Composition of thin Ta₂O₅ films deposited by different methods and the effect of humidity on their resistive switching behavior

The resistive switching behavior of Cu/Ta₂O₅/Pt atomic switches, in which the Ta₂O₅ film was deposited by electron-beam (EB) evaporation and radio-frequency sputtering (SP), was investigated under different relative humidity (RH) levels. Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy measurements revealed that both films possess the oxygen-rich composition and higher water absorption capability of EB films. The Cu/Ta₂O₅-SP/Pt cell showed a stable, nonvolatile switching behavior in the observed RH range, whereas the Cu/Ta₂O₅-EB/Pt cell exhibited a similar behavior up to 50% RH, but altered from nonvolatile to volatile switching at higher RH levels. The observed volatile switching behavior of the Cu/Ta₂O₅-EB/Pt cell can be explained by increased ion migration, assisted by absorbed water and/or proton conduction in hydrated environments. The results indicate that the water uptake ability of the matrix film plays a crucial role in determining the resistive switching behavior of oxide-based atomic switches.