Single-Walled Carbon Nanotube Network Field Effect Transistor as a Humidity Sensor

Abstract

Single-walled carbon nanotube network field effect transistors were fabricated and studied as humidity sensors. Sensing responses were altered by changing the gate voltage. At the open channel state (negative gate voltage), humidity pulse resulted in the decrease of the source-drain current, and,vice versa, the increase in the source-drain current was observed at the positive gate voltage. This effect was explained by the electron-donating nature of water molecules. The operation speed and signal intensity was found to be dependent on the gate voltage polarity. The positive or negative change in current with humidity pulse at zero-gate voltage was found to depend on the previous state of the gate electrode (positive or negative voltage, respectively). Those characteristics were explained by the charge traps in the gate dielectric altering the effective gate voltage, which influenced the operation of field effect transistor.

Wavelength-dependent photoconductivity of single-walled carbon nanotube layers

“…The resistance change is then limited by the slow dynamics of oxygen and water desorption, affecting the doping of the SWCNT network. 46 At longer wavelengths (633 nm and 785 nm), the total absorbance is smaller which results in lower resistance changes. However, absorbance peaks due to electronic transitions in SWCNTs become relevant and the fast jump of the resistance can be related to the generation of free charge carriers.…”

Suspended Carbon Nanotubes for Humidity Sensing

“…However, few works have investigated single-walled nanotubes for humidity sensing. For instance, Mudimela et al [ 17 ] fabricated a humidity sensor based on networks of single-walled carbon nanotubes Field Effect Transistors (FETs). More recently, Zhou et al [ 18 ] developed a textile-based humidity sensor based on Poly vinyl alcohol (PVA) functionalized single-walled nanotubes with a response time of 40 s. Carboxylic acid functionalized single-walled nanotube networks were used on a cellulose paper template to sense humidity by Han et al [ 19 ] with a fast response time of about 6 s. All the above-mentioned works have used either single or a network of substrate bound carbon nanotubes.…”

Low-Hysteresis and Fast Response Time Humidity Sensors Using Suspended Functionalized Carbon Nanotubes

“…Yeow et al [14] used MWCNTs deposited on a stainless-steel substrate to fabricate a capacitive humidity sensor with a response time of 75 s. An MWCNTs-based humidity sensor was studied using different testing frequencies (AC current) with a response time of 16 s [15]. Researchers have also used single-walled CNTs to detect humidity [16]. However, most of the works mentioned above focus on the hysteresis performance of the proposed sensors.…”