Towards high performing ferroelectric thin films

Abstract

The contribution concerns various processing issues of ferroelectric thin films made by chemical solution deposition. The first part is related to PZT thin films prepared by 2-methoxy-etanol route on Silicon substrate. A careful molecular design of Pb(Zr,Ti)O3 (PZT) precursor solution enables to lower processing temperature of titanium rich films (PZT 30/70) down to 400oC and the composition close to morphotropic phase boundary (PZT 50/50) to 500oC The dielectric properties of the films are well compared to those crystallized at 650¿700oC. Clear correlation between enhanced dielectric properties and improved chemical homogeneity provided by precursor structure is demonstrated. The dielectric permittivity 1500 of PZT 50/50 makes these films attractive for capacitor application. The second part relates the processing issues and dielectric properties of (Ba,Sr)TiO3 (BST 30/70) thin films. Films are processed by 2-methoxy-etanol route using acetates and alkoxide precursors. They are deposited on alumina substrates. High frequency dielectric properties depend substantially on processing conditions. Dielectric permittivity and tunability increase with the increase of processing temperature due to increased grain size and better crystallinity. The properties also depend on heating regime. Two step annealing is introduced, where the first thin layer of the same composition serves as nucleation layer for the following deposition. Similar procedure is used for K(Ta, Nb)O3 (KTN 60/40) films. The films exhibit high dielectric constant and high tunability. The application of BST film in phase shifting device is demonstrated.