Redox Reactions at Cu,Ag/Ta₂O₅ Interfaces and the Effects of Ta₂O₅ Film Density on the Forming Process in Atomic Switch Structures

Cu and Ag redox reactions at the interfaces with Ta₂O₅ and the impact of Ta₂O₅ film density on the forming process of Cu,Ag/Ta₂O₅/Pt atomic switch structures are investigated. Cyclic voltammetry measurements revealed that under positive bias to the Cu (Ag) electrode, Cu is preferentially oxidized to Cu²⁺, while Ag is oxidized to Ag⁺ ions. Subsequent negative bias causes a reduction of oxidized Cu (Ag) ions at the interfaces. The diffusion coefficient of the Cu and Ag ions in the Ta₂O₅ film is estimated from the results from different bias voltage sweep rates. It is also found that the redox current is enhanced and the forming voltage of the Cu/Ta₂O₅/Pt cell is reduced when the density of the Ta₂O₅ film is decreased. This result indicates the importance of the structural properties of the matrix oxide film in understanding and controlling resistive switching behavior. Redox reactions at the Ag,Cu/Ta₂O₅ interfaces and the impacts of Ta₂O₅ film density on the electroforming process of Ag,Cu/Ta₂O₅/Pt structures are clarified. When the density of the Ta₂O₅ film is decreased, the redox current is enhanced and the forming voltage is reduced. This finding contributes to a detailed understanding and control of the resistive switching behavior of oxide-based atomic switches.