Processing and characterization of compositionally modified PbTiO₃ thin films prepared by pulsed laser deposition

Abstract

Modified lead titanate of 0.9PbTiO3 −0.1Pb(Mg0.5 W0.5)O3 thin films have been deposited onto Pt-coated Si substrates by pulsed laser deposition. Films were crystallized in situ during deposition or by post-depositional heat treatment (post-annealing). Compositional and structural characterization showed that the phase formation and microstructure of the films were highly sensitive to deposition conditions. Perovskite single phase films were formed in situ at 650 °C, PO2 = 40 Pa as well as by post-annealing amorphous films at 650 °C. In the post-annealing process, the amorphous as-deposited phase was crystallized to perovskite and/or pyrochlore, and the ratio of perovskite to pyrochlore was found to be influenced by the depositional PO2. Depending on the deposition temperature, the grain structures of the crystallized films were columnar or equiaxed. A relatively homogeneous surface morphology was obtained by deposition at a lower pressure (PO2 = 13 Pa). The in situ crystallized films showed variable crystallographic orientation. The more (111) oriented films had the lowest remanent polarizations and the highest coercive fields. A method for preparing randomly oriented films, via a two-step deposition process with intermediate annealing, is believed to give the most consistent results and the best ferroelectric properties at the present level of development.

Deposition of PbTiO3 films on Pt/Si substrates using pulsed laser deposition

“…Lee et al have also reported a similar reduction in the tetragonality of films as compared to the bulk target, in compositionally modified lead titanate thin films. 9 The degree of preferred orientation in a film can be represented by a definition proposed by Lotgering 26 which is as …”

“…Perhaps for this reason there are a larger number of reports on doped PbTiO 3 (e.g. La:PbTiO 3 ), [8][9][10][11][12] in which the spontaneous strain is much reduced. The difficulty of the spontaneous strain is avoided by the use of targetless preparation techniques such as solution deposition.…”