| Four-Point Resistance of Nanotubes |
May, 3 (2006) at 4pm Adrian Bachtold We have studied the resistance of single-wall carbon nanotubes (SWNT) measured in a four-point configuration with noninvasive voltage electrodes (1). The voltage drop is detected using multiwalled carbon nanotubes while the current is injected through nanofabricated Au electrodes. The resistance at room temperature is shown to be linear with the length as expected for a classical resistor. This changes at cryogenic temperature; the four-point resistance then depends on the resistance at the Au-SWNT interfaces and can even become negative due to quantum-interference effects. In the second part of this talk, I report a new method to access the electronic paths in multiwalled carbon nanotubes (MWNT) which enables the first estimation of the intershell resistance (2). Using four-point measurement techniques, the voltage drop is measured between electrodes situated inside or outside the region lying between the current biased electrodes. Surprisingly, a significant nonlocal voltage drop is detected at room temperature. This result is in agreement with a model which considers conduction through the two outermost shells and treats them as a resistive transmission line. In such a model, the intershell conductance is 10 kohm/Nm. This value is in agreement with the estimate based on electrons tunnelling through atomic orbitals of nearby shells while taking into account conservation of energy but not momentum. (1) B. Gao, Y.F. Chen, M.S. Fuhrer, D.C. Glattli, A. Bachtold, Phys. Rev. Lett. 95, 196802 (2005). (2) B. Bourlon, C. Miko, L. Forrs, D.C. Glattli, A. Bachtold, Phys. Rev. Lett. 93, 176806 (2004). |