Polymer-Sorted
Semiconducting Carbon Nanotube Networks for High-Performance Ambipolar
Field-Effect Transistors
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Abstract
Efficient selection of semiconducting
single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples
is crucial for their application as printable and flexible semiconductors
in field-effect transistors (FETs). In this study, we use atactic
poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative
with asymmetric side-chains, for the selective dispersion of semiconducting
SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs.
Lowering the molecular weight of the dispersing polymer leads to a
significant improvement of selectivity. Combining dense semiconducting
SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide
hybrid dielectric enables transistors with balanced ambipolar, contact
resistance-corrected mobilities of up to 50 cm<sup>2</sup>·V<sup>–1</sup>·s<sup>–1</sup>, low ohmic contact resistance,
steep subthreshold swings (0.12–0.14 V/dec) and high on/off
ratios (10<sup>6</sup>) even for short channel lengths (<10 μm).
These FETs operate at low voltages (<3 V) and show almost no current
hysteresis. The resulting ambipolar complementary-like inverters exhibit
gains up to 61