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The 15th International Conference on

Vibrations at Surfaces

June 22-26, 2015 ▪ Donostia-San Sebastián, Spain

Donostia Igeldotik

Program

OverviewMondayTuesdayWednesdayThursdayFriday

Tuesday June 23

09:00-10:40 Tu1: Transport in electronic devices
10:40-11:20 Coffee break
11:20-13:00 Tu2: Surface diffusion and migration
13:00-15:30 Lunch break (on your own)
15:30-16:40 Tu3: Chemistry and growth of graphene
16:40-17:20 Coffee break
17:20-18:50 Tu4: Electron-phonon coupling in graphene
19:00-21:30 Poster session A

Tu1: Transport in electronic devices

Chair: D. Sanchez-Portal, San Sebastián, Spain

09:00-09:30 K. Hannewald, Berlin, Germany
Polaron transport in organic crystals: theory and modelling
09:30-10:00 M. Reed, New Haven, USA
IETS of single molecule transistors
10:00-10:20 H. Okuyama, Kyoto, Japan
Environmental control of single-molecule conductance
10:20-10:40 S. Wang, Dübendorf, Switzerland
Electronic and vibronic properties of atomically precise bilayer graphene nanoribbons

Invited talk

Polaron transport in organic crystals: theory and modelling

K. Hannewald

Institut für Physik, Theoretische Festkörperphysik, Humboldt-Universität zu Berlin, Germany

The charge-carrier mobility of organic semiconductors is a fundamental material property and one of the central quantities for the optimization of device performance in, e.g., organic transistors and organic/hybrid solar cells. In order to investigate the intrinsic fundamental (i.e., not device-specific) charge-transport phenomena in organic solids, molecular crystals are ideal candidates because of their high degree of structural order. Nonetheless, even for such ultrapure organic crystals, the theoretical and numerical description of the charge transport is a highly nontrivial task due to the strong coupling between the electronic and vibronic degrees of freedom.

In this talk, I will present a theory for charge transport in organic crystals which generalizes Holstein's small polaron model to polarons of arbitrary size and allows to calculate the carrier mobilities using ab-initio techniques (density-functional theory). The generalized mobility expression includes both the coherent band transport as well as the thermally induced hopping on equal footing. As a prototypical example, the theory is applied to herringbone-stacked crystals where the temperature dependence of the mobilities is simulated and compared to experimental data. Finally, the mobility anisotropy is analyzed by a novel 3D visualization technique for the relevant transport channels.

[1] K. Hannewald et al., Phys. Rev. B 69, 075211 & 075212 (2004)

[2] K. Hannewald and P.A. Bobbert, Appl. Phys. Lett. 85, 1535 (2004)

[3] F. Ortmann, F. Bechstedt, and K. Hannewald, Phys. Rev. B 79, 235206 (2009)

[4] F. Ortmann, F. Bechstedt, and K. Hannewald, New J. Phys. 12, 023011 (2010)

[5] F. Ortmann, F. Bechstedt, and K. Hannewald, Phys. Stat. Sol. B 248, 511 (2011)

[6] D. Nabok, C. Draxl, and K. Hannewald, Acc. Chem. Res. 47, 3225 (2014)