Far-infrared ferroelectric soft mode spectroscopy on thin films

Review on first quantitative far-infrared transmission measurements of the ferroelectric soft-mode response is given on several perovskite ferroelectr ic, antiferroelectric, relaxor ferroelectric and incipient ferroelectric fi lms. The following films, mostly prepared by sol-gel technique on a sapphir e substrate (film thickness from 100 to 1000 nm) were investigated: PbTiO3, PbZrO3, PbZr0.53Ti0.47O3, PbZr0.75Ti0.25O3, PLZT 9.5/65/35, 8/65/35, 2/95/ 5, SrTiO3, BaTiO3, Ba0.35Sr0.65TiO3, Ba0.65Sr0.35TiO3, and PbSc0.5Ta0.5O3. Whereas in the PZT system the soft mode parameters do not substantially dif fer from those in bulk materials, in the BST system dramatic differences ha ve been observed, particularly in SrTiO3 at low temperatures. Low-frequency dielectric properties are also discussed.