In situ resistance measurements of strained carbon nanotubes

We investigate the response of multiwalled carbon nanotubes to mechanical s train applied with an atomic force microscope probe. We find in some sample s, changes in the contact resistance dominate the measured resistance chang e. In others, strain large enough to fracture the tube can be applied witho ut a significant change in the contact resistance. In this case, we observe that enough force is applied to break the tube without any change in resis tance until the tube fails. We have also manipulated the ends of the broken tube back in contact with each other, re-establishing a finite resistance. We observe that, in this broken configuration, the resistance of the sampl e is tunable to values 15-350 k Ohm greater than prior to breaking. (C) 199 9 American Institute of Physics. [S0003-6951(99)01244-9].