Carbon nanotube field effect transistor measurements in vacuum

Abstract

Three terminal measurements on a carbon nanotube field effect transistor (CNTFET) were carried out in high vacuum and the ambient, and its performance compared. The on-off current ratio, ION/IOFF, were 102 and 105 for devices operated in high vacuum and in ambient air, respectively. Here, we show that the conversion of p-type to ambipolar behavior may largely be attributed to the O2 in ambient doping the single walled carbon nanotubes (SWCNTs) in the active channel which consists of bundles of SWCNTs. Switching behaviour of these devices, with respect to constituent types of SWCNTs in the bundles will be discussed

Hybrid Carbon Nanotube Networks as Efficient Hole Extraction Layers for Organic Photovoltaics

“…Despite this, the weak ambipolar nature leads to relatively low I on / I off ratios of ∼10 3 for negative gate voltages. It is noted that similar observations for preferential hole transport have been made for carbon nanotube FETs measured in air, where hole doping due to exposure to O 2 suppresses the n-type behavior (and hence the ambipolar nature) of the device . As the transport measurements have been carried out in N 2 environment, the observed preferential hole transport in the nanohybrids is attributed to the hole doping of the s-SWNTs due to charge transfer interactions between rr-P3HT and the nanotubes.…”

“…This is due to the tunnelling of electrons from the contacts to the nanotubes under positive gate voltages 35 , especially when measured in vacuum. 37 As expected for Schottky barrier s-SWNT transistors, the transfer characteristics indicates a suppressed ambipolar charge transport with an electron transport that is 2-3 orders of magnitude lower in comparison to that of hole transport in the device. Despite this, the weak ambipolar nature leads to relatively low I on /I off ratios of ~10 3 for negative gate voltages.…”

“…It is noted that similar observations for preferential hole transport have been made for carbon nanotube FETs measured in air, where hole doping due to exposure to O 2 suppresses the n-type behavior (and hence the ambipolar nature) of the device. 37 As the transport measurements have been carried out in N 2 environment, the observed preferential hole transport in the nanohybrids is attributed to the hole doping of the s-SWNTs due to charge transfer interactions between rr-P3HT and the nanotubes. The measured lateral in-plane transport values for the nanohybrid structures are observed to be comparable to those reported in the self-organized nanotube networks in SiO 2 by Bao et al 38 Nanohybrids as a Hole Extraction Layer in OPVs.…”

“…However, the formation of a Schottky contact to nanotubes is considered to be detrimental to device performance by affecting the charge injection and hence the ballistic transport properties, as well as leading to ambipolar transport characteristics. This is due to the tunneling of electrons from the contacts to the nanotubes under positive gate voltages, especially when measured in vacuum …”

Temperature dependent separation of metallic and semiconducting carbon nanotubes using gel agarose chromatography

“…The transfer characteristic of Dev-1 shows asymmetric ambipolar behavior that is p-type dominant, which can be attributed to the intrinsic properties of the DIPS-SWNTs source. SWNTs synthesized via the DIPS method has been shown to generally demonstrate ambipolar behavior when exploited as the active channel of a transistor [112], whilst SWNTs in general exhibit p-type behavior in air [5].…”