Selective Chemistry-Based Separation of Semiconducting Single-Walled Carbon Nanotubes and Alignment of the Nanotube Array Network under Electric Field for Field-Effect Transistor Applications

Abstract

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are considered as a replacement for silicon in fieldeffect transistors (FETs), solar cells, logic circuits, and so forth, because of their outstanding electronic, optical, and mechanical properties. Herein, we have studied the reaction of pristine SWCNTs dispersed in a pluronic F-68 (PF-68) polymer solution with para-amino diphenylamine diazonium sulfate (PADDS) to separate nanotubes based on their metallicity. The preferential selectivity of the reactions was monitored by changes in the semiconducting (S 22 and S 33 ) and metallic (M 11 ) bands by ultraviolet−visible−near infrared spectroscopy. Metallic selectivity depended on the concentrations of PADDS, reaction time, and the solution pH. Furthermore, separation of pure s-SWCNTs was confirmed by Raman spectroscopy and Fourier-transform infrared spectroscopy. After the removal of metallic SWCNTs, direct current electric field was applied to the pure s-SWCNT solution, which effectively directed the nanotubes to align in one direction as nanotube arrays with a longer length and high density. After that, electrically aligned s-SWCNT solution was cast on a silicon substrate, and the length of the nanotube arrays was measured as ∼2 to ∼14 μm with an areal density of ∼2 to ∼20 tubes/μm of s-SWCNTs. Next, electrically aligned s-SWCNT arrays were deposited on the channel of the FET device by drop-casting. Field-emission scanning electron microscopy and electrical measurements have been carried out to test the performance of the aligned s-SWCNTs/FETs. The fabricated FETs with a channel length of 10 μm showed stable electrical properties with a field-effect mobility of 30.4 cm 2 /Vs and a log 10 (I on /I off ) current ratio of 3.96. We envisage that this new chemical-based separation method and electric field-assisted alignment could be useful to obtain a high-purity and aligned s-SWCNT array network for the fabrication of high-performance FETs to use in digital and analog electronics.

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“…MWCNTs exhibit enhanced electrical conductivity due to delocalized p electron through the sp 2 hybridized hollow carbon structure with variable chirality, improved thermal stability, and possess a higher surface area (>200 m 2 g −1 ). 36,37 The sp 2 hybridized smooth graphitic plane creates faster electron transport channels. However, because of the van der Waals force and p-p stacking interaction between the individual tubes, MWCNT has limited dispersion and coalesces the tube with surface defect.…”

Controllable self-cleaning FET self-assembled RNA-cleaving DNAzyme based DNA nanotree for culture-free Staphylococcus aureus detection

“…Single-walled carbon nanotubes (SWNTs) [ 23 ] are promising materials for use in both nanoelectronics and thin film devices, which can be used as a sensitive material but also as a conductive material depending on its chemical structure. Semiconducting SCNT (s-SWNT), which has mobility reaching 79,000 cm 2 V -1 s -1 [ 24 ], is considered to be among the most promising sensitive materials for field-effect transistors. Metallic SWNT (m-SWNT) has a conductivity approaching 10 5 S/cm with low resistance [ 25 ], and is suitable for application as conducting wires for field-effect transistors.…”