Presentation Title

Croconic Acid : Surface and Electric Field Influence on Deposition

Faculty Mentor

Dr. Kimberley Cousins

Start Date

17-11-2018 10:15 AM

End Date

17-11-2018 10:30 AM

Location

C327

Session

Oral 2

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Croconic Acid (CA) deposition into a thin-film has been of recent interest since single crystal CA is a known organic ferroelectric. In our studies of croconic acid on silica (SiO2) and gold (Au) surfaces, we developed models to explain the fundamental differences in deposition properties on such surfaces with and without an applied electric field. In particular, needle-like structures of CA form when an electric field is not applied, while an ordered thin film forms with a strong electric field. We used plane wave density functional theory (DFT) within the VASP program to calculate surface structures and dynamics. These methods from DFT, computationally allow us to model the fundamental behaviors in deposition which can be used to predict behaviors a molecule can have on an array of surfaces. Optimal surface structures were first determined before the addition of CA in the calculations could be inputted for analysis. The surfaces were chosen from the experimental work where they chose gold as the preferred surface since it serves at an electrode, which is needed to shift the polarization of the film. Silicon dioxide was also modeled to support the experimental findings. Each of the surfaces showed a unique influence in CA deposition. A pure alpha silica surface showed strong interactions where CA chemisorbed to the surface and a covalent bond was generated. A gold (111) surface showed little interactions, where a single CA molecule always orientates itself close to the surface and interacts more preferably with another CA on the surface as a dimer system. In a dimer system on a gold surface, when a 0.1 eV/Å electric field perpendicular to the surface is applied, the preferred pleaded motif of CA crystal structure is favored. This pleaded orientation is analogous to the idealized crystal that should give the best ferroelectric response.

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Nov 17th, 10:15 AM Nov 17th, 10:30 AM

Croconic Acid : Surface and Electric Field Influence on Deposition

C327

Croconic Acid (CA) deposition into a thin-film has been of recent interest since single crystal CA is a known organic ferroelectric. In our studies of croconic acid on silica (SiO2) and gold (Au) surfaces, we developed models to explain the fundamental differences in deposition properties on such surfaces with and without an applied electric field. In particular, needle-like structures of CA form when an electric field is not applied, while an ordered thin film forms with a strong electric field. We used plane wave density functional theory (DFT) within the VASP program to calculate surface structures and dynamics. These methods from DFT, computationally allow us to model the fundamental behaviors in deposition which can be used to predict behaviors a molecule can have on an array of surfaces. Optimal surface structures were first determined before the addition of CA in the calculations could be inputted for analysis. The surfaces were chosen from the experimental work where they chose gold as the preferred surface since it serves at an electrode, which is needed to shift the polarization of the film. Silicon dioxide was also modeled to support the experimental findings. Each of the surfaces showed a unique influence in CA deposition. A pure alpha silica surface showed strong interactions where CA chemisorbed to the surface and a covalent bond was generated. A gold (111) surface showed little interactions, where a single CA molecule always orientates itself close to the surface and interacts more preferably with another CA on the surface as a dimer system. In a dimer system on a gold surface, when a 0.1 eV/Å electric field perpendicular to the surface is applied, the preferred pleaded motif of CA crystal structure is favored. This pleaded orientation is analogous to the idealized crystal that should give the best ferroelectric response.