Fig. 1
From: Conductance Quantization in Resistive Random Access Memory
Schematic I–V curves of resistive switching process in a CF-type bipolar RRAM device. Insets A–C show the different resistance states of the device during the switching process. In most cases, the fresh RRAM device shows a very high initial resistance state (IRS) with few defects (inset A). In a positive bias sweep, when the voltage increases to a comparative high voltage (V Forming), the device switches to the low resistance state (LRS) with a conducting filament formed in the RS layer (inset B). Then, in a negative voltage sweep, when the voltage reaches a critical value (V RESET), the device switches from LRS to the high resistance state (HRS), corresponding to a RESET transition in which the CF is ruptured (inset C). At last, in another positive sweep, the device will switch to LRS again, with the filament reconnected (inset B). This process is called as SET, with the SET voltage (V SET) much lower than (V Forming). If the device has a good endurance, the above SET and RESET switching can be reproducibly and successively carried out for a large number of cycles