Room temperature dc electrical conductivity studies of electron-beam irradiated carbon nanotubes
The influence of electron-beam (E-beam) irradiation on the electrical (electronic) properties of single- (SW) and multi-walled (MW) carbon nanotube grown by microwave chemical vapor deposition is investigated. These films were subjected to a constant energy of 50 keV (50 A/cm2) from a scanning electron microscope gun for 2.5, 5.5, 8.0, and 15 h continuously - such conditions resemble increased temperature and/or pressure regime, enabling a degree of structural fluidity. To assess the structural modifications and electrical properties, the films were analyzed before and after irradiation. The experiments show that with increased exposure to ≥ 8-9 h, occasionally found individual bundles of single-wall nanotubes tend to collapse or pinch, graphitize/amorphize, and oxidize within the area of the electron-beam focus. Dramatic improvement in the I-V properties for single-walled (from semiconducting to quasi-metallic) and relatively small but systematic behavior for multi-walled with increasing exposure is discussed in terms of the critical role of controlled introduction of defects. The contact resistance decreases by orders of magnitude when exposed to electron beam and for all of the measurements the values ranged between 80 Ω and 10 kΩ at room temperature. These results also indicated that multi-walled nanotubes tend to reach a state of saturation degradation assessed by four-probe conductivity measurements. It is suggestive that there may be local gradual re-organization, i.e. sp2 + δ, sp3 C ⇔ sp2 C. More importantly, they provided a contrasting comparison between metallic/semiconducting (single/double-wall) and invariably metallic (multi-wall) carbon nanotubes.
Physics, Astronomy, and Materials Science
Carbon nanotubes, Chemical vapor deposition, Electrical properties, Electron-beam irradiation, Space applications
Gupta, S., R. J. Patel, N. Smith, R. E. Giedd, and D. Hui. "Room temperature dc electrical conductivity studies of electron-beam irradiated carbon nanotubes." Diamond and related materials 16, no. 2 (2007): 236-242.
Diamond and Related Materials