige.ch
authors.forename: Céline
authors.initials: C
authors.lastname: Lichtensteiger
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Triscone
authors.forename: Javier
authors.initials: J
authors.lastname: Junquera
authors.forename: Philippe
authors.initials: P
authors.lastname: Ghosez