Electronically Pure Single Chirality Semiconducting Single-Walled Carbon Nanotube for Large Scale Electronic Devices
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Introduction Single semiconducting single-walled carbon nanotube (SWCNT) field effect transistors (FETs) have been reported to be the appropriate replacement for silicon FETs.1 In another side, thin film transistors constructed on bulky semiconducting SWCNTs are widely investigated.2 These reported s-SWCNT TFTs suffer from large current leakage and the variation of electronic properties due to the existence of metallic species and widely distributed diameters.3 Recently, we reported electronically pure single chirality semiconducting SWCNT ink with uniform diameter.4 The SWCNT thin films deposited from this solution were electrically characterized as electronically pure by exhibiting non-linear current-to-bias curves in Schottky diode and femto ampere off-current in thin film transistors (TFTs).4 Results and Discussion HiPCO SWCNTs The electronically pure single-chirality semiconducting SWCNT inks were extracted from the raw SWCNTs produced by high pressure CO conversion method (HiPCO).5 HiPCO SWCNTs are the only carbon nanotube sources to be separated out single-chirality species using different separation technologies like density gradient ultracentrifugation (DGU),6 gel chromatography7,8 and aqueous two phase partitioning.9 HiPCO SWCNTs have fewer defects that can stand for harsh mechanical ultrasonication, superior to chemical vapor deposition (CVD) SWCNTs and CoMo catalyzed (CoMoCAT) SWCNTs. The relative small diameters of HiPCO SWCNTs are more facilely differentiated in media than large diameter SWCNTs produced via arc discharge method or laser ablation method. More importantly, HiPCO SWCNTs were produced by simultaneously injecting catalyst precursors and carbon sources.5 Therefore, HiPCO SWCNTs can be continuously produced without the need to deposit catalysts. The consumed carbon sources are CO that is industrial waste gas. This will benefit for the reduction of global warming. Based on these facts, the production of HiPCO SWCNTs can scale-up and the cost of HiPCO SWCNTs can be even cheaper than multi-walled carbon nanotubes (MWCNTs). Single Chirality (6,5) HiPCO SWCNT Ink After HiPCO SWCNTs were dispersed in aqueous solution under the assistance of sodium dodecyl sulfate (SDS) and sodium cholate (SC) using tip ultrasonication, the SWCNT bundles were precipitated by ultra-speed centrifugation to give rise to well-dispersed single SWCNTs showing distinguishing absorption, luminescence and Raman features.10-12 Using the concentration gradients of SDS, SC and sodium deoxycholate (DOC), the well-dispersed SWCNTs adsorbed on gel column can be washing down selectively to generate different single-chirality SWCNTs like (7,3), (6,4), (6,5), (7,5), (8,3), (8,4), (7,6), (8,6), (9,4), (10,2),
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