Evaluation of Influence of Substrate Planarization on the Uniformity of Flexible Carbon Nanotube Thin Film Transistors

Carbon nanotubes (CNTs) are one of the most promising semiconducting materials for flexible electronics due to their numerous advantages. However, the performance uniformity of flexible CNT thin film transistors (TFTs) still needs to be improved to advance this technology toward practical applications. This article carried out specific exploration of the effects of substrate roughness on deposited CNT thin film uniformity, which would further influence the performance variation of CNT TFTs. An efficient method of adopting a polyimide (PI) planarization layer was used to smooth the flexible substrate, enabling highly uniform CNT deposition. Flexible CNT TFTs were fabricated to verify the effectiveness of substrate planarization with improved performance uniformity of 400 ± 60 mV in threshold voltage and 5.44 ± 0.1 decades in current ON– OFF ratio, which are superior than the previously reported flexible CNT TFTs. Inverters were also constructed with homogeneous output voltage and switching threshold voltage to verify the uniformity at circuit level. This approach promotes the uniformity of CNT TFTs on flexible substrate, which would provide great potential for flexible CNT based electronics in practical applications that need large scale device integration.