(Invited) Etching of Surfactant from Solution-Processed, Type-Separated Carbon Nanotubes and Impact on Device Behavior

Semiconducting single-walled carbon nanotubes (SWCNTs) have great potential for use in electronic and optoelectronic devices.  However, methods for synthesizing SWCNTs produce a mixture of metallic and semiconducting materials requiring additional processing to separate by electronic type. Purification and enrichment of the semiconducting fraction is readily achieved using centrifugation of aqueous suspensions of SWCNTs with the help of surfactants, but this leaves residual surfactant on the SWCNT surface that can impact their electronic and optical properties. Here, we present a detailed study of the sodium taurodeoxycholate (STDC) surfactant removal process during vacuum annealing and show that it occurs through fractionation of the surfactant and that complete removal requires exceedingly high temperatures, indicating strong binding to the SWCNTs. We then present an approach based on air oxidation and mild annealing to completely remove the surfactant while maintaining the SWCNT properties. Using this approach, we compare single-SWCNT electronic devices with and without STDC and show that despite the very strong surfactant binding it does not affect device performance substantially.