Phase structure of epitaxial Pb(Zr,Ti)O3 thin films on Nb-doped SrTiO3 substrates

Epitaxial Pb(Zr,Ti)O3 (PZT) films were deposited on Nb-doped SrTiO3 (Nb:STO) monocrystalline wafers by a sol-gel method. It was observed that phase structure of prepared films depends on the orientation of Nb:STO substrates. Interestingly, tetragonal structure was only found for [001]-oriented PZT film on Nb:STO(100) substrate, whereas Nb:STO(111) substrate resulted in a [111]-oriented rhombohedral PZT film, regardless of Zr∕Ti ratios ranging from 40∕60 to 60∕40. The influence of substrate orientation on phase structure of epitaxial PZT films was discussed on basis of the lattice matching. Ferroelectric and piezoelectric properties of PZT films on different Nb:STO substrates were also studied.