Fig. 2: Device characterization results.
a Representative I–V curves, measured with quasi-static DC voltage sweeps, for the 36 formed devices of the 6 × 6 subarrays located in the center of the crossbar. For clarity, the curve for one particular device is highlighted. b Retention results for 10 different devices with data for each device shown with a specific color. The tests for each device are performed 9 times with randomly chosen initial conductance. The evolution of the conductance was measured at 400 s intervals while continuously baking the crossbar circuit at 100 °C. c The standard deviation of the absolute conductance change normalized to Gmax = 62.5 µS, i.e., 100% × |Ginitial − Gfinal|/Gmax, as a function of the time interval for several ranges of initial conductances. Similar to panel b, the top axis corresponds to the measured retention data at 100 °C for 500 devices, with each device tested at 6 different initial states, while the bottom axis shows extrapolated results. For panels b and c, the bottom axes show extrapolated time at room temperature (RT) assuming 1.1 eV activation energy (see “Methods” section for details). d The switching endurance results for a crossbar device. The data are obtained by repeatedly applying alternative polarity sequences of 1-ms voltage pulses. The absolute amplitude of pulse in each sequence is initially 0.8 V and then ramped up with 0.1 V steps until the device reaches the extreme (i.e., on or off) state. Inset is a zoomed-in portion of the main panel, showing typical continuous switching during the endurance test. The device is switched about 105 times between its extreme states during the experiment. e Measured evolution of conductance upon application of increasing amplitude voltage pulses. All parameters of the utilized pulse sequences are similar to those shown in Fig. 3c inset, except for the 50 mV incremental step. f–h Extracted statistics of switching threshold voltages, defined as the smallest absolute voltage at which device conductance, measured at 0.25 V, change by 20%, shown as (f) histogram and (g, h) voltage maps for (g) set and (h) reset transitions. The conductances are measured at 0.1 V for panels b–d.
