The ability to form integrated circuits on flexible sheets of plastic enables attributes (for example conformal and flexible formats and lightweight and shock resistant construction) in electronic devices that are difficult or impossible to achieve with technologies that use semiconductor wafers or glass plates as substrates. Organic small-molecule and polymer-based materials represent the most widely explored types of semiconductors for such flexible circuitry. Although these materials and those that use films or nanostructures of inorganics have promise for certain applications, existing demonstrations of them in circuits on plastic indicate modest performance characteristics that might restrict the application possibilities. Here we report implementations of a comparatively high-performance carbon-based semiconductor consisting of sub-monolayer, random networks of single-walled carbon nanotubes to yield small- to medium-scale integrated digital circuits, composed of up to nearly 100 transistors on plastic substrates. Transistors in these integrated circuits have excellent properties: mobilities as high as 80 cm(2) V(-1) s(-1), subthreshold slopes as low as 140 m V dec(-1), operating voltages less than 5 V together with deterministic control over the threshold voltages, on/off ratios as high as 10(5), switching speeds in the kilohertz range even for coarse (approximately 100-microm) device geometries, and good mechanical flexibility-all with levels of uniformity and reproducibility that enable high-yield fabrication of integrated circuits. Theoretical calculations, in contexts ranging from heterogeneous percolative transport through the networks to compact models for the transistors to circuit level simulations, provide quantitative and predictive understanding of these systems. Taken together, these results suggest that sub-monolayer films of single-walled carbon nanotubes are attractive materials for flexible integrated circuits, with many potential areas of application in consumer and other areas of electronics.

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Abstract-Steep sub-threshold Interband Tunnel FETs (TFETs) are promising candidates for low supply voltage applications with higher switching performance than traditional CMOS. Unlike CMOS, TFETs exhibit uni-directional conduction due to their asymmetric source-drain architecture, and delayed output saturation characteristics. These unconventional characteristics of TFETs pose a challenge for providing good read/write noise margin characteristics in TFET SRAMs. We provide an analysis of 8T and 10T TFET SRAM cells, including Schmitt-Trigger (ST) based cells, to address these shortcomings. By benchmarking a variety of TFET-based SRAM cells, we show the utility of the Schmitt-Trigger feedback mechanism in improving the read/write noise margins, thus enabling ultra low-VCC operation for TFET SRAMs. We also propose a variation model for studying the impact of device-level variation on TFET SRAM cells. We show that the TFET ST SRAM cell has sufficient variation tolerance to operate at low-VCC, and is a very promising cell to achieve a VCC-min of 124mV. The TFET ST cell operating at its VCC-min provides a 1.2x reduction in dynamic energy and 13x reduction in leakage power compared to the best CMOS-based SRAM implementation operating at it's VCC-min, while giving better performance at the same time.

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