Preparation and characterization of Pb(Nb,Ti)O3 thin films by metalorganic chemical vapor deposition

Abstract

Lead niobium titanate, Pb(Nb,Ti)O3, thin films were prepared on various substrates by metalorganic chemical vapor deposition from the Pb(C11H19O2)2–Nb(O⋅C2H5)5–Ti(O⋅i-C3H7)4–O2 system. Polycrystalline films with (111) orientation and epitaxially grown films with c-axis orientation were deposited on the (111)Pt/Ti/SiO2(100)Si and PbTiO3/(111)Pt/Ti/SiO2/(100)Si substrates, and (100)SrRuO3//(100)LaAlO3 substrate, respectively, at 620 °C. Nb content in the film can be controlled only by changing the input gas flow rate of Nb(O⋅C2H5)5 under the excess gas flow rate of Pb(C11H19O2)2. The composition of the film was independent of the deposition temperature from 400 to 620 °C. The single phase of Pb(Nb,Ti)O3 was deposited up to the Nb content of about 5 at % and pyrochlore phase was codeposited above this Nb content. Leakage current density decreased with the increasing Nb content in the film up to 6.5 at %. Coercive field (Ec) of the film was about 130 kV/cm and was independent of the Nb content and the kinds of substrates. On the other hand, the remanent polarization (Pr) of the film on the (111)Pt/Ti/SiO2/(100)Si substrate increased from 9 to 29 μC/cm2 with the increasing Nb content from 2.1 to 4.8 at %. Pr of the film on the (100)SrRuO3//(100)LaAlO3 substrate was smaller than those of the (111)Pt/Ti/SiO2/Si and PbTiO3/(111)Pt/Ti/SiO2/Si substrates.