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 Ta 2 O 5 and the impact of Ta 2 O 5 film density on the forming process of Cu,Ag/Ta 2 O 5 /Pt atomic switch structures are investigated. Cyclic voltammetry measurements revealed that under positive bias to the Cu (Ag) electrode, Cu is preferentially oxidized to Cu 2+ , 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 Ta 2 O 5 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/Ta 2 O 5 /Pt cell is reduced when the density of the Ta 2 O 5 film is decreased. This result indicates the importance of the structural properties of the matrix oxide film in understanding and controlling resistive switching behavior.