Write-once-read-many-times characteristics of CuO layer with Ag conductive bridges

Abstract

This paper demonstrates write-once-read-many-times (WORM) behavior of an Ag/CuO/n+-Si memory device. The CuO resistive switching layer with a thickness of 9.7 nm was prepared using a sol–gel process. The device shows a low conduction current of 10−10 A at a read voltage of 1 V. A sudden current increase is observed when the voltage increases to ∼3 V, corresponding to a resistance switching from a high-resistance state (HRS) to a low-resistance state (LRS). After that, the device remains in the LRS. Degradation of the HRS and the LRS is not observed for 104 read cycles. The HRS/LRS resistance ratio is 106, and the data retention time is over 105 s. The abrupt current increase cannot be triggered by a negative bias. The formation of Ag conductive bridges in the CuO layer is responsible for the resistance switching. Statistical analyses are performed to study the distributions of the set voltages and the resistances in the HRS and LRS. The effect of the compliance current on the operating current of the Ag/CuO/n+-Si WORM memory is also investigated. The carrier transport mechanisms are found to be dominated by Schottky emission, Ohmic, and SCLC conductions. The energy barrier is 1.066 eV, which is extracted by Schottky emission analysis.