Comprehensive Study on High Purity Semiconducting Carbon Nanotube Extraction

Abstract

Carbon nanotubes (CNTs) are a rapidly maturing emerging technology for next‐generation energy‐efficient digital Very‐Large‐Scale‐Integrated (VLSI) systems. However, a major remaining challenge facing CNT field‐effect transistors (CNFETs) are metallic CNTs, causing incorrect logic functionality and increased leakage power. As no CNT synthesis technique demonstrates a reliable path toward manufacturing 99.99% semiconducting CNTs (s‐CNT; required purity for VLSI systems), significant work focuses on solution‐based sorting of CNTs (selectively removing metallic CNTs post‐synthesis). Yet, there lacks both well‐controlled comparisons carefully optimizing key processing parameters simultaneously (CNT synthesis sources, polymer additive used for selective sorting, etc.), as well as statistically significant electrical transistor characterization sample sizes to form concrete conclusions. Here, >90 000 CNFETs (totaling >90 million CNTs) are fabricated and characterized to demonstrate the following key advances: 1) systematic exploration of the impact of different combinations of CNT synthesis sources and polymer additives on the electrical performance of transistors (analyzing on‐current, off‐current, on off ratio, and threshold voltage) to find the best combination, 2) how the optimization and choice of the CNT source can be decoupled from that of the polymer, and 3) an optimal CNT solution that achieves >99.99% s‐CNT purity using electrical measurements, meeting the requirement for VLSI systems.

Sequential Doping of Carbon Nanotube Wrapped by Conjugated Polymer for Highly Conductive Platform and Thermoelectric Application

“…In PIDF-BT@SWCNT, Columbic interactions formed by charge transfer between PIDF-BT and CNT are expected in addition to the π-π interactions known as the driving force for forming polymer-wrapped CNT. [30,31] In the case of doped PIDF-BT@SWCNT, in addition to the interaction between Figure 3. X-ray photoelectron spectroscopy (XPS) analysis of a) PIDF-BT, b)PIDF-BT@SWCNT, c) F4TCNT-doped PIDF-BT@SWCNT, and d) AuCl 3doped PIDF-BT@SWCNT at the binding energies of the C, N, and S atoms.…”

“…Indeed, CP-wrapped CNTs provide a mobility over 20 cm 2 V À1 s À1 , significantly higher than conventional CPs and offers exclusively semiconducting properties. [28][29][30][31] Although studies related to CP-wrapped CNTs have primarily centered on enhancing their semiconductor properties, the electrical properties could be tailored by adjusting the applied CPs. In particular, CP-wrapped CNTs prepared using CP with high doping ability are expected to be excellent conductive platforms through molecular doping due to the high mobility of CNTs and abundant charge carriers generated by CP doping.…”

Mixed‐Solvent Engineering as a Way around the Trade‐Off between Yield and Purity of (7,3) Single‐Walled Carbon Nanotubes Obtained Using Conjugated Polymer Extraction

“…[ 10,11 ] This is a very convenient approach as it produces suspensions of several SWCNT types, which can be directly deposited on many substrates due to the high volatility of typically employed organic solvents. Moreover, in many cases, CPE is considered the gold standard due to its far greater metallic nanotube removal efficiency, [ 12,13 ] better film‐forming properties of organic dispersions, [ 14 ] and higher performance of the resulting nanocircuits. [ 15,16 ] Unfortunately, such an approach currently provides a much smaller selection of isolable monochiral SWCNTs compared with the differentiation of SWCNTs in aqueous media ( Figure a).…”

Filled carbon-nanotube heterostructures: from synthesis to application

“…For single-walled carbon nanotubes (SWCNTs), the nanotube band structure is determined by the nanotube radius and chirality, which can be either metallic or semiconductor [7] . Using a SWCNT as the gate and molybdenum disulfide (MoS 2 ) as channel materials, a one-nanometer physical gate length transistor with a subthreshold swing of ~65 mV dev -1 at 298 K was achieved, breaking the five-nanometer-limitation of Si technology [8] . Furthermore, as separation methods for high-purity semiconductor single-walled carbon nanotube (s-SWCNT, > 99.99%) [9] have matured, highperformance high-density arrays s-SWCNT field effect transistors have been developed [10] , positioning s-SWCNTs as the candidate elements for the manufacture of next-generation electronic devices.…”