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.
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