Dipole-Oriented Molecular Solids Can Undergo a Phase Change and Still Maintain Electrical Polarization

Journal Article · Sun Oct 02 00:00:00 EDT 2016 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.6b07296· OSTI ID:1346621

Cassidy, Andrew ^[1]; Jørgensen, Mads R. V. ^[2]; Rosu-Finsen, Alexander ^[3]; Lasne, Jérôme ^[3]; Jørgensen, Jakob H. ^[1]; Glavic, Artur ^[4]; Lauter, Valeria ^[4]; Iversen, Bo B. ^[2]; McCoustra, Martin R. S. ^[3]; Field, David ^[1]

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1. Aarhus Univ. (Denmark). Dept. of Physics and Astronomy
2. Aarhus Univ. (Denmark). Dept. of Chemistry. Center for Materials Crystallography
3. Heriot-Watt Univ., Edinburgh, Scotland (United Kingdom). Inst. of Chemical Sciences
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division

It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 10⁸ V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. In this paper, we present the first in situ structural characterization of a representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. Finally, this reinforces the spontelectric model as a means of describing long-range dipole–dipole interactions and points to a new type of ordering in molecular thin films.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); Danish National Research Foundation (Denmark)
• DOE Contract Number: AC05-00OR22725; DNRF93
• OSTI ID: 1346621
• Journal Information: Journal of Physical Chemistry. C, Vol. 120, Issue 42; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
materials
molecular film
neutron scattering
spectroscopy
polarisation