2 V bias with 10 ms duration. The mean value of current is 89.29 μA with the standard deviation of 0.155. The current ratio of low-resistance to high-resistance state in this device is about 22.85 (which varied in 20 to 40 range for various

devices). Besides the high retention time, the device also shows good endurance when continuous reading cycles with small pulse duration is applied. The retention characteristics are extrapolated to 104 s, and a stable behavior is foreseen in both states of the device. Figure 3 Retention characteristics. The memory device shows a stable low-resistance state with for 103 s (blue line). Tariquidar research buy After switching to the high-resistance state by applying a 1.2-V write pulse of 10 ms duration, stable current is observed again. The dashed lines are the interpolation to 104 s (red line). For the control sample without the BLG contact, the device shows higher conduction with random switching, hysteresis, and significant variation from device to device. We attribute this irregular behavior in our control sample to the atomically rough interface between Ni and C60, as well as the electromigration of Ni atoms across C60/Ni interface. The switching mechanism in the reported WORM memory device with the BLG contact is not clearly understood yet. However, we hypothesize

selleckchem that BLG prevents the electromigration of Ni atoms into C60 film, thus stabilizing the device behavior. The transport characteristics do not show ohmic or space-charge-limited conduction. Similar devices using C60 molecules have been reported to have rewritable switching characteristics – quite different from our observation [19, 20]. click here Moreover, multilayer graphene electrodes used in devices with PI:PCBM composite as active material have also been recently reported to have mafosfamide WORM memory behavior, whereas with the metallic electrodes, rewritable switching characteristics have been

reported [21]. Although the channel materials are different in the two experiments, the connection between the use of graphene and WORM features is noteworthy and needs to be explored further. Carbon nanotube-based contact [22] has also been explored to eliminate electromigration, however, we believe that graphene nanomembrane provides a better interface due to its 2D nature. Conclusions We have fabricated a molecular memory device with atomically smooth BLG contacts. Covering Ni film with BLG shields the channel from metal surface irregularities and also prevents the electromigration of Ni atoms into the C60 film. The device switches from a low-resistance to a high-resistance state, followed by hysteresis in the first sweep cycle. In the subsequent sweep cycles, the device remains in the high-resistance state and no hysteresis is observed, thus showing WORM memory behavior. The switching voltages vary in 0.8 to 1.2 V bias range for various devices with the high-resistance to low-resistance ratio in 20 to 40 range.