Figure 1. Geometry and electrical performance of the Ta/HfO₂/Pt cross point memristor.

(a) TEM cross-section view of the Ta/HfO₂/Pt device. The inset shows an optical top-view image of the device (scale bar: 50 μm). During all the measurements, the top Ta electrodes were biased while the bottom Pt electrodes were grounded. (b) A typical I-V curve from the 10 by 10 μm² crossbar device showing the resistive switching behavior; the black arrows indicate the switching directions. After the forming process, the device stays in ON state. It can then be reset with a negative voltage sweep and then set with a positive voltage sweep. (c) The device can be repeatedly switched between HRS and LRS with 5 ns pulses (SET: 2.2 V; RESET: −4 V) indicating faster than 5 ns switching speed. (d) 120 billion switching cycles have been demonstrated with pulses of 1.3 V/100 ns for SET and −3.05 V/100 ns for RESET. (e) Retention test at room temperature shows no evident degradation after 1 month. (f ) Retention time measured at 250, 275, 300, 325 and 350 °C. The dotted red line is the Arrhenius fitting which yields an extrapolated activation energy 1.55 eV. The extrapolated retention time at 85 °C is 70258 years, and is 10 years at 162 °C.