Study On Elliptic Polarization Spectra Of Temperature - Dependent Titanium Dioxide And Lead Zirconate Titanate Thin Films

Spectroscopic ellipsometry (SE) is a non-destructive and non-contacting measurement method, since its mechanism is suitable for film detecting; it has become one of the most important technology to investigate the optical properties of thin films. At the same time, TiO2 and PZT thin films are used for optical waveguide and optical modulator. With integration level increasing, the induced heat influence on device performance has become one of the most important projects. In this paper, we have studied TiO2 and PZT thin films and spectroscopic ellipsometry with temperature parameter variation. The main contents are listed:We analyze the temperature dependence of optical constant for TiO2 thin film based on Forouhi-Bloomer dispersion model. The variable temperature spectroscopic ellipsometry has been used to realize the measurement of ellipsometry parameter under different temperature and dispersion curve. The refractive index of TiO2 has decreased with the temperature increasing, which indicate the influence of heat induced expansion to the film density. The red-shift tendency in extinction curve of TiO2 thin film is attributed to heat-induced band gap and electronic lifetime in band energy.PZT thin film has been prepared by Pulse Laser Deposition (PLD) and fitted by Forouhi-bloomer dispersion model for optical constant and band gap. The band gap obtained from spectroscopic ellipsometry can approach the value from first principle law, which proved our result credible. And then the optical constants of PZT thin films under different temperature have been measured by variable temperature spectroscopic ellipsometry. The phase transition point has been obtained for 320 ℃. The result shows that variable temperature spectroscopic ellipsometry can be used to analyze band gap shift and phase transition of some ferroelectric materials.