Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 104: Transport: Molecular electronics (TT with CPP/HL/MA/O)
HL 104.7: Vortrag
Freitag, 20. März 2015, 11:15–11:30, H 0110
Significant role of end groups in electrical transport through molecules — •Karthiga Kanthasamy1, Markus Ring2, Fabian Pauly2, Christoph Tegenkamp1, and Herbert Pfnür1 — 1Institut für Festkörperphysik, Leibniz Universität, Hannover, Germany — 2Fachbereich Physik, Universität Konstanz, Germany
Mechanically controllable break junction (MCBJ) technique is used to investigate the electronic properties of ferrocene and phenyl based molecules with different end groups. Stepwise changes in conductance are observed below 1Go after insertion of the molecules. The junctions are opened in vacuum and IV curves are measured for various distances between the electrodes. Detailed analysis of IV curves shows characteristic peaks in the first-order derivative for ferrocene dithiol (FDT) molecules, which are absent in ferrocene diamine (FDA) and biphenyl dithiol (BPDT). For FDT, in the range of 0.56Go to 0.09Go, there are two symmetric peaks, whose energy difference increases from 60 meV to 160 meV with increasing contact distance. Above 0.56Go or below 0.01Go, symmetric peaks are absent. The FDT molecules show typically a one order of magnitude higher conductance than FDA and BPDT. The IV graph for FDT is linear, i.e., it has metallic characteristics, while FDA and BPDT are dominated by tunneling. Theoretical calculations for the molecules in different configurations between the gold electrodes are performed based on density functional theory and the non-equilibrium Green's function formalism. Both elastic transport properties and inelastic electron tunneling spectra are studied to explain the experimental observations.