Comparison of purity in single walled carbon nanotube gas detectors with Pd and Ti electrodes using low frequency noise techniques

Abstract

This work deals with oxide traps properties of single walled carbon nanotubes (SWCNTs) based gas sensors using Random telegraph signals (RTS) and low frequency (LF) noise techniques. RTS signals are two or more levels switching events that we observe measuring the drain current of transistors with Ti (RTS1) and Pd (RTS2) contacts. RTS noise is analyzed in time and frequency domains. Time domain analysis allows us to identifying slow traps (three traps) responsible to RTS noises (energetic position and cross capture section). These traps undetectable by other techniques, e.g. deep level transient spectroscopy (DLTS) technique, are localized in the gate oxide region. The spatial localization of the three traps in the SWCNT/SiO2 interface are determined using numerical simulations (yTrap1 ≈0.6nm, yTrap2 ≈0.9nm and yTrap3 ≈0.3nm). (RTS1) noise is attributed to trap1 and (RTS2) to traps 2 and 3. From RTS analysis in frequency domain, are able to extract the cut-off frequencies of a single trap even at very low frequencies (for RTS1 noise fc=10Hz (trap1) and for RTS2 noise fc1=4Hz (trap2), fc2=50Hz (trap 3)). These results are in good agreement with those obtained by analysis in time domain and confirm the localization of each trap from the SWCNT/SiO2 interface. This is the first time that this kind of studies is performed on CNTFETs used as gas sensors and gives us some interesting hints on the potential phenomena related to these new generation of carbon based nanomaterials based devices in the field of electronics.