ABSTRACT
We report on the influence of low gamma irradiation (10(4) Gy) on the noise properties of individual carbon nanotube (CNT) field-effect transistors (FETs) with different gate configurations and two different dielectric layers, SiO2 and Al2O3. Before treatment, strong generation-recombination (GR) noise components are observed. These data are used to identify several charge traps related to dielectric layers of the FETs by determining their activation energy. Investigation of samples with a single SiO2 dielectric layer as well as with two dielectric layers allows us to separate traps for each of the two dielectric layers. We reveal that each charge trap level observed in the side gate operation splits into two levels in top gate operation due to a different potential profile along the CNT channel. After gamma irradiation, only reduced flicker noise is registered in the noise spectra, which indicates a decrease of the number of charge traps. The mobility, which is estimated to be larger than 2 × 10(4) cm(2) V(-1) s(-1) at room temperature, decreases only slightly after radiation treatment, demonstrating high radiation hardness of the CNTs. Finally, we study the influence of Schottky barriers at the metal-nanotube interface on the transport properties of FETs, analyzing the behavior of the flicker noise component.
ABSTRACT
We report experimental results for the changes in conductivity of single-wall carbon nanotube bundles when irradiated by (60)Co γ-rays in various environments. In the current study the samples investigated were irradiated in hermetic cells, either evacuated (0.1 Pa) or filled with hydrogen or deuterium at atmospheric pressure. In situ measurements of the resistance change as a function of irradiation dose at room temperature are presented. It was found that, for all irradiation conditions, the normalized resistance versus irradiation dose demonstrates a logarithmic behaviour. A phenomenological model for the observed dependence is derived. The current-voltage characteristics of the irradiated samples were measured in the temperature range from 4.5 to 300 K using short (10 ns) electric pulses, and the results demonstrate a scaling behaviour. This scaling occurs in the universal coordinates that correspond to the Tomonaga-Luttinger liquid concept. Our results confirm the existence of the Tomonaga-Luttinger liquid phase up to room temperature in carbon nanotubes after γ-irradiation to a dose of 5 × 10(7) rad in vacuum, 1.7 × 10(7) rad in hydrogen and 1.24 × 10(8) rad in deuterium.
