Repeatable unipolar/bipolar resistive memory characteristics and switching mechanism using a Cu nanofilament in a GeOx film

This paper investigates the repeatable unipolar/bipolar resistive switching memory characteristics in a copper/germanium-oxide/tungsten (Cu/GeOx/W) structure. The switching mechanism occurs because of the lower barrier height for hole injection rather than electron injection. Therefore, Cu ions, as a positive charge, migrate before initiating growth at the GeOx/W interface and dissolving at the GeOx/Cu interface. The diameter of the Cu nanofilament increases linearly from 0.13 Aa to 25 nm as current compliances increase from 1 nA to 10 mA, as calculated using the other approach. The crystalline Cu nanofilament was also confirmed by high-resolution transmission electron microscopy analysis under SET. Good data retention with high resistance ratios of 102-105 (and >104 at 85 degree C) and similar to 109 was obtained under the bipolar and unipolar modes, respectively. Therefore, a maximum memory size of 5000 Pbit/in2 can be designed in the future.