Hafnium oxide layer-enhanced single-walled carbon nanotube field-effect transistor-based sensing platform.

Single-walled carbon nanotube-based field effect transistors (SWCNT-FETs) are ideal candidates for fabricating sensors and have been widely used for chemical sensing applications. SWCNT-FETs have low selectivity because of the environmentally sensitive electronic properties of SWCNTs, and SWCNT-FETs also show a high noise signal and poor sensitivity because of charge trapping from Si-OH hydration of the SiO/Si substrate on the SWCNTs. Herein, poly (4-vinylpyridine) (P4VP) was used for noncovalent attachment to SWCNTs and selective binding to copper ions (Cu). Importantly, the introduction of a hafnium-oxide (HfO) layer through atomic layer deposition (ALD) overcame the charge trapping by SiO hydration and remarkably decreased the interference signal. The sensitivity of the P4VP/SWCNT/HfO-FET sensor for Cu was 7.9 μA μM, which was approximately 100 times higher than that of the P4VP/SWCNT/SiO-FET sensor, and its limit of detection (LOD) was as low as 33 pmol L. Thus, the P4VP/SWCNT/HfO-FET sensor is a promising candidate for the development of Cu-selective sensors and can be designed for the large-scale manufacturing of custom-made sensors in the future.