Presenter: Assoc. Prof. Egbert Zojer (Graz University of Technology)
Topic: ElectrostaticDesign of Low-Dimensional Materials and Interfaces
Time: 10:00 AM, Oct.20th (Thursday)
Location: Conference Room B, BLDG 909-1F
Abstract
Forrealizing the promises of organic nano-electronics it is crucial to control thenature of the electronic states within the materials as well as at interfaces.This is commonly achieved through functional chemical substitutions that tunethe properties of individual molecules. Deviating from that approach, we hereportray a largely unexplored strategy that exploits collective electrostaticeffects1 arising from the superposition of the electrical fields ofassembled polar groups. Such effects typically determine the electronic andtransport properties of organic monolayers2 and their consequencesare not always advantageous. When employing them in a well-defined manner, theycan, however, be used for realizing materials with novel properties, asdiscussed here on the basis of DFT-type quantum-mechanical simulations.
For example, we use them to develop a modulartoolbox for relatively complex organic quantum-systems at interfaces includingmonolayer-based quantum-cascades, quantum-wells, and locally spin-sensitivemolecular films.3 First steps towards an experimental realization ofsuch systems are also discussed.4 Additionally, we address howcollective electrostatic effects can be used for tuning the electronicproperties of 2D-like electron systems such as graphene, monolayers ofhexagonal boron-nitride and layered semiconductors.5 Extending theconcepts to bulk materials we, furthermore, propose design strategies forrealizing complex organic frameworks, whose properties are determined by a deliberatealignment of polar building blocks. Common to all those cases is a pronouncedlocalization of the frontier electronic states in different spatial regions ofthe materials and a shift of their energies, both of which can be controlled bythe distribution and value of the used local dipoles.
References
[1] G. Heimel etal. Acc. Chem. Res. 2008, 41: 721; G. Heimel et al. Adv. Mater., 2010, 22:2494; [2] G. Heimel et al., Phys. Rev. Lett., 2006: 193310; G. Heimel et al.,Adv. Mater. 2012, 24: 4403, V. Obersteiner et al., J. Phys. Chem. C 2014, 118:22395; V. Obersteiner et al., J. Phys. Chem. C, 2015, 119: 21198; T. Taucher etal., J. Phys. Chem. C., 2016: 1328; I. Hehn et al. J. Phys.Chem. Lett., 2016, 7: 2994; [3] B. Kretz et al., Advanced Science, 2015,1400016; [4] T. Abu-Husein et al., Adv. Funct. Mater., 2015, 25: 3943; A.Kovalchuk et al., Chemical Science, 2016, 7: 718; A. Kovalchuk et al., RSCAdv., 2016, 6: 69479; [5] G. Kraberger et al., Adv. Mater. Interfaces, 2015,1500323.
Biography
Dr. Zojer is currently leading themodelling activities at the Institute of Solid State Physics at Graz Universityof Technology (Austria), to where he returned after spending several years atthe University of Arizona and the Georgia Institute of Technology (USA). Hepublished ca. 170 peer reviewed papers dealing with organic semiconductors andorganic-inorganic hybrid interfaces, is a member of the editorial advisoryboard of Advanced Functional Materials, and served as member of the condensedmatter physics panel of the European Research Council.
Contact:Prof. Steffen Duhm
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