Stabilization of Interfacial Polarization and Induction of Polarization Hysteresis in Organic MISIM Devices

Molecule-based ferroelectrics has attracted much attention because of its advantages, such as flexibility, light weight, and low environmental load. In the present work, we examined an organic metal|insulator|semiconductor|insulator|metal (MISIM) device structure to stabilize the interfacial polarization in the S layer and to induce polarization hysteresis even without bulk ferroelectrics. The MISIM devices with I = parylene C and S = TMB (=3,3',5,5'-tetramethylbenzidine)-TCNQ (=tetracyanoquinodimethane) exhibited hysteresis loops in the polarization-voltage (P-V) curves not only at room temperature but also over a wide temperature range down to 80 K. The presence of polarization hysteresis for MISIM devices was theoretically confirmed by an electrostatic model, which also explained the observed thickness dependence of the I layers on the P-V curves. Polarization hysteresis curves were also obtained in MISIM devices using typical organic semiconductors (ZnPc, C₆₀, and TCNQ) as the S layer, demonstrating the versatility of the interfacial polarization mechanism.