Flexible multilevel resistive memory with controlled charge trap B- and N-doped carbon nanotubes

B- and N-doped carbon nanotubes (CNTs) with controlled workfunctions were successfully employed as charge trap materials for solution processable, mechanically flexible, multilevel switching resistive memory. B- and N-doping systematically controlled the charge trap level and dispersibility of CNTs in polystyrene matrix. Consequently, doped CNT device demonstrated greatly enhanced nonvolatile memory performance (ON-OFF ratio >10(2), endurance cycle >10(2), retention time >10(5)) compared to undoped CNT device. More significantly, the device employing both B- and N-doped CNTs with different charge trap levels exhibited multilevel resistive switching with a discrete and stable intermediate state. Charge trapping materials with different energy levels offer a novel design scheme for solution processable multilevel memory.