The research group led by prof. Tetsuya Hasegawa (the University of Tokyo) synthesized single crystalline thin films of transition metal oxynitrides, and succeeded in controlling their coordination structure of oxygen and nitrogen ions around a metal cation for the first time.

Mixed-anion compounds including two or more anion species show various physical and chemical properties depending on their coordination structure, i.e. anion arrangement around a metal cation, in a crystal. However, synthetic route for controlling coordination structure has not been established. In this study, the research group synthesized single crystalline thin films of tantalum oxynitrides under compressive strain from the substrates, and found that coordination structure of the oxynitride can be controlled by the strain. While only the most thermodynamically stable cis-type structure was obtained under small strain, metastable trans-type structure appears by increasing the lattice strain. Such control of coordination structure in oxynitride will result in novel optical and/or electronic materials such as visible-light active ferroelectrics.

　

【Paper title and author(s)】

• Title: Strain Engineering for Anion Arrangement in Perovskite Oxynitrides
• Author(s): Daichi Oka, Yasushi Hirose, Fumihiko Matsui*, Hideyuki Kamisaka, Tamio Oguchi, Naoyuki Maejima, Hiroaki Nishikawa, Takayuki Muro, Kouichi Hayashi, and Tetsuya Hasegawa
  * NAIST
• Publication: 「ACS Nano」 (online)
  http://pubs.acs.org/doi/abs/10.1021/acsnano.7b00144