Ultra-thin flexible solid-gated graphene field-effect transistors fabricated using laser lift-off

The advancement of ultra-thin graphene field-effect transistors (GFET) is essential for the realization of high-performance flexible electronics in applications such as biointerfaces, wearable devices, and soft robotics. In this study, a wafer-scale fabrication method is developed, combining spin-coated polyimide substrates with standard microfabrication and laser lift-off techniques to produce GFET arrays on 5 μm-thick flexible films. This approach overcomes challenges associated with handling and exfoliating ultra-thin substrates, achieving a device density of 80 devices cm⁻² and a yield of 79%, surpassing previously reported values. The fabricated devices exhibit balanced ambipolar transport with electron and hole mobilities of approximately 279 cm² V⁻¹ s⁻¹, and retain over 90% of their initial mobility after 2000 bending cycles. Field-effect characteristics are preserved under bending radii down to 5 mm, demonstrating notable mechanical robustness for solid-gated flexible GFETs. Strain sensing performance is evaluated, yielding a gauge factor of 430 and a minimum detectable strain of 0.005%. Compared with commercial metal strain gauges, the devices display approximately eightfold greater sensitivity and maintain stable responses during repeated deformation cycles. These findings provide a robust fabrication platform for ultra-thin GFETs, facilitating their integration into flexible electronic systems that demand high sensitivity, mechanical durability, and conformability.