Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: Symposium: Atomic Wires at Surfaces II
(Invited Speakers: Erio Tosatti, Serge Lemay, Shuji Hasegawa)

O 35.5: Hauptvortrag (ohne Erstattung)

Dienstag, 26. Februar 2008, 15:30–16:00, HE 101

Simultaneous electrical transport and scanning tunneling spectroscopy of carbon nanotubes — Brian J. LeRoy, Iddo Heller, Vijay K. Pahilwani, Jing Kong, Cees Dekker, and •Serge G. Lemay — Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands

Using scanning tunneling spectroscopy, we demonstrate that current directly injected into a freely suspended individual single-wall carbon nanotube can be used to excite, detect and control a specific vibrational mode of the molecule. Electrons tunneling inelastically into the nanotube cause a non-equilibrium occupation of the radial breathing mode, leading to both stimulated emission and absorption of phonons by successive electron tunneling events. We exploit this effect to estimate a quality factor of well over 10,000 for this nanomechanical oscillator. We further employ the suspended geometry to perform scanning tunneling spectroscopy measurements on single-walled carbon nanotubes with independently addressable source and drain electrodes in the Coulomb blockade regime. This three-terminal configuration allows the coupling to the source and drain electrodes to be quantitatively measured, which we exploit to demonstrate that electrons were added to spin-degenerate states of the carbon nanotube. Unexpectedly, the Coulomb peaks also show a strong spatial dependence. By performing simultaneous scanning tunneling spectroscopy and electrical transport measurements we show that the probed states are extended between the source and drain electrodes and that the observed spatial dependence thus reflects a tip-induced modulation of the contact resistance.