Investigation of the humidity effect on the electrical properties of single-walled carbon nanotube transistors

Abstract

We investigated the effect of humidity on the electrical transport properties of single-walled carbon nanotube field effect transistors (SWNT-FETs). Water molecules are found to behave as electron donors to the nanotube: Current through the p-type carbon nanotube device is found to decrease under a modest humidity, and starts to increase as the humidity increases over 65%, which is believed to be due to the opening of electron channels. Through first principles calculations based on the density functional theory, we found that water molecules can donate electrons to the carbon nanotube. Moreover, a hydrogen-bonded water monolayer will be formed around the nanotube at fully covered conditions. We suggest that this result could provide a systematic understanding of the humidity effect on SWNT-FETs, which has been believed to be essential in the development of nanotube-based sensors.

Charge Doping in Water-Adsorbed Carbon Nanotubes

“…Experimental investigations of the effect of water vapour on the conductivity of mats and fibres of CNTs have reached contradictory conclusions with both increases [8][9][10][11][12] and decreases [13][14][15] in conductivity observed. The lack of agreement may be attributable to an abundance of factors, including the CNT sample composition and purity, the presence of impurities and their composition, contact resistances with external electrodes and between the CNTs themselves, and the alignment and connectivity of CNTs in the mat/fibre network.…”

Carbon nanotube-based nano-fluidic devices

“…[117][118][119][120] Internal wetting produces exactly the opposite result: the threshold moves to more positive gate bias and the hysteresis decreases.…”

“…V ds = 0.8V for both (a) and (b). (c) I ds time traces during adding water into the reservoirs for both unopened and opened tubes at V ds = 0.8 V and V gs = 10 V. 124 Studies of external wetting [117][118][119][120] have been carried out using a window opened in dielectric material that covers the metallic contacts (Figure 6.5).…”

“…115,116 Wetting of the outside of SWCNT-FETs by water changes their hysteresis and shifts their threshold gate voltage (V th ). [117][118][119][120] The resistivity of SWCNT mats falls when they are wetted (possibly both inside and outside) 104,121 but these results are difficult to interpret in terms of the response of individual SWCNTs. Thus, we have used our new devices, in which just one SWCNT connects two fluid reservoirs to compare the effects of external and internal wetting on SWCNT-FETs.…”

Carbon nanotube‐sensor‐integrated microfluidic platform for real‐time chemical concentration detection

“…CNT sensors provide high sensitivity, low power, and portable tools for in situ chemical analysis. So far, semiconducting sensors, normally constructed in transistor or field-effect transistor form with CNTs distributed on thin film [10][11][12][13][14][15], are the most studied application of CNTs for detecting chemical gases. When the gas molecules are absorbed on the CNTs, there will be charge transfer between the CNT sensor and the molecules; thus the conductance of the sensor is changed.…”