Abstract: Calcium-modified lead titanate thin films deposited on si(100) substrate were prepared by sol-gel processing. The ellipsometric spectra of the PCT
ferroeclectric thin films were obtained in the spectral range of 2.3-5.0eV, and their optical constants(the refractive index n and the extinction
coefficient k) were determined. It was found that the peaks of the refractive indexes of the PCT thin films shift to the low energy region, their
absorption edges shift to lower energy with an increase in Ca doping, this suggests that the energy gap reduces after Ca ions occupied Pb ions sites.
The reasons of these shifts were also discussed.

Key words: ellipsometry, optical constants, ferroelectric films