Fig. 12. CNT TFTs and ICs on flexible substrate. a) Photograph of fabricated devices on a flexible and transparent PEN substrate. b) Schematic cross section of a bottom gate TFT on PEN substrate with Al2O3 gate insulator. c) Transfer characteristics of a typical TFT with =100 Ојm at =-0.5 V, =100 Ојm. d) Input-output and gain characteristics of an inverter. Insets show the optical micrograph, circuit diagram and symbol of the inverter. e, f) Optical micrograph and circuit diagram of a 21-stage ring oscillator. g) Output characteristics of the ring oscillator with oscillation frequency of 2.0 kHz at =-4 V. h) Mobility and on/off ratio. Comparison between our 36 CNT TFTs with other representative TFTs based on CNT network, amorphous-Si, polycrystalline Si, ZnO-based semiconductors, and organic materials.