| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF+AS+NS+SA-ThA |
| Session: | Thin Film: Growth and Characterization, Optical and Synchrotron Characterization II |
| Presenter: | Vaishali Batra, The University of Alabama |
| Authors: | V. Batra, The University of Alabama S. Kotru, The University of Alabama V.N. Harshan, The University of Alabama M. Varagas, University of Texas at El Paso C.V. Ramana, University of Texas at El Paso |
| Correspondent: | Click to Email |
Lanthanum doped lead zirconate titanate (PLZT) of perovskite type crystalline structure is an interesting transparent ferroelectric material due to its large remnant polarization and electro-optic effects, near the morphotropic phase boundary. The excellent optical and electrical properties make it material of choice for applications in MEMS, optical modulators/transducers and smart sensors. Recent studies reveal that this material possesses great potential for use in future photovoltaic (PV) devices which involves combination of optical transparency and ferroelectric properties. The advantage of using this material for PV applications is that the effect can be realized without a need of p-n junction as in semiconductor devices. Additionally the material exhibits bulk PV effect due to internal electric field originating from electric polarization. However, the optimization of processing conditions of deposited films is important to design efficient devices, which require understanding of the structure, its behavior with light, and response to electric field.
Lanthanum-modified lead zirconate titanate (PLZT) thin films with a composition of (Pb0.95La0.05)(Zr0.54Ti0.46)O3 were deposited on Pt/TiO2/SiO2/Si substrates. The films were rapidly annealed in the temperature range of 550 to 750 °C in oxygen ambient to study the effect of crystallization on the electric and optical properties. X-ray diffraction revealed that the post deposition temperature changes the preferential orientation of the films. Optical band gap values determined from UV-visible spectroscopy and spectroscopic ellipsometry for PLZT films were found to be in the range of 3.42-4.00 eV. The optical constants and their dispersion profiles for PLZT films were also determined from SE analyses. PLZT films exhibit an index of refraction ~2.5 (λ=630 nm). The electrical properties were studied using the model for metal-ferroelectric-metal (MFM) heterostructures with Schottky contacts using Au electrodes. High remnant polarization (41.85 µC/cm2), low coercive voltage (1.19 V) and high free carrier concentration (~1.1x1018 cm-3) were obtained from films annealed at 750 °C. Thus post deposition annealing temperature plays a major role in deciding the electrical and optical properties.