Low-temperature radiation damage studies in single-walled carbon nanotube bundles by hopping conductance

Abstract

The paper shows the results of studying radiation defects in single-walled carbon nanotube bundles at low temperatures. The data were obtained in a unique experiment that inseparably combines 1 MeV electron irradiation at a temperature of ∼10 K and electrical conductivity measurements over a wide temperature range of 5–300 K. The experiment allowed us to reveal and separate the influence of stable and unstable radiation defects on the electrical properties of SWCNTs. It is shown that the 2D Mott variable range hopping conduction regime exhibits resistance to electron irradiation. The hopping conductivity is the dominant charge transfer mechanism in the temperature range of 5–50 K in both the pristine and irradiated SWCNT samples. It was found that the parameters of hopping transport demonstrate high sensitivity to the introduction and annealing of radiation defects. The low-temperature electron irradiation revealed the possibility of the emergence of an additional conduction channel in the irradiated SWCNTs. This channel demonstrates thermally activated behavior with a low activation energy of ∼0.5 meV at temperatures of 5–50 K. The obtained data indicate that unstable radiation defects create conditions for the possibility of impurity band conduction in SWCNT bundles.