ORIGINAL PAPER Temperature dependence of optical and structural properties of ferroelectric B 3.15 Nd 0.85 Ti 3 O 12 thin film derived by sol–gel process Yongyuan Zang • Dan Xie • Yu Chen • Mohan Li • Chen Chen • Tianling Ren • David Plant Received: 4 August 2011 / Accepted: 24 October 2011 / Published online: 9 November 2011 Ó Springer Science+Business Media, LLC 2011 Abstract We report the annealing temperature depen- dence of optical properties in ferroelectric B 3.15 Nd 0.85 Ti 3 O 12 (BNdT) thin film for the first time. BNdT thin films are pre- pared by a sol–gel/spin coating method. Structural properties of BNdT thin films upon different thickness and annealing temperatures are characterized using the X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The BNdT thin film annealed at 650 °C exhibits a well defined perovskite crys- talline structure with high c-axis orientation, which leads to a saturated polarization–electric field (PE) hysteresis with a remanent polarization of 2P r = 39.6 lC/cm 2 and coercive field of 85 kV/cm at 5 V. Little fatigue degradation ( \ 5%) is demonstrated upon 1 9 10 10 switching cycles indicating a good fatigue endurance. Additionally, a superior optical transparency T(k) of[ 80% is observed for wavelengths from 250 to 2,000 nm. Fundamental optical parameters of BNdT material such as refractive index n, extinction coefficient k, and band gap energy E g are extracted from an ellipsometry measurement. Microstructure and annealing temperature dependence of T(k), n, k, and E g variation are also investi- gated and explained in detail. Keywords Ferroelectrics  BNdT thin film  Optical properties  Sol–gel process 1 Introduction Ferroelectric thin films are considered as promising candi- dates for many electrical and optical applications, such as ferroelectric random access memory (FeRAM), piezoelec- tric transducers, high dielectric capacitors, optical wave- guides and modulators, due to their remarkable ferroelectric, piezoelectric, and electro-optic properties [1–4]. Increasing attention is devoted to the application of ferroelectric thin films for electro-optic devices, due to their superior proper- ties compared to traditional bulk materials. For example, ferroelectric thin films require small electrical fields and therefore they are promising materials for optical modulators with lower power consumption, better sensitivity, and faster switching speeds. This potential has been demonstrated in the Fabry–Perot interference modulator, where a large phase shift is achieved in a ferroelectric film with a micrometer- scale thickness [5–7]. Ferroelectric films have also been used to improve optical mode matching between an optical fiber and a waveguide device [8]. Among ferroelectric thin films, the lead zirconate tita- nate (PZT) material has been exploited extensively for various electrical [9–11] and optical [12–14] applications, due to its high remanent polarization value, high optical transmission, and strong electro-optic Kerre effect. How- ever, PZT thin films are known to exhibit low fatigue endurance, especially when the platinum is used as Y. Zang (&)  C. Chen  D. Plant Electrical and Computer Engineering, McGill University, Montreal, QC H3A 2T8, Canada e-mail: yongyuan.zang@mail.mcgill.ca D. Xie  Y. Chen  T. Ren Tsinghua National Laboratory for Information Science and Technology (TNList), Institute of Microelectronics, Tsinghua University, Beijing 100084, People’s Republic of China D. Xie State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, People’s Republic of China M. Li Chemical Engineering, McGill University, Montreal, QC H3A 2B2, Canada 123 J Sol-Gel Sci Technol (2012) 61:236–242 DOI 10.1007/s10971-011-2619-0 Author's personal copy