Electric resistance of single-walled carbon nanotubes under hydrostatic pressure

The electric resistance of single-walled nanotube mats has been studied sys tematically under both ambient and high hydrostatic pressures up to 1.5 GPa . Both the temperature dependence of the resistance and the magnetoresistan ce indicate that electrical transport occurs by variable range hopping, app arently in 2D. We suggest that this unexpected dimensionality arises From a fractal network of tubes and bundles. Under hydrostatic pressure (HP) the resistance still shows 2D variable range hopping and decreases with increas ing HP. An irreversible increase in localization length and DOS is induced below 0.5 GPa. The behavior is reversible and due to strong interaction of tubes from 0.5 GPa up to 1.05 GPa. These results indicate that 2D variable range hopping occurs within bundles. (C) 2001 Elsevier Science Ltd. All rig hts reserved.