Pyroelectric properties of lead based ferroelectric thin films

Lead based thin ferroelectric films have been prepared using both sol-gel dual ion beam sputtering (DIBS) processes. Material compositions within the PbTiO₃ and PLZT system have been deposited by both techniques onto metallized silicon. By using a standard sol-gel prepared solution, modified with acetylacetone and spin-coating, 1μm thick fully perovskite layers, were obtained at low temperature (450°C) with some preferred orientation. the grain size was in the range 0.2-0.4 μm. A dielectric constant of 400 and a reversible pyroelectric coefficient of 1.2 × 10^-4 Cm^-2K^-1 were obtained. In contrast, a range of capping layers (SiO₂, Al₂O₃, 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°C, 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.