Metal-insulator-metal diodes: role of the insulator layer on the rectification performance.

Metal–Insulator–Metal (MIM) diodes are actively investigated as high-frequency rectifi ers [ 2 , 4 , 15–18 ] for these applications, complemented by other related devices such as metal/double-insulator/ metal (MIIM) diodes, [ 13 , 19 ] geometric diodes, [ 20 , 21 ] and molecular diodes. [ 22 , 23 ] Quantum-based electron-transport (tunneling based) are targeted for the rectifi cation mechanism in suitably designed MIM structures [ 24 ] because the tunneling process yields time constants in the range of femto seconds (10 − 15 s). A well-designed MIM structures can therefore potentially rectify frequencies as high as 10 15 Hz. Signifi cant progress has been made to fabricate nano-sized MIM diodes, a geometric requirement for THz frequency applications. [ 15 , 16 ] For MIM systems, numerous works have been reported which provide an understanding of the transport mechanism, [ 25 , 26 ] the theory of device operation [ 27 , 28 ] and suitability of MIM for energy harvesting applications. [ 29 ] However, systematic experimental studies to correlate material properties to MIM rectifi cation performance have been largely absent. Consequently, materials-design rules to help choose suitable materials for the MIM stack that favor the desired rectifi cation behavior are lacking. In a recent review article, Miskovsky et al., highlighted the importance of investigating material properties and designing new materials to optimize MIM high-frequency rectifi cation performance. [ 30 ]