Program Highlights

Nanostructures with a Twist

Axel Enders, Xiao Chen Zeng, and Stephen Ducharme
Nebraska MRSEC

 Scott Simpson and Eva Zurek
SUNY Buffalo

 Timothy Usher
California State University at San Bernardino

The recent discovery of room temperature ferroelectricity in crystalline croconic acid has drawn attention to proton-ordered organic ferroelectrics. What is special about these materials is that an applied electric field reverses the electric polarization within the molecular plane via proton displacement. This implies that for ferroelectricity to occur, three-dimensional crystal structures are not required, which is in contrast to archetypical hydrogen-bonded ferroelectrics such as KDP.

Nebraska MRSEC researchers, in collaboration with their partners, have accomplished to grow large-scale two-dimensional layers of croconic acid molecules. The confinement of the molecules to the surface results in hydrogen bonded planar networks, which contain only molecules of the same chirality and thus exhibit a chiral, or handed, architecture. It was shown through first-principles calculations that the two-dimensional character of the experimentally found structures, in combination with the substrate, promote polarization ordering within the sheets [Phys. Rev. B. 87, 041402 (2013)].

This demonstration of the control of polarization in 2D organic sheets could potentially guide the design and manipulation of organic structures, fabricated with molecular precision for applications in information processing and ultrahigh density data storage. This could include unexplored technologies, such as molecular logic and active polarization networks.

These programs are supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0820521.

Scanning tunneling microscopy image of a 2D network of croconic acid molecules.