General rule for the determination of c-axis orientation of Pb-based tetragonal ferroelectric oxide film prepared by CVD

Abstract

fhin films of Pb-based tetragonal ferroelectric materials, such as Pb(Zr, Ti)O3 and (Pb, La) (Zr, Ti)O3, have been recognized to have wide application as electronic devices because of their excellent properties. The properties of these materials are widely known to depend on their crystal orientation, especially the degree of c-axis orientation [1]. Therefore the control of orientation is very important when attempting to realize reproducible preparation of film with high performance. Until now, the degree of c-axis orientation of these films has been reported to be affected by the cooling rate after deposition [2-5], the thermal expansion coefficient of the substrate [6] and the composition of the film [7]. However, an overall mechanism has not been proposed. In a previous study [8], it was concluded for Pb(Zr, Ti)O3 film prepared by chemical vapour deposition (CVD) that the degree of c-axis orientation depended on the thermal strain parallel to the surface of the substrate under the cooling process from the deposition temperature to the Curie temperature. This thermal strain, e, is expressed as follows [9]: