Mechanical flexibility of zinc oxide thin-film transistors prepared by transfer printing method

In the present study, we demonstrate the performance of Zinc oxide thin film transistors (ZnO TFTs) array subjected to the strain under high bending test and the reliability of TFTs was confirmed for the bending fatigue test of 2000 cycles. Initially, ZnO TFTs were fabricated on Si substrate and subsequently transferred on flexible PET substrate using transfer printing process. It was observed that when the bending radius reached < 11 mm then cracks start to initiate first at SiO ₂ bridges, acting as interconnecting layers among individual TFT. Whatever the strain is applied to the devices, it is almost equivalently adopted by the SiO ₂ bridges, as they are relatively weak compared to rest of the part. The initial cracking of destructed SiO ₂ bridge leads to the secondary cracks to the ITO electrodes upon further increment of bending radius. Numerical simulation suggested that the strain of SiO ₂ layer reached to fracture level of 0.55% which was concentrated at the edge of SiO ₂ bridge layer. It also suggests that the round shape of SiO ₂ bridge can be more fruitful to compensate the stress concentration and to prevent failure of device.