Mixed composite dielectric of high- κ oxide and organic polymer could be made by solution process to balance the dielectric property and flexibility 22, 23, 24, but owing to the strong propensity of phase segregation at nanoscale, complete coating of a uniform thin dielectric layer on CNTs at a large scale was found to be extremely challenging if not impossible, which therefore seriously limits the use of the solution methods for circuit fabrication. Organic polymer dielectrics have been attempted as a replacement 20, but the device performance is fairly limited owing to a low κ value of the polymers and a thick layer required to ensure the insulating property 21. However, CNT TFTs commonly have an Achilles’ heel at the gate dielectric, because the majority devices used brittle high- κ oxides (e.g., Al 2O 3 and HfO 2) as the gate dielectric and the oxides would break upon bending, resulting in current leakage 13, 15, 16, 17, 18, 19. Therefore, the flexible circuits built on ACNT TFTs can possibly enable many emerging applications in the ‘smart’ electronics and technologies. Owing to a fairly high carrier mobility together with superior mechanical flexibility and solution processability, ACNT TFTs have shown great promise for applications in flexible electronics 13, 14. This type of TFTs is also known as all-CNT (ACNT) TFTs. To this end, carbon nanotube (CNT) based TFTs have recently stood out for the intrinsic superior flexibility of CNTs 11, 12, and particularly, not only the TFT channels but also the source, drain, and gate electrodes as well as the interconnects can be made of CNTs. Therefore, it is highly desirable to have TFTs that are intrinsically flexible to constitute the circuits. Although it is possible to mitigate the flexibility issue at the circuit level by engineering the interconnects with sophisticated shapes, this type of design nevertheless trades off a significant portion of the circuit area to accommodate the large interconnects, thereby limiting the integration density of circuits 10. The rapid expansion of flexible electronics has accordingly imposed varieties of new demands and challenges on the performance of TFTs, such as real-time interactivity, high-strain stability, and integrable multifunctionality, but nevertheless, simultaneously achieving high electrical performance and mechanical performance remains a giant obstacle for flexible TFTs in general. In contrast to traditional microelectronics, flexible electronics are mainly built on thin-film transistors (TFTs) 5, which serve as the indispensable integrable elements for flexible analog and digital integrated circuits 5, 6, sensor networks 7, 8, and display backplanes 9. Many cutting-edge areas, such as medicine and healthcare 1, 2, perception and intelligent robots 3, and brain-machine interfaces 4, have intensively adopted the flexible electronics technology to dramatically expand their functionalities. Flexible wearable electronics constitute the key building blocks in these smart technologies, which closely connect the human body to the electronics nearby as well as over the world. The Internet of Things (IoT) and artificial intelligence has significantly facilitated our way of living by introducing many emerging ‘smart’ technologies, such as smart robots, smart home, smart city, and smart industries. Ultralow voltage (50 mV) operation is also feasible, which highlights the great promise for low-power applications. Particularly, the inverters exhibit a remarkably high gain of 342.5 and can be used as an analog amplifier for millivolt small signals. With this hybrid dielectric, high-performance all-CNT transistors and integrated circuits of inverters, ring oscillators, and logic gates are demonstrated. Herein, we show that a hybrid polyimide-Al 2O 3 material can serve as a good gate dielectric to realize truly intrinsic flexibility of transistors and circuits based on CNTs. However, the gate dielectric often has to adopt brittle oxides, which can seriously limit the device flexibility.

Carbon-nanotube (CNT)-based electronics are of great promise to this end for their intrinsic flexibility, high carrier mobility, and capability to synthesize as semiconducting or metallic to serve as the channels, electrodes, and interconnects of circuits. The advancement of Internet of Things has stimulated huge demands on low-voltage flexible electronics.

Al atomic radius