| AVS 61st International Symposium & Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS+TF-ThM |
| Session: | Organic Layers on Surfaces |
| Presenter: | Axel Enders, University of Nebraska-Lincoln |
| Authors: | A. Enders, University of Nebraska-Lincoln D.A. Kunkel, University of Nebraska-Lincoln A. Sinitskii, University of Nebraska-Lincoln S. Simpson, University at Buffalo-SUNY J. Hooper, Jagiellonian University, Poland E. Zurek, University at Buffalo-SUNY |
| Correspondent: | Click to Email |
We will present an experimental study on the self-assembly and electronic properties of the organic ferroelectrics, croconic acid (CA), 3-hydroxyphenalenone (3-HPLN), and the related compound rhodizonic acid (RA) on crystalline metal surfaces. Importantly, the bond polarization of the selected organics is highly planar. This provides the foundation for the development of 2D polarization patterns by design, including rather complex ones like the honeycomb pattern recently discovered by our group [1]. What is remarkable about those honeycomb networks of CA, is that the interaction with the substrate is key to ferroelectric switching barriers. Also the structurally related 3-HPLN forms linear chains on surfaces that are expected to exhibit 2D polarization ordering within the plane of the 2D organic layer. The molecular arrangement can be manipulated through the use of the substrate and growth conditions, and we have also identified a new, chiral phase of hydrogen-bonded trimers of 3-HPLN. This surface-science approach was key to the first reported synthesis of RA crystalline structures [2]. Here we present an overview over the structural phases of select organic ferroelectrics on surfaces and how ordered 2D polarization states can emerge. Importantly, we discovered by co-deposition of CA and 3-HPLN that they form ordered 2D co-crystalline phases. ). The structure of the resulting networks can be tuned by varying the relative concentration of the organics. Namely, for equal ratios of CA and 3-HPLN two polymorphs are observed, while for 2/1 CA/3-HPLN ratio, only a single structure is found. Transitions from CA rich structures to CA poor structures can be induced through weak annealing, in which the smaller CA desorbs before 3-HPLN. We expect that important ferroelectric properties of organic ferroelectrics, such as their ordering temperature and switching fields, can be manipulated through co-crystallization. We will highlight how surface science studies, specifically STM, can help accelerate co-crystal discovery.
References:
[1] D. A. Kunkel, et al. Phys. Rev. B 87, 041402 (2012).
[2] D. A. Kunkel, et al. J. Phys. Chem. Lett. 4, 3413 (2013).