A strong electro-optically active lead-free ferroelectric integrated on silicon

• Published in: Nature communications 2013-04, Vol.4 (1), p.1671-1671, Article 1671
• Main Authors: Abel, Stefan, Stöferle, Thilo, Marchiori, Chiara, Rossel, Christophe, Rossell, Marta D., Erni, Rolf, Caimi, Daniele, Sousa, Marilyne, Chelnokov, Alexei, Offrein, Bert J., Fompeyrine, Jean
• Format: Article
• Language: English
• Subjects: 639/301/119/996; 639/624/1075/401; 639/624/399/1099; Ferroelectrics; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2695

The development of silicon photonics could greatly benefit from the linear electro-optical properties, absent in bulk silicon, of ferroelectric oxides, as a novel way to seamlessly connect the electrical and optical domain. Of all oxides, barium titanate exhibits one of the largest linear electro-optical coefficients, which has however not yet been explored for thin films on silicon. Here we report on the electro-optical properties of thin barium titanate films epitaxially grown on silicon substrates. We extract a large effective Pockels coefficient of r eff =148 pm V −1 , which is five times larger than in the current standard material for electro-optical devices, lithium niobate. We also reveal the tensor nature of the electro-optical properties, as necessary for properly designing future devices, and furthermore unambiguously demonstrate the presence of ferroelectricity. The integration of electro-optical active films on silicon could pave the way towards power-efficient, ultra-compact integrated devices, such as modulators, tuning elements and bistable switches. The strong electro-optical response of BaTiO 3 could be useful for making high-speed switches for optical telecommunications. Abel et al . demonstrate the ability to maintain this response in BaTiO 3 films grown directly onto silicon, extending its potential to the development of silicon photonics.