A Relationship Between the Schottky Emission Mechanism and the Energy Bands of Thin-Film Metal-Insulator-Metal Configuration

Abstract

The room‐temperature current‐voltage characteristics for thermally grown Al₂O₃ dielectric films sandwiched between the Al base electrode and the Zn, Sn, or Au counter electrode were studied. Experimentally, voltage ranges were found for which the Schottky mechanism appears to be dependent on the energy band structure of the metal‐insulator‐metal configuration. The film current changes from a log J‐V^½ (the Schottky mechanism) dependency to a log J‐V dependency at a particular applied voltage V_B. Empirically, the sum φ+eV_B=ψ, where φ is the metal‐insulator barrier, is in agreement with the work function ψ of the positive metal electrode. In consideration of this ad hoc agreement, the contact potential ψ_CP=Δφ+ΔeV_B, where Δφ is the difference (asymmetry) in the calculated metal‐insulator barrier for positive and negative polarities, and ΔeV_B is the difference in the voltages for the change of mechanisms for the corresponding polarities. The mechanism by which the film currents change from the Schottky emission to the log J‐V dependency at a particular voltage V_B is not understood.