Pyroelectric Properties of Lead Based Ferroelectric thin Films

Lead based thin ferroelectric films have been prepared using both sol-gel and dual ion beam sputtering (DIBS) processes. Material compositions within the PbTiO3 and PLZT system have been deposited by both techniques onto metallised silicon. By using a standard sol-gel prepared solution, modified with acetylacetone and spin-coating, lµm thick fully perovskite layers, were obtained at low temperature (450°) with some preferred orientation. The grain size was in the range 0.2-0.4µm. A dielectric constant of 400 and a reversible pyroelectric coefficient of 1.2 × 10−4Cm−2K−1 were obtained. In contrast, a range of capping layers (SiO2, A12O3, BPSG) on silicon have been investigated using the DIBS process. Highly crystalline (100) and (111) films were readily produced at temperatures in excess of 550°, at a growth rate of 0.3µm/hour. Control of stoichiometry has also been studied in detail, by sputtering of a composite metal-ceramic target with a high energy Kr beam and by bombarding the growing film with a low energy oxygen ion-beam. Dielectric constants of 200-300, losses below 0.015 and resistivities above 1010Ωm have been achieved. A pyroelectric coefficient of the order of 2.5 × 10−4Cm−2K-1, pre-poled for a La-doped film on BPSG capped Si was obtained, which did not increase significantly on poling.