MEASUREMENT OF ELECTROOPTIC PROPERTIES OF FERROELECTRIC THIN-FILMS USING THE ULTIMATE ELLIPSOMETER

Ferroelectric(FE) films constitute an important component of electro-o ptic devices; such films have been used for second harmonic generation , spatial light modulators and optical switches. FE films typically yi eld large values of linear and quadratic electro-optic coefficients. M ost electric field induced birefringence measurements have been made w ith transverse electrodes, i.e. with light beam between poled electrod es. In the present study, an Ultimate Ellipsometer was used; a HeNe la ser was directed perpendicularly through FE capacitors with applied vo ltages and the phase change monitored. The layout of this device is di scussed in details. Sol-gel derived PST 53/47 and PLZT 28/0/100 films were prepared on conductive glass substrates. 0.5M precursor solutions based on the stoichiometric amounts of Pb acetate, La nitrate and Ti/ Zr alkoxides were refluxed for 1 hour and spincoated on the substrates under clean room conditions. The films were then fired to 550C to cry stallized them to single phase perovskite. Top Au/Pd electrodes were d eposited to form an array of monolithic PZT and PLZT capacitors. The r efractive indices and extinction coefficients of the films were also o btained using multiangle ellipsometry. With applied voltages, the indu ced birefringences were measured, resulting in typical birefringence-v oltage butterfly Ioops. The linear electro-optic coefficients of the f ilms were then calculated. The linear electrooptic coefficients of PLZ T 28/0/100 and PZT 53/47 were measured to be 59 and 315 pm/V, respecti vely. The latter value represents the highest reported for any ferroel ectric film.