Phys. Rev. Lett. 94, 047603 (2005) [4 pages]Ferroelectricity and Tetragonality in Ultrathin PbTiO3 FilmsReceived 17 December 2003; published 3 February 2005 The evolution of tetragonality with thickness has been probed in epitaxial c-axis oriented PbTiO3 films with thicknesses ranging from 500 down to 24 Å. High resolution x ray pointed out a systematic decrease of the c-axis lattice parameter with decreasing film thickness below 200 Å. 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 Å display a significantly reduced polarization but still remain ferroelectric. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.047603
DOI:
10.1103/PhysRevLett.94.047603
PACS:
77.80.–e, 31.15.Ar, 68.55.Jk, 77.84.Dy
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