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Current-voltage curves at (dashed lines) and at (solid lines) for an array of TOPO-capped CdSe NCs in the dark and during excitation with green laser. The voltage sweep rate is . Upper inset: Transmission electron micrograph of the NC film. The scale bar is . Lower inset: Device schematic; long electrodes are separated by . The back gate is grounded.
Voltage (dashed line) and current (solid line) vs time for two consecutive memory cycles for the device in Fig. 1. The numbered steps are: (1) write (, dark), (2) wait (, dark), (3) read (, dark), and (4) erase (, photoexcitation) or (, dark). In this example, and during and . In Step 4, NCs were photoexcited. and are currents at time after the start of the write and read steps, respectively.
(a) vs the transient number, i.e., the number of the negative voltage steps, , for 1000 consecutive memory cycles. is the current at time after the application of the negative voltage step. and correspond to even and odd values of , respectively (see Fig. 2); , , , , and photoexcitation was used to erase. (b) vs the transient number, , for consecutive memory cycles modified to have nine read steps per cycle; , , , and positive voltage was used to erase. Inset: Voltage vs time for one modified memory cycle ( to 9). (c) The average value , calculated over consecutive iterations, vs for positive voltage erasing (circles) and photoexcitation erasing (squares).
, the current at time after the application of the negative voltage step vs the transient number, , for consecutive memory cycles with laser resetting (Fig. 2); changes every ten cycles from (triangles), to (squares), (circles), and (diamonds). After ten memory cycles, is set back to and the entire 40-step sequence is repeated; , , and . The first three repetitions of these 40-step sequences are shown. and correspond to even and odd values of , respectively (see Fig. 2). In one 40-step sequence increases by 80. Inset: vs the transient number, , for repetitions of 40-step sequences .
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