This research was conducted by a WPI-MANA research group led by Principal Investigator Minoru Osada and Director Takayoshi Sasaki of WPI-MANA at NIMS. Electronic devices are getting smaller all the time, but there is a limit to how small they can get using current materials and technology. High-κ dielectric materials may be the key for developing electronic devices of the future.

Minoru Osada and colleagues created high-performance dielectric nanofilms using 2D perovskite nanosheets (Ca₂Na_m−3Nb_mO_3m+1; m = 3–6) as building blocks. Perovskite oxides offer tremendous potential for controlling their rich variety of electronic properties including high-κ dielectric and ferroelectric.

The researchers demonstrated the targeted synthesis of nanofilms composed of 2D perovskite nanosheets in a unit-cell-upon-unit-cell manner. In this unique system, perovskite nanosheets enable precise control over the thickness of the perovskite layers in increments of ~0.4 nm (one perovskite unit) by changing m, and such atomic layer engineering enhances the high-κ dielectric response and local ferroelectric instability. The m = 6 member (Ca₂Na₃Nb₆O₁₉) attained the highest dielectric constant, ε_r = ~470, ever realized in all known dielectrics in the ultrathin region of less than 10 nm.

Perovskite nanosheets are of technological importance for exploring high-κ dielectrics in 2D materials, which have great potential in electronic applications such as memories, capacitors, and gate devices. Notably, perovskite nanosheets afforded high capacitances by relying on high-κ values at a molecular thickness. Ca₂Na₃Nb₆O₁₉ exhibited an unprecedented capacitance density of approximately 203 μF cm^-2, which is about three orders of magnitude greater than that of currently available ceramic condensers, opening a route to ultra-scaled high-density capacitors.

These results provide a strategy for achieving 2D high-κ dielectrics/ferroelectrics for use in ultra-scaled electronics and post-graphene technology.

"Atomic Layer Engineering of High‑κ Ferroelectricity in 2D Perovskites"
Bao-Wen Li, Minoru Osada, Yoon-Hyun Kim, Yasuo Ebina, Kosho Akatsuka, and Takayoshi Sasaki
Journal : J. Am. Chem. Soc. 139, 10868−10874 (2017)
DOI : 10.1021/jacs.7b05665

International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan

National Institute for Materials Science
1-1 Namiki, Tsukuba, Ibaraki 305-0044 Japan
Phone: +81-29-860-4710
E-mail: mana-pr[AT]nims.go.jp