Rubrene/CuInP2S6 organic/inorganic heterojunctions for ferroelectric organic transistor memory devices

Abstract

Ferroelectric organic field-effect transistor (Fe-OFET) memory devices exhibit low power consumption, low cost and good flexibility, which are indispensable to next generation flexible and wearable memory devices. However, up until the present, the ferroelectric materials used in Fe-OFETs have been limited to ferroelectric polymers, i.e. poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], and suffer from large surface roughness and high-risk of depolarization. This work integrates a new two-dimensional CuInP2S6 crystal into Fe-OFET, which can introduce excellent ferroelectric property due to its single crystalline smoothness and noncentrosymmetric crystal structure. Meanwhile, the high-mobility rubrene crystal is selected as the channel material to construct rubrene/CuInP2S6 organic/inorganic van der Waals heterojunctions. Associated with synergetic effect of single-crystalline nature of the heterojunction and atomically flat/defect-free interface, the memory devices possess a high programming speed of 0.5 s and long retention time of 104 s with a current ratio larger than 103. Furthermore, the performance of flexible devices is also demonstrated, including a programming/erase cycle of 1000 with a current on/off ratio approaching 103, data retention time of 104 s with a current on/off ratio of 103 and a current on/off ratio maintained at 102 even after 100 bending cycles under a bending radius of 25 mm, which are qualified for memory buffer usage or short-term data storage especially when they are integrated with other flexible electronics. The proposed configuration of memory transistors using organic/inorganic heterojunctions provides a rational design of device structure toward flexible Fe-OFET non-volatile memory applications.