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Oxide Nanosheets: Old 2D Materials, New Challenges?

Minoru Osada (NIMS and Waseda University, Japan)
Fri, 13/02/2015 - 2:00pm to 3:00pm
Graphene Theory Common Seminar Room (S16-06)
Barbaros Özyilmaz
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2D nanosheets with atomic or molecular thickness have been emerging as important due to their unique properties. Inspired by the intriguing properties of graphene, many efforts have been devoted to synthesising 2D inorganic nanosheets of various materials including metal oxides, hydroxides, and transition-metal chalcogenides as well as primarily investigating their unique electronic structures and physical properties. Among various types of inorganic nanosheets, oxide nanosheets are important, fascinating research targets because of the virtually infinite varieties of layered oxide materials with interesting functional properties. We are working on the creation of new oxide nanosheets and the exploration of their novel functionalities in electronic applications [1,2].

A variety of oxide nanosheets (such as Ti1-O2, Ti1-xCoxO2, MnO2, and perovskites) were synthesized by delaminating appropriate layered precursors into their molecular single sheets via soft- chemical process. These oxide nanosheets have distinct differences and advantages compared with graphene because of their potential to be used as insulators, semiconductors, and even conductors, depending on their composition and structures. Recently, we found that titania- or perovskite-based nanosheets exhibit superior high- performance (r = 100–320) even at a few-nm thicknesses, essential for next-generation electronics. Additionally, nanosheet-based high- capacitors exceeded textbook limits, opening a route to new capacitors and energy storage devices.

Another attractive aspect is that oxide nanosheets can be organized into various nanoarchitectures by applying solution-based layer-by-layer assembly. Sophisticated functionalities or nanodevices can be designed through the selection of nanosheets and combining materials, and precise control over their arrangement at the molecular scale. We utilized oxide nanosheets as building blocks in the LEGO-like assembly, and successfully developed various functional nanodevices such as all nanosheet FETs, artificial ferroelectrics, spinelectronic devices, magneto-plasmonic materials, Li-ion batteries, etc. Our work is a proof-of-concept, showing that new functionalities and nanodevices can be made from nanosheet architectonics.

[1] M. Osada and T. Sasaki, J. Mater. Chem. 19, 2503 (2009) [Review].
[2] M. Osada and T. Sasaki, Adv. Mater. 24, 210 (2012) [Review].

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