Thickness driven stabilization of saw-tooth like domains upon phase transitions in ferroelectric thin films with depletion charges
Mısırlıoğlu, Burç and Çöloğlu, Hale Nur and Yıldız, Mehmet (2011) Thickness driven stabilization of saw-tooth like domains upon phase transitions in ferroelectric thin films with depletion charges. (Submitted)
Ionized impurities have nearly always been neglected in discussing the limit of functionality of ferroelectric thin films. One would certainly expect that the thickness limit for functionality would be altered in the presence of ionized impurities but how this would occur remains unclear. In this article, we analyze the domain structures as well as the phase transition temperatures in films with depletion charges for various film thicknesses. Due to the inhomogeneity created by depletion charges, saw-tooth like domain structures develop spanning the entire film thickness that are possible in films with depletion charges having perfect electrode screening, i. e., ideal electrodes if the film is above a critical thickness. On the other hand, the phase transition of the ultrathin structures with dead layers is always into the multidomain state during cooling from the paraelectric state regardless of the presence of depletion charges. Transition temperature in films with dead layers does not depend nearly at all on the depletion charge density unless it is very high (>1026 ionized impurities/m3). Relatively thick films (>8 nm in this work) with dead layers that have very high depletion charge densities have transition temperatures very similar to those with the same charge density but with ideal electrodes, making us conclude that thick films with high depletion charge densities will hardly feel the dead layer effects. The results are provided for (001) BaTiO3 films grown on (001) SrTiO3 substrates with pseudomorphic top and bottom metallic electrodes.
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