Structural phase transition and resistive switching properties of Cu_xO films during post-thermal annealing

We studied the phase change and resistive switching characteristics of copper oxide (Cu_xO) films through post-thermal annealing. This investigation aimed to assess the material's potential for a variety of electrical devices, exploring its versatility in electronic applications. The Cu_xO films deposited by RF magnetron sputtering were annealed at 300, 500, and 700 °C in ambient air for 4 min by rapid thermal annealing (RTA) method, and then it was confirmed that the structural phase change from Cu₂O to CuO occurred with increasing annealing temperature. Resistive random-access memory (ReRAM) devices with Au/Cu_xO/p⁺-Si structures were fabricated, and the ReRAM properties appeared in CuO-based devices, while Cu₂O ReRAM devices did not exhibit resistive switching behavior. The CuO ReRAM device annealed at 500 °C showed the best properties, with a on/off ratio of 8 × 10², good switching endurance of ∼100 cycles, data retention for 10⁴s, and stable uniformity in the cumulative probability distribution. This characteristic change could be explained by the difference in the grain size and density of defects between the Cu₂O and CuO films. These results demonstrate that superior and stable resistive switching properties of RF-sputtered Cu_xO films can be obtained by low-temperature RTA.