Transparent Nanoscale Polyimide Gate Dielectric for Highly Flexible Electronics

Abstract Transparent and solution‐processable nanoscale polyimide (NPI) films less than 100 nm thick and their applications as flexible gate dielectrics for 2D‐materials‐based transistor devices are reported. Stable electrical performances of NPI dielectric under high tensile strains up to 10% are demonstrated by in situ bending experiments. A welcome benefit of the NPI nanoscale thickness is that the optical transparency is improved over 84% across the visible spectrum compared to conventional thick polyimide, indicating suitability for transparent electronics, such as displays and sensors. Prototypical 2D active materials, molybdenum disulfide (MoS 2 ), and graphene using NPI gate dielectric show outstanding thin‐film transistors (TFTs) properties comparable to performances of similar devices using atomic layer deposition (ALD) gate dielectrics. For instance, MoS 2 FETs with NPI dielectric affords maximum field‐effect mobility of 30 cm 2 V −1 s −1 and ON/OFF current ratio >10 7 . Graphene FETs (GFETs), fabricated with NPI dielectric, also show DC and radio frequency (RF) performances comparable to similar devices with high‐κ dielectrics, such as maximum carrier mobility of ≈5170 cm 2 V −1 s −1 . An extrinsic cutoff frequency ≈6.5 GHz is achieved, which reveals that NPI is also a suitable dielectric for flexible RF TFTs for wireless communication systems.