Fig. 3

Schematic of the switching process of the Ni/GeO_x/p⁺-Si ReRAM device (larger sign denotes larger bias). a Pristine state. b Ni²⁺ ions (gray circles) move toward the p⁺ Si bottom electrode and undergoes reduction to form Ni atoms (red circles), by which a conductive filament is formed and grows toward the Ni top electrode. c Conductive filament touches the top electrode (LRS). d Rupture of the conductive filament due to the application of opposite polarity bias voltage (HRS)