Abstract
A humidity sensor using suspended carbon nanotubes (CNTs) was fabricated using a low-temperature surface micromachining process. The CNTs were functionalized with carboxylic acid groups that facilitated the interaction of water vapor with the CNTs. The humidity sensor showed a response time of 12 s and a recovery time of 47 s, along with superior hysteresis and stable performance. The hysteresis curve area of the suspended structure is 3.6, a 3.2-fold reduction in comparison to the non-suspended structure. A comparative study between suspended and non-suspended devices highlights the advantages of using a suspended architecture.
Highlights
Carbon nanotubes (CNTs), first discovered by Iijima [1], are one of the most studied materials for gas sensing applications [2]
The inherent properties of CNTs, such as high surface area to volume ratio and a hollow structure, along with the ease of surface modification, have led to the use of both single- and multiwalled CNTs to detect a variety of gases with much success [3]
Most of the humidity sensors based on CNTs have been based on functionalized CNTs and have shown considerable promise for commercial usage
Summary
Carbon nanotubes (CNTs), first discovered by Iijima [1], are one of the most studied materials for gas sensing applications [2]. Fast response and recovery times and low hysteresis of a humidity sensor are important parameters to consider, and recovery performance during prolonged exposure to high humidity levels is of interest for sensors to be commercially deployed. These parameters are considered in this work for the proposed devices. The suspended CNTs showed near-zero hysteresis and better response and recovery times than non-suspended CNTs. the fabrication process proposed had a low temperature budget, making the sensors suitable for integration above integrated circuits. To further demonstrate the advantages of using a suspended architecture, the device performance is compared to a traditional non-suspended CNT device using the same fabrication process
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