Chemical Solution Deposition of (Pb1−xCax)TiO3 Thin Films with x∼0.5 as New Dielectrics for Tunable Components and Dynamic Random Access Memories

Calcium lead titanate ((Pb,Ca)TiO 3 ) thin films, with calcium contents of ∼50 at.%, have been prepared by chemical solution deposition (CSD). Different synthetic sol-gel methods have been used for the preparation of the precursor solutions. 1,3-propanediol, OH(CH 2 ) 3 OH, and water, H 2 O, were used as solvents. Lead (II) acetate trihydrate, Pb(OCOCH 3 ) 2 .3H 2 O, and titanium di-isopropoxide bis(acetylacetonate), Ti(OC 3 H 7 ) 2 (CH 3 CO CHCOCH 3 ) 2 , were used as reagents of lead and titanium, respectively. Calcium was incorporated into the solutions as calcium acetate hydrate, Ca(OCOCH 3 ) 2 .xH 2 O, or as calcium acetylacetonate hydrate, Ca(CH3COCHCOCH3)2 .xH 3 O. Only the use of calcium acetate led to precipitate-free solutions. Pb(II)-Ti(IV)-Ca(II) sols were obtained when calcium acetate was refluxed with the lead and titanium reagents in a diol-water solvent. These sols led to films with a homogeneous compositional profile. Solutions obtained by mixing a water solution of calcium acetate with a Pb(II)-Ti(IV) sol led to films with a heterogeneous compositional profile in which an interface between the film and the Pt bottom electrode is formed. The films derived from the Pb(II)-Ti(IV)-Ca(II) sols have values of dielectric constant at room temperature of ∼500, which, together with their low leakage currents, low dielectric losses, and tunability, make these films promising for dynamic random access memories and tunable devices.