Advanced Functional Materials

Cover image for Vol. 26 Issue 20

16_18/2006Cover Picture: Bilayer Organic–Inorganic Gate Dielectrics for High-Performance, Low-Voltage, Single-Walled Carbon Nanotube Thin-Film Transistors, Complementary Logic Gates, and p–n Diodes on Plastic Substrates (Adv. Funct. Mater. 18/2006)

Low-voltage, hysteresis-free, flexible thin-film-type electronic systems based on networks of single-walled carbon nanotubes and bilayer organic–inorganic nanodielectrics are detailed in work by Rogers and co-workers reported on p. 2355. The cover image shows a schematic array of such thin-film transistors (TFTs) on a plastic substrate. The structure of the bilayer nanodielectric, which consists of a film of HfO2 formed by atomic layer deposition and an ultrathin layer of epoxy formed by spin-casting, is also illustrated schematically.

High-capacitance bilayer dielectrics based on atomic-layer-deposited HfO2 and spin-cast epoxy are used with networks of single-walled carbon nanotubes (SWNTs) to enable low-voltage, hysteresis-free, and high-performance thin-film transistors (TFTs) on silicon and flexible plastic substrates. These HfO2–epoxy dielectrics exhibit excellent properties including mechanical flexibility, large capacitance (up to ca. 330 nF cm–2), and low leakage current (ca. 10–8 A cm–2); their low-temperature (ca. 150 °C) deposition makes them compatible with a range of plastic substrates. Analysis and measurements of these dielectrics as gate insulators in SWNT TFTs illustrate several attractive characteristics for this application. Their compatibility with polymers used for charge-transfer doping of SWNTs is also demonstrated through the fabrication of n-channel SWNT TFTs, low-voltage p–n diodes, and complementary logic gates.

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