Contacting carbon nanotubes selectively with low-ohmic contacts for four-probe electric measurements

Contact resistances of multiwalled nanotubes deposited on gold contact fingers are very large. We show that the contact resistances decrease by orders of magnitudes when the contact areas are selectively exposed to the electron beam in a scanning electron microscope. The focused electron beam enables the selection of one particular nanotube for electrical measurement in a four-terminal configuration, even if a loose network of nanotubes is deposited on the gold electrodes. For all measured nanotubes, resistance values lie in a narrow range of 0.35-2.6 k Omega at room temperature. (C) 1998 American Institute of Physics. [S0003-6951 (98)04228-4].