Carbon nanotube transistors exhibiting high on-state conductance, carrier mobilities, and on−off ratios are achieved using polymer electrolytes as gate media. Nearly ideal gate efficiencies allow operation at very small voltages without the commonly observed problem of hysteresis in back-gated nanotube and nanowire transistors. By varying the electron donating and accepting ability of the chemical groups of the host polymer, unipolar p or n devices or ambipolar transistors that are stable at room temperature in air are also shown to be easily fabricated. With simple methods such as spin casting of polymer films, high-performance polymer electrolyte-gated nanotube transistors may provide useful components for and an alternative route to developing hybrid electronics.

High performance single-walled carbon nanotube field effect transistors (SWCNT-FETs) fabricated with thin atomic layer deposited (ALD) Al2O3 as gate dielectrics and passivation layer are demonstrated. A 1.5μm gate-length SWCNT-FETs with 15nm thick Al2O3 insulator shows a gate leakage current below 10−11A at −2.5V<Vg<+7V, a subthreshold swing of S∼105mV∕decade, and a maximum on current of −12μA at a reverse gate bias of −1V. Lack of hysteresis in IV characteristics and low low frequency noise indicate high quality oxide-nanotube interface achieved utilizing ALD Al2O3 as gate dielectrics and passivation layer.

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Carbon nanotube electrochemical transistors integrated with microfluidic channels are utilized to examine the effects of aqueous electrolyte solutions on the electron-transport properties of single isolated carbon nanotubes. In particular, pH and concentration of supporting inert electrolytes are examined. A systematic threshold voltage shift with pH is observed while the transconductance and subthreshold swing remain independent of pH and concentration. Decreasing pH leads to a negative shift of the threshold voltage, indicating that protonation does not lead to hole doping. Changing the type of contact metal does not alter the observed pH response. The pH-dependent charging of SiO2 substrate is ruled out as the origin based on measurements with suspended nanotube transistors. Increasing the ionic strength leads to reduced pH response. Contributions from possible surface chargeable chemical groups are considered.

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