Ellipsometric Investigations of the Refractive Index Depth Profile in PZT Thin Films

Optical investigations of self-polarized PbZr_0.235Ti_0.765O₃ (PZT) films deposited onto Si/SiO₂/adhesion layer/(111) Pt substrate by RF sputtering are presented in this work. Measurements were performed with a spectral ellipsometer working in rotating analyzer mode. To obtain the temperature dependence of optical constants, a specially constructed heating device was applied. For ellipsometric data fitting a multilayer model in common with the Bruggeman Effective Medium Approximation (EMA) was used. It enables us to obtain the depth profiles of the refraction index of PZT films. For the first time, the presence of a space charge induced refractive index profile near the bottom Pt electrode at 500 °C was proved.