Reversible Rectification of Microscale Ferroelectric Junctions Employing Liquid Metal Electrodes

Both ferroelectric crystals and liquid metal electrodes have attracted extensive attention for potential applications in next-generation devices and circuits. However, the interface information between ferroelectric crystals and liquid metal electrodes has so far been lacking. To better understand the optoelectronic properties of microscale ferroelectric crystals (potassium tantalate niobate, KTN) and its potential integration with liquid metal electrodes (a "printing ink" for flexible electric circuit production), microscale KTN crystals sandwiched by eutectic gallium indium (EGaIn, a liquid metal) with varied contact geometries were studied. Unlike the bulk KTN crystal junctions, the microscale KTN junctions show electrical rectifying characteristics upon light illumination, and the directionality of the rectification can be reversed by increasing the ambient temperature to a few degrees. Furthermore, a strong suppression of the current upon increasing voltage, that is, the quasi-negative differential resistance, is observed when the microscale KTN is half-enclosed by the EGaIn electrode. Our results show that trapping/detrapping of carriers affected by the crystal size and the ambient temperature is the dominant physical mechanism for these observations. These results not only facilitate a better understanding of charge transport through the microscale ferroelectric crystals but also advance the design of miniaturized hybrid devices.