Abstract
Biosensors based on liquid-gated carbon nanotubes field-effect transistors (LG-CNTFETs) have attracted considerable attention, as they offer high sensitivity and selectivity; quick response and label-free detection. However, their practical applications are limited due to the numerous fabrication challenges including resist-based lithography, in which after the lithography process, the resist leaves trace level contaminations over the CNTs that affect the performance of the fabricated biosensors. Here, we report the realization of LG-CNTFET devices using silicon shadow mask-based chemical-free lithography process on a 3-in. silicon wafer, yielding 21 sensor chips. Each sensor chip consists of 3 × 3 array of LG-CNTFET devices. Field emission scanning electron microscope (FESEM) and Raman mapping confirm the isolation of devices within the array chip having 9 individual devices. A reference electrode (Ag/AgCl) is used to demonstrate the uniformity of sensing performances among the fabricated LG-CNTFET devices in an array using different KCl molar solutions. The average threshold voltage (Vth) for all 9 devices varies from 0.46 to 0.19 V for 0.1 mM to 1 M KCl concentration range. This developed chemical-free process of LG-CNTFET array fabrication is simple, inexpensive, rapid having a commercial scope and thus opens a new realm of scalable realization of various biosensors.
Highlights
Biosensors based on liquid-gated carbon nanotubes field-effect transistors (LG-CNTFETs) have attracted considerable attention, as they offer high sensitivity and selectivity; quick response and label-free detection
As-synthesized single-walled Carbon nanotubes (CNTs) (SWNTs) consist of a mixture of semiconducting (s-) and metallic (m-) nanotubes. The use of this mixture will yield to the variations in device-todevice performance and m-SWNTs degrade the performance of the electronic devices
The resistances of all 189 devices in 21 chips have been measured to assess the uniformity of spray-coated s-SWNTs on the 3-in. substrate
Summary
Biosensors based on liquid-gated carbon nanotubes field-effect transistors (LG-CNTFETs) have attracted considerable attention, as they offer high sensitivity and selectivity; quick response and label-free detection. The average threshold voltage (Vth) for all 9 devices varies from 0.46 to 0.19 V for 0.1 mM to 1 M KCl concentration range This developed chemical-free process of LG-CNTFET array fabrication is simple, inexpensive, rapid having a commercial scope and opens a new realm of scalable realization of various biosensors. A silicon shadow mask with openings is fabricated using silicon bulk-micromachining and successfully aligned with the predefined source-drain electrode structures followed by optimized spray coating process to fabricate an array of LG-CNTFET devices. This process is chemical-free, economic, rapid, ease in use and scalable for commercial production of LG-CNTFET device array as a chemical/biochemical sensing platform. The sensing performance of the fabricated LG-CNTFET biosensing platform with 0.1 mM to 1 M range of KCl concentrations confirms the consistency and uniformity among the complete array of devices
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