30 research outputs found
Low-frequency Noise in Individual Carbon Nanotube Field-Effect Transistors with Top, Side and Back Gate Configurations: Effect of Gamma Irradiation
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
2x10^4 cm2V-1s-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.Comment: 19 pages, 9 figures, 1 table, accepted for publication in
"Nanotechnology" journa
Switchable Coupling of Vibrations to Two-Electron Carbon-Nanotube Quantum Dot States
We report transport measurements on a quantum dot in a partly suspended
carbon nanotube. Electrostatic tuning allows us to modify and even switch 'on'
and 'off' the coupling to the quantized stretching vibration across several
charge states. The magnetic-field dependence indicates that only the
two-electron spin-triplet excited state couples to the mechanical motion,
indicating mechanical coupling to both the valley degree of freedom and the
exchange interaction, in contrast to standard models