Demonstrating the Ultrathin Metal–Insulator– Metal Diode Using TiN/ZrO 2 –Al 2 O 3 –ZrO 2 Stack by Employing RuO 2 Top Electrode

Metal–insulator–metal (MIM) diodes with ultrathin insulators are highly promising for a variety of applications, such as vertical integration technology. However, MIM diodes with thin enough structures have not been achieved in previous studies on diodes using Schottky emission or tunneling conduction asymmetry. In this paper, we demonstrate an MIM diode with an ultrathin, 5-nm ZrO 2 /Al 2 O 3 /ZrO 2 insulator, using the work-function difference between the top and bottom electrodes. The rectifying properties of the diode were enhanced by employing RuO 2 as an electrode, due to its high work function and the catalytic effect on oxygen decomposition, contributing to the suppression of trap-assisted tunneling. This paper presents an important development in understanding MIM structures with respect to the electrical and chemical properties.