Reversible Metal−Insulator Transitions in Metallic Single-Walled Carbon Nanotubes

Abstract

We report on reversible metal to insulator transitions in metallic single-walled carbon nanotube devices induced by repeated electron irradiation of a nanotube segment. The transition from a low-resistive, metallic state to a high-resistive, insulating state by 3 orders of magnitude was monitored by electron transport measurements. Application of a large voltage bias leads to a transition back to the original metallic state. Both states are stable in time, and transitions are fully reversible and reproducible. The data is evidence for a local perturbation of the nanotube electronic system by removable trapped charges in the underneath substrate and excludes structural damage of the nanotube. The result has implications for using electron-beam lithography in nanotube device fabrication.

Low-energy electron irradiation of preheated and gas-exposed single-wall carbon nanotubes

“…The superscript "a" means "armchair". Figure 14 shows the band structure of three types of armchair nanotubes: (3,3), (5,5) and (9,9). Also shown is the general band region for armchair nanotubes with red representing the conduction band and blue representing the valence band.…”

“…An illustration of the band structure for zigzag type nanotubes is given in Figure 16 showing the band structure of six (n,0) zig-zag nanotubes where n = 5,6,7,8,9,10. The band structures of (6, 0) and (9, 0) have no band gap while those of (5, 0), (7,0), (8,0) and (10,0) show a band gap.…”

“…Studies have also shown that low-energy electron irradiation of isolated SWCNTs induces a transition from metal-to-semiconductor or metal-to-insulator [4,5,10,12], a discovery of particular utility since it shows that low-energy electron irradiation can be used to modify isolated SWCNTs producing desired electrical properties. Apart from electron irradiation induced defects [10,12], substrate charging has been suggested as a mechanism for the change in the conductivities of the irradiated SWCNTs [4,5]. To our knowledge no studies have shown conclusively whether either of these mechanisms or other mechanism is responsible for the transitions, nor is the mechanism by which low-energy electron irradiation produces defects in isolated or bundled SWCNTs well understood.…”

Origin of the Electric Property Change of a Single-Wall Carbon Nanotube Caused by Low-Energy Irradiation: Defects or Substrate Charging?

“…A moderate irradiation can convert the room temperature electric properties of a metallic SWNT to semiconducting [4]. An intensive irradiation finally makes a SWNT almost insulating [5][6][7][8]. The decreased conductivity with the irradiation, as well as the degraded Raman and PL spectra, can recover reversibly by annealing [1,3,6] or applying a high bias to the SWNTs [7,8].…”

“…Although the irradiation-induced conductivity decreases in a SWNT and its recovery have been experimentally well established [5][6][7][8], the origin of the conductivity decrease is still controversial. We have reported that the irradiation-induced physical property changes are caused by defects created by the irradiation (low-energy irradiation damage) [6].…”