Noise properties of carbon nanotube FETs with top-and side-gate geometries: Effect of gamma irradiation

We demonstrate field-effect transistors (FETs) fabricated on the basis of individual carbon nanotubes (CNTs) with top- and side-gate configurations using two different dielectric layers, SiO₂ and Al₂O₃. Transport properties of the FETs are investigated using noise spectroscopy before and after low-dose gamma irradiation treatment (10⁶ rad). A strong generation-recombination (GR) noise component observed before the treatment is used to identify several charge traps of two dielectric layers by their activation energy. In spite of reduced flicker noise level after gamma irradiation, the GR noise component almost disappears in the spectra after treatment. This indicates the reduction in the number of charge traps. We study the influence of the Schottky barriers at the metal-nanotube interface on the properties of FETs by analyzing the flicker noise component and identified the regime where the contact contribution is negligible and the conductivity is determined by the properties of CNT material.